Solaris Developer Glossary

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Symbols, appended to a term, designates the following:

|| = associated with parallel processing
ˆ = associated with Sun Studio specifically

access control list (ACL): Access control list (ACL) provides greater control over file and folder permissions. ACL enables you to define file or folder permissions for the owner, owner's group, others, and specific users and groups. It lists default permissions for each of these categories.
accuracy ˆ: A measure of how well one number approximates another. For example, the accuracy of a computed result often reflects the extent to which errors in the
computation cause it to differ from the mathematically exact result. Accuracy can be expressed in terms of significant digits (e.g., "The result is
accurate to six digits") or more generally in terms of the preservation of relevant mathematical properties (e.g., "The result has the correct
algebraic sign").
AC Fail: An abnormal event related to the AC power supply, such as a power outage. Inconventional usage, it can refer to DC power supply systems as well.
ACL: See access control list.
AC ok (ACOK): A signal to check the status of the power supply. AC ok is normal operational status. "AC ok."
ACOK: See AC ok.
AC on (ACON): Status of AC power supply when receiving input.
ACON: See AC on.
ACS: See AC section.
AC Section (ACS): Generic term for parts of the AC input, circuit breaker and filter in the power supply.
active domain: A domain running operating system (OS) software.
active removal/replacement: The board is being actively used by the domain to which it is assigned. To remove and install a board which is being actively used by the domain, the service provider must DR the board out of the domain. Then, the service provider can remove the board.
application client module: A software unit that consists of one or more classes and an application client deployment descriptor.
activity: A combination of discrete tasks that has a clearly defined beginning and end. A group of tasks that are carried out as part of a process.
agent: A computer program that enables the automation of a well defined activity by performing a specific well defined task when it detects a predetermined set of conditions.
air filter: A mesh assembly on the system used to remove dust from the air that passes through it.
alive check interrupt: Interruption of the normal Solaris operating system environment indicator, readable from the service processor. Absence of heartbeat updates for a running Solaris system usually indicates a Solaris software hang.
aggregation: A combination of information from one or more sources.
analysis system: An application that allows manipulation of data (e.g., what-if analysis and forecasting) from other applications. This is a type of Decision Support System (DSS) that creates new authoritative data that can be used in other operational applications.
APCS: See Auto Power Control System.
Application: A program or collection of programs that facilitate one or more activities frequently through a user interface. Applications typically manage, transform, and/or distribute data.
Application Model: The application integration architecture from both a conceptual and actual perspective.
Application: A program or collection of programs that facilitate one or more activities frequently through a user interface. Applications typically manage, transform, and/or distribute data.
Application Programming Interface (API): An API is a semi-formal description of standard inputs and outputs supported by a particular application, service, or protocol.
Application Server: Hosts and manages distributed logic and supports services, such as: high performance data access, transaction management, distribution state and session management, request brokering, dynamic load balancing and fault tolerance. The application server is frequently viewed as part of a n-tier architecture, consisting of a web server, application server, integration server and database server, etc.
arbitration stop ˆ: A condition that occurs when one of the OPL system ASICs detects a parity error or equivalent fatal system error. Bus arbitration is frozen, so all bus activity stops.
array processing||: A number of processors working simultaneously, each handling one element of the array, so that a single operation can apply to all elements of the
array in parallel.
ASIC: An acronym for application-specific integrated circuit. Any of the functionally complex chips in the OPL hardware design.
assign: In DR User's Guide, "assign" means the operation to set operating conditions of a system board, and to register it to be DCL (Domain Component List) database. This operation makes the system board available to domains.
associativity||: See cache, direct mapped cache, fully associative cache, set associative cache.
ASR: See automatic system recovery.
asynchronous control|| ˆ: Computer control behavior where a specific operation is begun upon receipt of an indication (signal) that a particular event has occurred. Asynchronous control relies on synchronization mechanisms called locks to coordinate processors. See also mutual exclusion, mutex lock, semaphore lock, single-lock strategy, spin lock.
AT: Advanced technology.
ATAPI: AT Attachment Packet Interface.
AT Attachment Packet Interface: An interface between the computer and attached CD-ROM and tape backup drives.
attachment point: A collective term for a board and its card cage slot. A physical attachment point describes the software driver and location of the card cage slot. A logical attachment point is an abbreviated name created by the system to see the physical attachment point.
audit: The collection of data about the use of system resources. Auditing provides a record of security-related system events. This term is used in XSCF firmware.
audit configuration: Functional arrangement of the auditing capability. This term is used in XSCF firmware.
audit class: A grouping of audit events. Audit classes provide a way to select a group of events to audit. This term is used in XSCF firmware.
audit event: A security-related system action that is audited. Events are grouped into classes. This term is used in XSCF firmware.
audit file: An audit log where audit records are stored. This term is used in XSCF firmware.
audit policy: A set of auditing options that an administrator can enable or disable. These options include which events will be recorded and whether to record certain kinds of audit data. The options also include whether to suspend audible actions when the audit trail is full. This term is used in XSCF firmware.
audit record: Audit data that is stored in an audit file. An audit record describes a single audit event. Each audit record is composed of audit tokens. This term is used in XSCF firmware.
Audit Trail: An audit trail contains one record for each logged activity/event. It is a chronological record that enables the reconstruction, review, and examination of a sequence of activities.
Authenticate: To verify the identity of a user, device, or other entity in a computer system, often a prerequisite to allowing access to resources in a system. Based on definition found at search Database.com see http://searchdatabase.techtarget.com
authentication: A method by which a system validates and authorizes a user or function to access or use the system.
Authenticate: To verify the identity of a user, device, or other entity in a computer system, often a prerequisite to allowing access to resources in a system. Based on definition found at search Database.com see http://searchdatabase.techtarget.com
authorization: The ability to perform an operation, act, or function with a computer resource (for example, run, modify or show). The means by which the ability is explicitly enabled or restricted in some way.
Authorization: The process of determining whether a user, device, or other entity is allowed to access a particular resource or a predetermined function (within a resource) via a specific access method. Based on definition found at http://www.csgnetwork.com/glossaryl.html
automatic system recovery (ASR): The procedures that restore the system to running all properly configured domains after one or more domains have been rendered inactive due to software or hardware failures or due to unacceptable environmental conditions.
Auto Power Control System (APCS): The function which automatically powers the system on/off according to the predesignated operation schedule.
Availability: A measure of when an application, system, database or service is available for use.

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B2B: Business-to-business.
backing bean: A JavaBeans component that corresponds to a JSP page that includes JavaServer Faces components. The backing bean defines properties for the components on the page and methods that perform processing for the component. This processing includes event handling, validation, and processing associated with navigation.
barrier|| ˆ: A synchronization mechanism for coordinating tasks even when data accesses are not involved. A barrier is analogous to a gate. Processors or threads
operating in parallel reach the gate at different times, but none can pass through until all processors reach the gate. For example, suppose at the end
of each day, all bank tellers are required to tally the amount of money that was deposited, and the amount that was withdrawn. These totals are then
reported to the bank vice president, who must check the grand totals to verify debits equal credits. The tellers operate at their own speeds; that is,
they finish totaling their transactions at different times. The barrier mechanism prevents tellers from leaving for home before the grand total is
checked. If debits do not equal credits, all tellers must return to their desks to find the error. The barrier is removed after the vice president
obtains a satisfactory grand total.
basic authentication: An authentication mechanism in which a Web server authenticates an entity via a user name and password obtained using the Web application's built-in authentication mechanism.
bean-managed persistence: The mechanism whereby data transfer between an entity bean's variables and a resource manager is managed by the entity bean.
bean-managed transaction: A transaction whose boundaries are defined by an enterprise bean.
biased exponent ˆ: The sum of the base-2 exponent and a constant (bias) chosen to make the stored exponent's range non-negative. For example, the exponent of 2^-100 is stored in IEEE single precision format as (-100) + (single precision bias of 127) = 27.
binade ˆ: The interval between any two consecutive powers of two.
binary entity: See unparsed entity.
binding (XML): Generating the code needed to process a well-defined portion of XML data.
binding (JavaServer Faces technology): Wiring UI components to back-end data sources such as backing bean properties.
blocked state|| ˆ: A thread is waiting for a resource or data; such as, return data from a pending disk read, or waiting for another thread to unlock a resource.
bound threads|| ˆ: For Solaris threads, a thread permanently assigned to a particular LWP is called a bound thread. Bound threads can be scheduled on a real-time basis in strict priority with respect to all other active threads in the system, not only within a process. An LWP is an entity that can be scheduled with the same default scheduling priority as any UNIX process.
build file: The XML file that contains one or more asant targets. A target is a set of tasks you want to be executed. When starting asant, you can select which targets you want to have executed. When no target is given, the project's default target is executed.
business logic: The code that implements the functionality of an application. In the Enterprise JavaBeans architecture, this logic is implemented by the methods of an enterprise bean.
business method: A method of an enterprise bean that implements the business logic or rules of an application.

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cache|| ˆ: Small, fast, hardware-controlled memory that acts as a buffer between a processor and main memory. Cache contains a copy of the most recently used memory locations--addresses and contents--of instructions and data. Every address reference goes first to cache. If the desired instruction or data is not in cache, a cache miss occurs. The contents are fetched across the bus from main memory into the CPU register specified in the instruction being executed and a copy is also written to cache. It is likely that the same location will be used again soon, and, if so, the address is found in cache, resulting in a cache hit. If a write to that address occurs, the hardware not only writes to cache, but can also generate a write-through to main memory.

See also associativity, circuit switching, direct mapped cache, fully associative cache, MBus, packet switching, set associative cache, write-back, write-through, XDBus.
cache locality|| ˆ: A program does not access all of its code or data at once with equal probability. Having recently accessed information in cache increases the probability of finding information locally without having to access memory. The principle of locality states that programs access a relatively small portion of their address space at any instant of time. There are two different types of locality: temporal and spatial.

Temporal locality (locality in time) is the tendency to reuse recently accessed items. For example, most programs contain loops, so that instructions and data are likely to be accessed repeatedly. Temporal locality retains recently accessed items closer to the processor in cache rather than requiring a memory access. See also cache, competitive-caching, false sharing, write-invalidate, write-update.

Spatial locality (locality in space) is the tendency to reference items whose addresses are close to other recently accessed items. For example, accesses to elements of an array or record show a natural spatial locality. Caching takes advantage of spatial locality by moving blocks (multiple contiguous words) from memory into cache and closer to the processor. See also cache, competitive-caching, false sharing, write-invalidate, write-update.
callback methods: Component methods called by the container to notify the component of important events in its life cycle.
caller: Same as caller principal.
caller principal: The principal that identifies the invoker of the enterprise bean method.
cascade delete: A deletion that triggers another deletion. A cascade delete can be specified for an entity bean that has container-managed persistence.
CDATA: A predefined XML tag for character data that means "don't interpret these characters," as opposed to parsed character data (PCDATA), in which the normal rules of XML syntax apply. CDATA sections are typically used to show examples of XML syntax.
certificate authority: A trusted organization that issues public key certificates and provides identification to the bearer.
chaining ˆ: A hardware feature of some pipeline architectures that allows the result of an operation to be used immediately as an operand for a second operation, simultaneously with the writing of the result to its destination register. The total cycle time of two chained operations is less than the sum of the stand-alone cycle times for the instructions. For example, the TI 8847 supports chaining of consecutive fadd, fsub, and fmul (of the same precision). Chained faddd/fmuld requires 12 cycles, while consecutive unchained faddd/fmuld requires 17 cycles.
circuit switching|| ˆ: A mechanism for caches to communicate with each other as well as with main memory. A dedicated connection (circuit) is established between caches or between cache and main memory. While a circuit is in place no other traffic can travel over the bus.
client-certificate authentication: An authentication mechanism that uses HTTP over SSL, in which the server and, optionally, the client authenticate each other with a public key certificate that conforms to a standard that is defined by X.509 Public Key Infrastructure.
coherence|| ˆ: In systems with multiple caches, the mechanism that ensures that all processors see the same image of memory at all times.
comment: In an XML document, text that is ignored unless the parser is specifically told to recognize it.
commit: The point in a transaction when all updates to any resources involved in the transaction are made permanent.
common exceptions ˆ: The three floating point exceptions overflow, invalid, and division are collectively referred to as the common exceptions for the purposes of ieee_flags(3m) and ieee_handler(3m). They are called common exceptions because they are commonly trapped as errors.
competitive-caching|| ˆ: Competitive-caching maintains cache coherence by using a hybrid of write-invalidate and write-update. Competitive-caching uses a counter to age shared data. Shared data is purged from cache based on a least-recently-used (LRU) algorithm. This can cause shared data to become private data again, thus eliminating the need for the cache coherency protocol to access memory (via backplane bandwidth) to keep multiple copies synchronized. See also cache, cache locality, false sharing, write-invalidate, write-update.
component: See J2EE component.
component (JavaServer Faces technology): See JavaServer Faces UI component.
component contract: The contract between a J2EE component and its container. The contract includes life-cycle management of the component, a context interface that the instance uses to obtain various information and services from its container, and a list of services that every container must provide for its components.
concurrency|| ˆ: The execution of two or more active threads or processes in parallel. On a uniprocessor apparent concurrence is accomplished by rapidly switching between threads. On a multiprocessor system true parallel execution can be achieved. See also asynchronous control, multiprocessor system, thread.
concurrent processes|| ˆ: Processes that execute in parallel in multiple processors or asynchronously on a single processor. Concurrent processes can interact with each other, and one process can suspend execution pending receipt of information from another process or the occurrence of an external event. See also process, sequential processes.
condition variable|| ˆ: For Solaris threads, a condition variable enables threads to atomically block until a condition is satisfied. The condition is tested under the protection of a mutex lock. When the condition is false, a thread blocks on a condition variable and atomically releases the mutex waiting for the condition to change. When another thread changes the condition, it can signal the associated condition variable to cause one or more waiting threads to wake up, reacquire the mutex, and re-evaluate the condition. Condition variables can be used to synchronize threads in this process and other processes if the variable is allocated in memory that is writable and shared among the cooperating processes and have been initialized for this behavior.
component-managed sign-on: A mechanism whereby security information needed for signing on to a resource is provided by an application component.
connection: See resource manager connection.
connection factory: See resource manager connection factory.
connector: A standard extension mechanism for containers that provides connectivity to enterprise information systems. A connector is specific to an enterprise information system and consists of a resource adapter and application development tools for enterprise information system connectivity. The resource adapter is plugged in to a container through its support for system-level contracts defined in the Connector architecture.
Connector architecture: An architecture for integration of J2EE products with enterprise information systems. There are two parts to this architecture: a resource adapter provided by an enterprise information system vendor and the J2EE product that allows this resource adapter to plug in. This architecture defines a set of contracts that a resource adapter must support to plug in to a J2EE product-for example, transactions, security, and resource management.
container: An entity that provides life-cycle management, security, deployment, and runtime services to J2EE components. Each type of container (EJB, Web, JSP, servlet, applet, and application client) also provides component-specific services.
container-managed persistence: The mechanism whereby data transfer between an entity bean's variables and a resource manager is managed by the entity bean's container.
container-managed sign-on: The mechanism whereby security information needed for signing on to a resource is supplied by the container.
container-managed transaction: A transaction whose boundaries are defined by an EJB container. An entity bean must use container-managed transactions.
content: In an XML document, the part that occurs after the prolog, including the root element and everything it contains.
context ˆ: In multitasking operating systems, such as the SunOStrademark operating system, processes run for a fixed time quantum. At the end of the time quantum, the CPU receives a signal from the timer, interrupts the currently running process, and prepares to run a new process. The CPU saves the registers for the old process, and then loads the registers for the new process. Switching from the old process state to the new is known as a context switch. Time spent switching contexts is system overhead; the time required depends on the number of registers, and on whether there are special instructions to save the registers associated with a process.
context attribute: An object bound into the context associated with a servlet.
context root: A name that gets mapped to the document root of a Web application.
context switch ˆ: In multitasking operating systems, such as the SunOS operating system, processes run for a fixed time quantum. At the end of the time quantum, the CPU receives a signal from the timer, interrupts the currently running process, and prepares to run a new process. The CPU saves the registers for the old process, and then loads the registers for the new process. Switching from the old process state to the new is known as a context switch. Time spent switching contexts is system overhead; the time required depends on the number of registers, and on whether there are special instructions to save the registers associated with a process.
control flow model|| ˆ: The von Neumann model of a computer. This model specifies flow of control; that is, which instruction is executed at each step of a program. All Sun workstations are instances of the von Neumann model. See also data flow model, demand-driven dataflow.
conversational state: The field values of a session bean plus the transitive closure of the objects reachable from the bean's fields. The transitive closure of a bean is defined in terms of the serialization protocol for the Java programming language, that is, the fields that would be stored by serializing the bean instance.
CORBA: Common Object Request Broker Architecture. A language-independent distributed object model specified by the OMG.
create method: A method defined in the home interface and invoked by a client to create an enterprise bean.
credentials: The information describing the security attributes of a principal.
critical region|| ˆ: An indivisible section of code that can only be executed by one thread at a time and is not interruptible by other threads; such as, code that accesses a shared variable. See also mutual exclusion, mutex lock, semaphore lock, single-lock strategy, spin lock.
critical resource|| ˆ: A resource that can only be in use by at most one thread at any given time. Where several asynchronous threads are required to coordinate their access to a critical resource, they do so by synchronization mechanisms. See also mutual exclusion, mutex lock, semaphore lock, single-lock strategy, spin lock.
CSS: Cascading style sheet. A stylesheet used with HTML and XML documents to add a style to all elements marked with a particular tag, for the direction of browsers or other presentation mechanisms.
CTS: Compatibility test suite. A suite of compatibility tests for verifying that a J2EE product complies with the J2EE platform specification.

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data: The contents of an element in an XML stream, generally used when the element does not contain any subelements. When it does, the term content is generally used. When the only text in an XML structure is contained in simple elements and when elements that have subelements have little or no data mixed in, then that structure is often thought of as XML data, as opposed to an XML document.
data flow model|| ˆ: This computer model specifies what happens to data, and ignores instruction order. That is, computations move forward by nature of availability of data values instead of the availability of instructions. See also control flow model, demand-driven dataflow.
data race|| ˆ: In multithreading, a situation where two or more threads simultaneously access a shared resource. The results are indeterminate depending on the order in which the threads accessed the resource. This situation, called a data race, can produce different results when a program is run repeatedly with the same input. See also mutual exclusion, mutex lock, semaphore lock, single-lock strategy, spin lock.
DDP: Document-driven programming. The use of XML to define applications.
default result ˆ: The value that is delivered as the result of a floating-point operation that caused an exception.
declaration: The very first thing in an XML document, which declares it as XML. The minimal declaration is <?xml version="1.0"?>. The declaration is part of the document prolog.
declarative security: Mechanisms used in an application that are expressed in a declarative syntax in a deployment descriptor.
default result ˆ: The value that is delivered as the result of a floating-point operation that caused an exception.
delegation: An act whereby one principal authorizes another principal to use its identity or privileges with some restrictions.
demand-driven dataflow|| ˆ: A task is enabled for execution by a processor when its results are required by another task that is also enabled; such as, a graph reduction model. A graph reduction program consists of reducible expressions that are replaced by their computed values as the computation progresses through time. Most of the time, the reductions are done in parallel--nothing prevents parallel reductions except the availability of data from previous reductions. See also control flow model, data flow model.
denormalized number ˆ: Older nomenclature for subnormal number.
deployer: A person who installs J2EE modules and applications into an operational environment.
deployment: The process whereby software is installed into an operational environment.
deployment descriptor: An XML file provided with each module and J2EE application that describes how they should be deployed. The deployment descriptor directs a deployment tool to deploy a module or application with specific container options and describes specific configuration requirements that a deployer must resolve.
destination: A JMS administered object that encapsulates the identity of a JMS queue or topic. See point-to-point messaging system, publish/subscribe messaging system.
digest authentication: An authentication mechanism in which a Web application authenticates itself to a Web server by sending the server a message digest along with its HTTP request message. The digest is computed by employing a one-way hash algorithm to a concatenation of the HTTP request message and the client's password. The digest is typically much smaller than the HTTP request and doesn't contain the password.
direct mapped cache|| ˆ: A direct mapped cache is a one-way set associative cache. That is, each cache entry holds one block and forms a single set with one element. See also cache, cache locality, false sharing, fully associative cache, set associative cache, write-invalidate, write-update.
distributed application: An application made up of distinct components running in separate runtime environments, usually on different platforms connected via a network. Typical distributed applications are two-tier (client-server), three-tier (client-middleware-server), and multitier (client-multiple middleware-multiple servers).
distributed memory architecture|| ˆ: A combination of local memory and processors at each node of the interconnect network topology. Each processor can directly access only a portion of the total memory of the system. Message passing is used to communicate between any two processors, and there is no global, shared memory. Therefore, when a data structure must be shared, the program issues send/receive messages to the process that owns that structure. See also interprocess communication, message passing.
document: In general, an XML structure in which one or more elements contains text intermixed with subelements. See also data.
Document Object Model: An API for accessing and manipulating XML documents as tree structures. DOM provides platform-neutral, language-neutral interfaces that enables programs and scripts to dynamically access and modify content and structure in XML documents.
document root: The top-level directory of a WAR. The document root is where JSP pages, client-side classes and archives, and static Web resources are stored.
DOM: See Document Object Model.
double precision ˆ: Using two words to represent a number in order to keep or increase precision. On SPARC? workstations, double precision is the 64-bit IEEE double precision.
DTD: Document type definition. An optional part of the XML document prolog, as specified by the XML standard. The DTD specifies constraints on the valid tags and tag sequences that can be in the document. The DTD has a number of shortcomings, however, and this has led to various schema proposals. For example, the DTD entry <!ELEMENT username (#PCDATA)> says that the XML element called username contains parsed character data-that is, text alone, with no other structural elements under it. The DTD includes both the local subset, defined in the current file, and the external subset, which consists of the definitions contained in external DTD files that are referenced in the local subset using a parameter entity.
durable subscription: In a JMS publish/subscribe messaging system, a subscription that continues to exist whether or not there is a current active subscriber object. If there is no active subscriber, the JMS provider retains the subscription's messages until they are received by the subscription or until they expire.

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EAR file: Enterprise Archive file. A JAR archive that contains a J2EE application.
ebXML: Electronic Business XML. A group of specifications designed to enable enterprises to conduct business through the exchange of XML-based messages. It is sponsored by OASIS and the United Nations Centre for the Facilitation of Procedures and Practices in Administration, Commerce and Transport (U.N./CEFACT).
EJB: See Enterprise JavaBeans.
EJB container: A container that implements the EJB component contract of the J2EE architecture. This contract specifies a runtime environment for enterprise beans that includes security, concurrency, life-cycle management, transactions, deployment, naming, and other services. An EJB container is provided by an EJB or J2EE server.
EJB container provider: A vendor that supplies an EJB container.
EJB context: An object that allows an enterprise bean to invoke services provided by the container and to obtain the information about the caller of a client-invoked method.
EJB home object: An object that provides the life-cycle operations (create, remove, find) for an enterprise bean. The class for the EJB home object is generated by the container's deployment tools. The EJB home object implements the enterprise bean's home interface. The client references an EJB home object to perform life-cycle operations on an EJB object. The client uses JNDI to locate an EJB home object.
EJB JAR file: A JAR archive that contains an EJB module.
EJB module: A deployable unit that consists of one or more enterprise beans and an EJB deployment descriptor.
EJB object: An object whose class implements the enterprise bean's remote interface. A client never references an enterprise bean instance directly; a client always references an EJB object. The class of an EJB object is generated by a container's deployment tools.
EJB server: Software that provides services to an EJB container. For example, an EJB container typically relies on a transaction manager that is part of the EJB server to perform the two-phase commit across all the participating resource managers. The J2EE architecture assumes that an EJB container is hosted by an EJB server from the same vendor, so it does not specify the contract between these two entities. An EJB server can host one or more EJB containers.
EJB server provider: A vendor that supplies an EJB server.
element: A unit of XML data, delimited by tags. An XML element can enclose other elements.
empty tag: A tag that does not enclose any content.
enterprise bean: A J2EE component that implements a business task or business entity and is hosted by an EJB container; either an entity bean, a session bean, or a message-driven bean.
enterprise bean provider: An application developer who produces enterprise bean classes, remote and home interfaces, and deployment descriptor files, and packages them in an EJB JAR file.
enterprise information system: The applications that constitute an enterprise's existing system for handling companywide information. These applications provide an information infrastructure for an enterprise. An enterprise information system offers a well-defined set of services to its clients. These services are exposed to clients as local or remote interfaces or both. Examples of enterprise information systems include enterprise resource planning systems, mainframe transaction processing systems, and legacy database systems.
enterprise information system resource: An entity that provides enterprise information system-specific functionality to its clients. Examples are a record or set of records in a database system, a business object in an enterprise resource planning system, and a transaction program in a transaction processing system.
Enterprise JavaBeans (EJB): A component architecture for the development and deployment of object-oriented, distributed, enterprise-level applications. Applications written using the Enterprise JavaBeans architecture are scalable, transactional, and secure.
Enterprise JavaBeans Query Language (EJB QL): Defines the queries for the finder and select methods of an entity bean having container-managed persistence. A subset of SQL92, EJB QL has extensions that allow navigation over the relationships defined in an entity bean's abstract schema.
entity: A distinct, individual item that can be included in an XML document by referencing it. Such an entity reference can name an entity as small as a character (for example, <, which references the less-than symbol or left angle bracket, <). An entity reference can also reference an entire document, an external entity, or a collection of DTD definitions.
entity bean: An enterprise bean that represents persistent data maintained in a database. An entity bean can manage its own persistence or can delegate this function to its container. An entity bean is identified by a primary key. If the container in which an entity bean is hosted crashes, the entity bean, its primary key, and any remote references survive the crash.
entity reference: A reference to an entity that is substituted for the reference when the XML document is parsed. It can reference a predefined entity such as < or reference one that is defined in the DTD. In the XML data, the reference could be to an entity that is defined in the local subset of the DTD or to an external XML file (an external entity). The DTD can also carve out a segment of DTD specifications and give it a name so that it can be reused (included) at multiple points in the DTD by defining a parameter entity.
error: A SAX parsing error is generally a validation error; in other words, it occurs when an XML document is not valid, although it can also occur if the declaration specifies an XML version that the parser cannot handle. See also fatal error, warning.
exception ˆ: An arithmetic exception arises when an attempted atomic arithmetic operation has no result that is acceptable universally. The meanings of atomic and acceptable vary with time and place.
exponent ˆ: The component of a floating-point number that signifies the integer power to which the base is raised in determining the value of the represented number.
Extensible Markup Language: See XML.
external entity: An entity that exists as an external XML file, which is included in the XML document using an entity reference.
external subset: That part of a DTD that is defined by references to external DTD files.

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false sharing|| ˆ: A condition that occurs in cache when two unrelated data accessed independently by two threads reside in the same block. This block can end up 'ping-ponging' between caches for no valid reason. Recognizing such a case and rearranging the data structure to eliminate the false sharing greatly increases cache performance. See also cache, cache locality.
fatal error: A fatal error occurs in the SAX parser when a document is not well formed or otherwise cannot be processed. See also error, warning.
filter: An object that can transform the header or content (or both) of a request or response. Filters differ from Web components in that they usually do not themselves create responses but rather modify or adapt the requests for a resource, and modify or adapt responses from a resource. A filter should not have any dependencies on a Web resource for which it is acting as a filter so that it can be composable with more than one type of Web resource.
filter chain: A concatenation of XSLT transformations in which the output of one transformation becomes the input of the next.
finder method: A method defined in the home interface and invoked by a client to locate an entity bean.
form-based authentication
floating-point number system ˆ: A system for representing a subset of real numbers in which the spacing between representable numbers is not a fixed, absolute constant. Such a system is characterized by a base, a sign, a significand, and an exponent (usually biased). The value of the number is the signed product of its significand and the base raised to the power of the unbiased exponent.
form-based authentication: An authentication mechanism in which a Web container provides an application-specific form for logging in. This form of authentication uses Base64 encoding and can expose user names and passwords unless all connections are over SSL.
fully associative cache|| ˆ: A fully associative cache with m entries is an m-way set associative cache. That is, it has a single set with m blocks. A cache entry can reside in any of the m blocks within that set. See also cache, cache locality, direct mapped cache, false sharing, set associative cache, write-invalidate, write-update.

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general entity: An entity that is referenced as part of an XML document's content, as distinct from a parameter entity, which is referenced in the DTD. A general entity can be a parsed entity or an unparsed entity.
gradual underflow ˆ: When a floating-point operation underflows, return a subnormal number instead of 0. This method of handling underflow minimizes the loss of accuracy in floating-point calculations on small numbers.
group: An authenticated set of users classified by common traits such as job title or customer profile. Groups are also associated with a set of roles, and every user that is a member of a group inherits all the roles assigned to that group.

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handle: An object that identifies an enterprise bean. A client can serialize the handle and then later deserialize it to obtain a reference to the enterprise bean.
hidden bits ˆ: Extra bits used by hardware to ensure correct rounding, not accessible by software. For example, IEEE double precision operations use three hidden bits
to compute a 56-bit result that is then rounded to 53 bits.
home handle: An object that can be used to obtain a reference to the home interface. A home handle can be serialized and written to stable storage and deserialized to obtain the reference.
home interface: One of two interfaces for an enterprise bean. The home interface defines zero or more methods for managing an enterprise bean. The home interface of a session bean defines create and remove methods, whereas the home interface of an entity bean defines create, finder, and remove methods.
HTML: Hypertext Markup Language. A markup language for hypertext documents on the Internet. HTML enables the embedding of images, sounds, video streams, form fields, references to other objects with URLs, and basic text formatting.
HTTP: Hypertext Transfer Protocol. The Internet protocol used to retrieve hypertext objects from remote hosts. HTTP messages consist of requests from client to server and responses from server to client.
HTTPS: HTTP layered over the SSL protocol.

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IDL: Interface Definition Language. A language used to define interfaces to remote CORBA objects. The interfaces are independent of operating systems and programming languages.
IEEE Standard 754 ˆ: The standard for binary floating-point arithmetic developed by the Institute of Electrical and Electronics Engineers, published in 1985.
IIOP: Internet Inter-ORB Protocol. A protocol used for communication between CORBA object request brokers.
impersonation: An act whereby one entity assumes the identity and privileges of another entity without restrictions and without any indication visible to the recipients of the impersonator's calls that delegation has taken place. Impersonation is a case of simple delegation.
initialization parameter: A parameter that initializes the context associated with a servlet.
in-line template ˆ: A fragment of assembly language code that is substituted for the function call it defines, during the inlining pass of Sun Studio compilers. Used (for example) by the math library in in-line template files (libm.il) in order to access hardware implementations of trigonometric functions and other elementary functions from C programs.
interconnection network topology|| ˆ: Interconnection topology describes how the processors are connected. All networks consist of switches whose links go to processor-memory nodes and to other switches. There are four generic forms of topology: star, ring, bus, and fully-connected network. Star topology consists of a single hub processor with the other processors directly connected to the single hub, the non-hub processors are not directly connected to each other. In ring topology all processors are on a ring and communication is generally in one direction around the ring. Bus topology is noncyclic, with all nodes connected; consequently, traffic travels in both directions, and some form of arbitration is needed to determine which processor can use the bus at any particular time. In a fully-connected (crossbar) network, every processor has a bidirectional link to every other processor.

Commercially-available parallel processors use multistage network topologies. A multistage network topology is characterized by 2-dimensional grid, and
boolean n-cube.
interprocess communication|| ˆ: Message passing among active processes. See also circuit switching, distributed memory architecture, MBus, message passing, packet switching, shared
memory, XDBus.
IPC|| ˆ: See interprocess communication.
ISO 3166: The international standard for country codes maintained by the International Organization for Standardization (ISO).
ISV: Independent software vendor.

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J2EE: See Java 2 Platform, Enterprise Edition.
J2EE application: Any deployable unit of J2EE functionality. This can be a single J2EE module or a group of modules packaged into an EAR file along with a J2EE application deployment descriptor. J2EE applications are typically engineered to be distributed across multiple computing tiers.
J2EE component: A self-contained functional software unit supported by a container and configurable at deployment time. The J2EE specification defines the following J2EE components:

Application clients and applets are components that run on the client.
Java servlet and JavaServer Pages (JSP) technology components are Web components that run on the server.
Enterprise JavaBeans (EJB) components (enterprise beans) are business components that run on the server.

J2EE components are written in the Java programming language and are compiled in the same way as any program in the language. The difference between J2EE components and "standard" Java classes is that J2EE components are assembled into a J2EE application, verified to be well formed and in compliance with the J2EE specification, and deployed to production, where they are run and managed by the J2EE server or client container.

J2EE module: A software unit that consists of one or more J2EE components of the same container type and one deployment descriptor of that type. There are four types of modules: EJB, Web, application client, and resource adapter. Modules can be deployed as stand-alone units or can be assembled into a J2EE application.
J2EE product: An implementation that conforms to the J2EE platform specification.
J2EE product provider: A vendor that supplies a J2EE product.
J2EE server: The runtime portion of a J2EE product. A J2EE server provides EJB or Web containers or both.
J2ME: See Java 2 Platform, Micro Edition.
J2SE: See Java 2 Platform, Standard Edition.
JAR: Java archive. A platform-independent file format that permits many files to be aggregated into one file.
Java 2 Platform, Enterprise Edition (J2EE): An environment for developing and deploying enterprise applications. The J2EE platform consists of a set of services, application programming interfaces (APIs), and protocols that provide the functionality for developing multitiered, Web-based applications.
Java 2 Platform, Micro Edition (J2ME): A highly optimized Java runtime environment targeting a wide range of consumer products, including pagers, cellular phones, screen phones, digital set-top boxes, and car navigation systems.
Java 2 Platform, Standard Edition (J2SE): The core Java technology platform.
Java API for XML Processing (JAXP): An API for processing XML documents. JAXP leverages the parser standards SAX and DOM so that you can choose to parse your data as a stream of events or to build a tree-structured representation of it. JAXP supports the XSLT standard, giving you control over the presentation of the data and enabling you to convert the data to other XML documents or to other formats, such as HTML. JAXP provides namespace support, allowing you to work with schema that might otherwise have naming conflicts.
Java API for XML Registries (JAXR): An API for accessing various kinds of XML registries.
Java API for XML-based RPC (JAX-RPC): An API for building Web services and clients that use remote procedure calls and XML.
Java IDL: A technology that provides CORBA interoperability and connectivity capabilities for the J2EE platform. These capabilities enable J2EE applications to invoke operations on remote network services using the Object Management Group IDL and IIOP.
Java Message Service (JMS): An API for invoking operations on enterprise messaging systems.
Java Naming and Directory Interface (JNDI): An API that provides naming and directory functionality.
Java Secure Socket Extension (JSSE): A set of packages that enable secure Internet communications.
Java Transaction API (JTA): An API that allows applications and J2EE servers to access transactions.
Java Transaction Service (JTS): Specifies the implementation of a transaction manager that supports JTA and implements the Java mapping of the Object Management Group Object Transaction Service 1.1 specification at the level below the API.
JavaBeans component: A Java class that can be manipulated by tools and composed into applications. A JavaBeans component must adhere to certain property and event interface conventions.
JavaMail: An API for sending and receiving email.
JavaServer Faces Technology: A framework for building server-side user interfaces for Web applications written in the Java programming language.
JavaServer Faces conversion model: A mechanism for converting between string-based markup generated by JavaServer Faces UI components and server-side Java objects.
JavaServer Faces event and listener model: A mechanism for determining how events emitted by JavaServer Faces UI components are handled. This model is based on the JavaBeans component event and listener model.
JavaServer Faces expression language: A simple expression language used by a JavaServer Faces UI component tag attributes to bind the associated component to a bean property or to bind the associated component's value to a method or an external data source, such as a bean property. Unlike JSP EL expressions, JavaServer Faces EL expressions are evaluated by the JavaServer Faces implementation rather than by the Web container.
JavaServer Faces navigation model: A mechanism for defining the sequence in which pages in a JavaServer Faces application are displayed.
JavaServer Faces UI component: A user interface control that outputs data to a client or allows a user to input data to a JavaServer Faces application.
JavaServer Faces UI component class: A JavaServer Faces class that defines the behavior and properties of a JavaServer Faces UI component.
JavaServer Faces validation model: A mechanism for validating the data a user inputs to a JavaServer Faces UI component.
JavaServer Pages (JSP): An extensible Web technology that uses static data, JSP elements, and server-side Java objects to generate dynamic content for a client. Typically the static data is HTML or XML elements, and in many cases the client is a Web browser.
JavaServer Pages Standard Tag Library (JSTL): A tag library that encapsulates core functionality common to many JSP applications. JSTL has support for common, structural tasks such as iteration and conditionals, tags for manipulating XML documents, internationalization and locale-specific formatting tags, SQL tags, and functions.
JAXR client: A client program that uses the JAXR API to access a business registry via a JAXR provider.
JAXR provider: An implementation of the JAXR API that provides access to a specific registry provider or to a class of registry providers that are based on a common specification.
JDBC: An API for database-independent connectivity between the J2EE platform and a wide range of data sources.
JMS: See Java Message Service.
JMS administered object: A preconfigured JMS object (a resource manager connection factory or a destination) created by an administrator for the use of JMS clients and placed in a JNDI namespace.
JMS application: One or more JMS clients that exchange messages.
JMS client: A Java language program that sends or receives messages.
JMS provider: A messaging system that implements the Java Message Service as well as other administrative and control functionality needed in a full-featured messaging product.
JMS session: A single-threaded context for sending and receiving JMS messages. A JMS session can be nontransacted, locally transacted, or participating in a distributed transaction.
JNDI: See Java Naming and Directory Interface.
JSP: See JavaServer Pages.
JSP action: A JSP element that can act on implicit objects and other server-side objects or can define new scripting variables. Actions follow the XML syntax for elements, with a start tag, a body, and an end tag; if the body is empty it can also use the empty tag syntax. The tag must use a prefix. There are standard and custom actions.
JSP container: A container that provides the same services as a servlet container and an engine that interprets and processes JSP pages into a servlet.
JSP container, distributed: A JSP container that can run a Web application that is tagged as distributable and is spread across multiple Java virtual machines that might be running on different hosts.
JSP custom action: A user-defined action described in a portable manner by a tag library descriptor and imported into a JSP page by a taglib directive. Custom actions are used to encapsulate recurring tasks in writing JSP pages.
JSP custom tag: A tag that references a JSP custom action.
JSP declaration: A JSP scripting element that declares methods, variables, or both in a JSP page.
JSP directive: A JSP element that gives an instruction to the JSP container and is interpreted at translation time.
JSP document: A JSP page written in XML syntax and subject to the constraints of XML documents.
JSP element: A portion of a JSP page that is recognized by a JSP translator. An element can be a directive, an action, or a scripting element.
JSP expression: A scripting element that contains a valid scripting language expression that is evaluated, converted to a String, and placed into the implicit out object.
JSP expression language: A language used to write expressions that access the properties of JavaBeans components. EL expressions can be used in static text and in any standard or custom tag attribute that can accept an expression.
JSP page: A text-based document containing static text and JSP elements that describes how to process a request to create a response. A JSP page is translated into and handles requests as a servlet.
JSP scripting element: A JSP declaration, scriptlet, or expression whose syntax is defined by the JSP specification and whose content is written according to the scripting language used in the JSP page. The JSP specification describes the syntax and semantics for the case where the language page attribute is "java".
JSP scriptlet: A JSP scripting element containing any code fragment that is valid in the scripting language used in the JSP page. The JSP specification describes what is a valid scriptlet for the case where the language page attribute is "java".
JSP standard action: An action that is defined in the JSP specification and is always available to a JSP page.
JSP tag file: A source file containing a reusable fragment of JSP code that is translated into a tag handler when a JSP page is translated into a servlet.
JSP tag handler: A Java programming language object that implements the behavior of a custom tag.
JSP tag library: A collection of custom tags described via a tag library descriptor and Java classes.
JSTL: See JavaServer Pages Standard Tag Library.
JTA: See Java Transaction API.
JTS: See Java Transaction Service.

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keystore: A file containing the keys and certificates used for authentication.

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life cycle (J2EE component): The framework events of a J2EE component's existence. Each type of component has defining events that mark its transition into states in which it has varying availability for use. For example, a servlet is created and has its init method called by its container before invocation of its service method by clients or other servlets that require its functionality. After the call of its init method, it has the data and readiness for its intended use. The servlet's destroy method is called by its container before the ending of its existence so that processing associated with winding up can be done and resources can be released. The init and destroy methods in this example are callback methods. Similar considerations apply to the life cycle of all J2EE component types: enterprise beans, Web components (servlets or JSP pages), applets, and application clients.
life cycle (JavaServer Faces): A set of phases during which a request for a page is received, a UI component tree representing the page is processed, and a response is produced. During the phases of the life cycle:

The local data of the components is updated with the values contained in the request parameters.
Events generated by the components are processed.
Validators and converters registered on the components are processed.
The components' local data is updated to back-end objects.
The response is rendered to the client while the component state of the response is saved on the server for future requests.

light-weight process|| ˆ: Solaris threads are implemented as a user-level library, using the kernel's threads of control, that are called light-weight processes (LWPs). In the Solaris environment, a process is a collection of LWPs that share memory. Each LWP has the scheduling priority of a UNIX process and shares the resources of that process. LWPs coordinate their access to the shared memory by using synchronization mechanisms such as locks. An LWP can be thought of as a virtual CPU that executes code or system calls. The threads library schedules threads on a pool of LWPs in the process, in much the same way as the kernel schedules LWPs on a pool of processors. Each LWP is independently dispatched by the kernel, performs independent system calls, incurs independent page faults, and runs in parallel on a multiprocessor system. The LWPs are scheduled by the kernel onto the available CPU resources according to their scheduling class and priority.
local subset: That part of the DTD that is defined within the current XML file.
lock|| ˆ: A mechanism for enforcing a policy for serializing access to shared data. A thread or process uses a particular lock in order to gain access to shared memory protected by that lock. The locking and unlocking of data is voluntary in the sense that only the programmer knows what must be locked. See also data race, mutual exclusion, mutex lock, semaphore lock, single-lock strategy, spin lock.
LWP|| ˆ: See light-weight process.

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managed bean creation facility: A mechanism for defining the characteristics of JavaBeans components used in a JavaServer Faces application.
MBus|| ˆ: MBus is a bus specification for a processor/memory/IO interconnect. It is licensed by SPARC International to several silicon vendors who produce interoperating CPU modules, IO interfaces and memory controllers. MBus is a circuit-switched protocol combining read requests and response on a single bus. MBus level I defines uniprocessor signals; MBus level II defines multiprocessor extensions for the write-invalidate cache coherence mechanism.
memory|| ˆ: A medium that can retain information for subsequent retrieval. The term is most frequently used for referring to a computer's internal storage that can be directly addressed by machine instructions. See also cache, distributed memory, shared memory.
message: In the Java Message Service, an asynchronous request, report, or event that is created, sent, and consumed by an enterprise application and not by a human. It contains vital information needed to coordinate enterprise applications, in the form of precisely formatted data that describes specific business actions.
message consumer: An object created by a JMS session that is used for receiving messages sent to a destination.
message-driven bean: An enterprise bean that is an asynchronous message consumer. A message-driven bean has no state for a specific client, but its instance variables can contain state across the handling of client messages, including an open database connection and an object reference to an EJB object. A client accesses a message-driven bean by sending messages to the destination for which the bean is a message listener.
message passing|| ˆ: In the distributed memory architecture, a mechanism for processes to communicate with each other. There is no shared data structure in which they deposit messages. Message passing allows a process to send data to another process and for the intended recipient to synchronize with the arrival of the data.
message producer: An object created by a JMS session that is used for sending messages to a destination.
MIMD|| ˆ: See Multiple Instruction Multiple Data, shared memory.
mixed-content model: A DTD specification that defines an element as containing a mixture of text and one more other elements. The specification must start with #PCDATA, followed by diverse elements, and must end with the "zero-or-more" asterisk symbol (*).
method-binding expression: A JavaServer Faces EL expression that refers to a method of a backing bean. This method performs either event handling, validation, or navigation processing for the UI component whose tag uses the method-binding expression.
method permission: An authorization rule that determines who is permitted to execute one or more enterprise bean methods.
mt-safe|| ˆ: In the Solaris environment, function calls inside libraries are either mt-safe or not mt-safe; mt-safe code is also called "re-entrant" code. That is, several threads can simultaneously call a given function in a module and it is up to the function code to handle this. The assumption is that data shared between threads is only accessed by module functions. If mutable global data is available to clients of a module, appropriate locks must also be made visible in the interface. Furthermore, the module function cannot be made re-entrant unless the clients are assumed to use the locks consistently and at appropriate times. See also single-lock strategy.
Multiple Instruction Multiple Data|| ˆ: System model where many processors can be simultaneously executing different instructions on different data. Furthermore, these processors operate in a largely autonomous manner as if they are separate computers. They have no central controller, and they typically do not operate in lock-step fashion. Most real world banks run this way. Tellers do not consult with one another, nor do they perform each step of every transaction at the same time. Instead, they work on their own, until a data access conflict occurs. Processing of transactions occurs without concern for timing or customer order. But customers A and B must be explicitly prevented from simultaneously accessing the joint AB account balance. MIMD relies on synchronization mechanisms called locks to coordinate access to shared resources. See also mutual exclusion, mutex lock, semaphore lock, single-lock strategy, spin lock.
multiple read single write|| ˆ: In a concurrent environment, the first process to access data for writing has exclusive access to it, making concurrent write access or simultaneous read and write access impossible. However, the data can be read by multiple readers.
multiprocessor|| ˆ: See multiprocessor system.
multiprocessor bus|| ˆ: In a shared memory multiprocessor machine each CPU and cache module are connected together via a bus that also includes memory and IO connections. The bus enforces a cache coherency protocol. See also cache, coherence, Mbus, XDBus.
multiprocessor system|| ˆ: A system in which more than one processor can be active at any given time. While the processors are actively executing separate processes, they run completely asynchronously. However, synchronization between processors is essential when they access critical system resources or critical regions of system code. See also critical region, critical resource, multithreading, uniprocessor system.
multitasking|| ˆ: In a uniprocessor system, a large number of threads appear to be running in parallel. This is accomplished by rapidly switching between threads.
multithreading ˆ: Applications that can have more than one thread or processor active at one time. Multithreaded applications can run in both uniprocessor systems and multiprocessor systems. See also bound thread, mt-safe, single-lock strategy, thread, unbound thread, uniprocessor.
mutual authentication: An authentication mechanism employed by two parties for the purpose of proving each other's identity to one another.
mutex lock|| ˆ: Synchronization variable to implement the mutual exclusion mechanism. See also condition variable, mutual exclusion.
mutual exclusion|| ˆ: In a concurrent environment, the ability of a thread to update a critical resource without accesses from competing threads. See also critical region, critical resource.

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namespace: A standard that lets you specify a unique label for the set of element names defined by a DTD. A document using that DTD can be included in any other document without having a conflict between element names. The elements defined in your DTD are then uniquely identified so that, for example, the parser can tell when an element <name> should be interpreted according to your DTD rather than using the definition for an element <name> in a different DTD.
naming context: A set of associations between unique, atomic, people-friendly identifiers and objects.
naming environment: A mechanism that allows a component to be customized without the need to access or change the component's source code. A container implements the component's naming environment and provides it to the component as a JNDI naming context. Each component names and accesses its environment entries using the java:comp/env JNDI context. The environment entries are declaratively specified in the component's deployment descriptor.
NaN ˆ: Stands for Not a Number. A symbolic entity that is encoded in floating-point format.
normalization: The process of removing redundancy by modularizing, as with subroutines, and of removing superfluous differences by reducing them to a common denominator. For example, line endings from different systems are normalized by reducing them to a single new line, and multiple whitespace characters are normalized to one space.
North American Industry Classification System (NAICS): A system for classifying business establishments based on the processes they use to produce goods or services.
notation: A mechanism for defining a data format for a non-XML document referenced as an unparsed entity. This is a holdover from SGML. A newer standard is to use MIME data types and namespaces to prevent naming conflicts.

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OASIS: Organization for the Advancement of Structured Information Standards. A consortium that drives the development, convergence, and adoption of e-business standards. Its Web site is http://www.oasis-open.org/. The DTD repository it sponsors is at http://www.XML.org.
OMG: Object Management Group. A consortium that produces and maintains computer industry specifications for interoperable enterprise applications. Its Web site is http://www.omg.org/.
one-way messaging: A method of transmitting messages without having to block until a response is received.
ORB: Object request broker. A library that enables CORBA objects to locate and communicate with one another.
OS principal: A principal native to the operating system on which the J2EE platform is executing.
OTS: Object Transaction Service. A definition of the interfaces that permit CORBA objects to participate in transactions.

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packet switching|| ˆ: In the shared memory architecture, a mechanism for caches to communicate with each other as well as with main memory. In packet switching, traffic is divided into small segments called packets that are multiplexed onto the bus. A packet carries identification that enables cache and memory hardware to determine whether the packet is destined for it or to send the packet on to its ultimate destination. Packet switching allows bus traffic to be multiplexed and unordered (not sequenced) packets to be put on the bus. The unordered packets are reassembled at the destination (cache or main memory). See also cache, shared memory.
paradigm|| ˆ: A model of the world that is used to formulate a computer solution to a problem. Paradigms provide a context in which to understand and solve a real-world problem. Because a paradigm is a model, it abstracts the details of the problem from the reality, and in doing so, makes the problem easier to solve. Like all abstractions, however, the model can be inaccurate because it only approximates the real world. See also Multiple Instruction Multiple Data, Single Instruction Multiple Data, Single Instruction Single Data, Single Program Multiple Data.
parallel processing|| ˆ: In a multiprocessor system, true parallel execution is achieved where a large number of threads or processes can be active at one time. See also concurrence, multiprocessor system, multithreading, uniprocessor.
parallelism|| ˆ: See concurrent processes, multithreading.
parameter entity: An entity that consists of DTD specifications, as distinct from a general entity. A parameter entity defined in the DTD can then be referenced at other points, thereby eliminating the need to recode the definition at each location it is used.
parsed entity: A general entity that contains XML and therefore is parsed when inserted into the XML document, as opposed to an unparsed entity.
parser: A module that reads in XML data from an input source and breaks it into chunks so that your program knows when it is working with a tag, an attribute, or element data. A nonvalidating parser ensures that the XML data is well formed but does not verify that it is valid. See also validating parser.
passivation: The process of transferring an enterprise bean from memory to secondary storage. See activation.
persistence: The protocol for transferring the state of an entity bean between its instance variables and an underlying database.
persistent field: A virtual field of an entity bean that has container-managed persistence; it is stored in a database.
pipeline|| ˆ: If the total function applied to the data can be divided into distinct processing phases, different portions of data can flow along from phase to phase; such as a compiler with phases for lexical analysis, parsing, type checking, code generation and so on. As soon as the first program or module has passed the lexical analysis phase, it can be passed on to the parsing phase while the lexical analyzer starts on the second program or module. See also array processing, vector processing.
pipelining ˆ: A hardware feature where operations are reduced to multiple stages, each of which takes (typically) one cycle to complete. The pipeline is filled when new operations can be issued each cycle. If there are no dependencies among instructions in the pipe, new results can be delivered each cycle. Chaining implies pipelining of dependent instructions. If dependent instructions cannot be chained, when the hardware does not support chaining of those particular instructions, then the pipeline stalls.
POA: Portable Object Adapter. A CORBA standard for building server-side applications that are portable across heterogeneous ORBs.
point-to-point messaging system: A messaging system built on the concept of message queues. Each message is addressed to a specific queue; clients extract messages from the queues established to hold their messages.
precision ˆ: A quantitative measure of the density of representable numbers. For example, in a binary floating point format that has a precision of 53 significant bits, there are 253 representable numbers between any two adjacent powers of two (within the range of normal numbers). Do not confuse precision with accuracy, which expresses how closely one number approximates another.
primary key: An object that uniquely identifies an entity bean within a home.
principal: The identity assigned to a user as a result of authentication.
privilege: A security attribute that does not have the property of uniqueness and that can be shared by many principals.
process|| ˆ: A unit of activity characterized by a single sequential thread of execution, a current state, and an associated set of system resources.
processing instruction: Information contained in an XML structure that is intended to be interpreted by a specific application.
programmatic security: Security decisions that are made by security-aware applications. Programmatic security is useful when declarative security alone is not sufficient to express the security model of an application.
prolog: The part of an XML document that precedes the XML data. The prolog includes the declaration and an optional DTD.
public key certificate: Used in client-certificate authentication to enable the server, and optionally the client, to authenticate each other. The public key certificate is the digital equivalent of a passport. It is issued by a trusted organization, called a certificate authority, and provides identification for the bearer.
publish/subscribe messaging system: A messaging system in which clients address messages to a specific node in a content hierarchy, called a topic. Publishers and subscribers are generally anonymous and can dynamically publish or subscribe to the content hierarchy. The system takes care of distributing the messages arriving from a node's multiple publishers to its multiple subscribers.

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query string: A component of an HTTP request URL that contains a set of parameters and values that affect the handling of the request.
queue: See point-to-point messaging system.
quiet NaN ˆ: A NaN (not a number) that propagates through almost every arithmetic operation without raising new exceptions.

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radix ˆ

The base number of any system of numbers. For example, 2 is the radix of a binary system, and 10 is the radix of the decimal system of numeration. SPARC workstations use radix-2 arithmetic; IEEE Std 754 is a radix-2 arithmetic standard.

RAR

Resource Adapter Archive. A JAR archive that contains a resource adapter module.

RDF

Resource Description Framework. A standard for defining the kind of data that an XML file contains. Such information can help ensure semantic integrity-for example-by helping to make sure that a date is treated as a date rather than simply as text.

RDF schema

A standard for specifying consistency rules that apply to the specifications contained in an RDF.

realm

See security policy domain. Also, a string, passed as part of an HTTP request during basic authentication, that defines a protection space. The protected resources on a server can be partitioned into a set of protection spaces, each with its own authentication scheme or authorization database or both.

In the J2EE server authentication service, a realm is a complete database of roles, users, and groups that identify valid users of a Web application or a set of Web applications.

reentrant entity bean

An entity bean that can handle multiple simultaneous, interleaved, or nested invocations that will not interfere with each other.

reference

See entity reference.

registry

An infrastructure that enables the building, deployment, and discovery of Web services. It is a neutral third party that facilitates dynamic and loosely coupled business-to-business (B2B) interactions.

registry provider

An implementation of a business registry that conforms to a specification for XML registries (for example, ebXML or UDDI).

relationship field

A virtual field of an entity bean having container-managed persistence; it identifies a related entity bean.

remote interface

One of two interfaces for an enterprise bean. The remote interface defines the business methods callable by a client.

remove method

Method defined in the home interface and invoked by a client to destroy an enterprise bean.

render kit

A set of renderers that render output to a particular client. The JavaServer Faces implementation provides a standard HTML render kit, which is composed of renderers that can render HMTL markup.

renderer

A Java class that can render the output for a set of JavaServer Faces UI components.

request-response messaging

A method of messaging that includes blocking until a response is received.

resource adapter

A system-level software driver that is used by an EJB container or an application client to connect to an enterprise information system. A resource adapter typically is specific to an enterprise information system. It is available as a library and is used within the address space of the server or client using it. A resource adapter plugs in to a container. The application components deployed on the container then use the client API (exposed by the adapter) or tool-generated high-level abstractions to access the underlying enterprise information system. The resource adapter and EJB container collaborate to provide the underlying mechanisms-transactions, security, and connection pooling-for connectivity to the enterprise information system.

resource adapter module

A deployable unit that contains all Java interfaces, classes, and native libraries, implementing a resource adapter along with the resource adapter deployment descriptor.

resource manager

Provides access to a set of shared resources. A resource manager participates in transactions that are externally controlled and coordinated by a transaction manager. A resource manager typically is in a different address space or on a different machine from the clients that access it. Note: An enterprise information system is referred to as a resource manager when it is mentioned in the context of resource and transaction management.

resource manager connection

An object that represents a session with a resource manager.

resource manager connection factory

An object used for creating a resource manager connection.

RMI

Remote Method Invocation. A technology that allows an object running in one Java virtual machine to invoke methods on an object running in a different Java virtual machine.

RMI-IIOP

A version of RMI implemented to use the CORBA IIOP protocol. RMI over IIOP provides interoperability with CORBA objects implemented in any language if all the remote interfaces are originally defined as RMI interfaces.

role (development)

The function performed by a party in the development and deployment phases of an application developed using J2EE technology. The roles are application component provider, application assembler, deployer, J2EE product provider, EJB container provider, EJB server provider, Web container provider, Web server provider, tool provider, and system administrator.

role mapping

The process of associating the groups or principals (or both), recognized by the container with security roles specified in the deployment descriptor. Security roles must be mapped by the deployer before a component is installed in the server.

role (security)

An abstract logical grouping of users that is defined by the application assembler. When an application is deployed, the roles are mapped to security identities, such as principals or groups, in the operational environment.

In the J2EE server authentication service, a role is an abstract name for permission to access a particular set of resources. A role can be compared to a key that can open a lock. Many people might have a copy of the key; the lock doesn't care who you are, only that you have the right key.

rollback

The point in a transaction when all updates to any resources involved in the transaction are reversed.

root

The outermost element in an XML document. The element that contains all other elements.

round ˆ

Inexact results must be rounded up or down to obtain representable values. When a result is rounded up, it is increased to the next representable value. When rounded down, it is reduced to the preceding representable value.

roundoff error ˆ

The error introduced when a real number is rounded to a machine-representable number. Most floating-point calculations incur roundoff error. For any one floating-point operation, IEEE Std 754 specifies that the result shall not incur more than one rounding error.

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SAX: See Simple API for XML.
Simple API for XML: An event-driven interface in which the parser invokes one of several methods supplied by the caller when a parsing event occurs. Events include recognizing an XML tag, finding an error, encountering a reference to an external entity, or processing a DTD specification.
schema: A database-inspired method for specifying constraints on XML documents using an XML-based language. Schemas address deficiencies in DTDs, such as the inability to put constraints on the kinds of data that can occur in a particular field. Because schemas are founded on XML, they are hierarchical. Thus it is easier to create an unambiguous specification, and it is possible to determine the scope over which a comment is meant to apply.
Secure Socket Layer (SSL): A technology that allows Web browsers and Web servers to communicate over a secured connection.
security attributes: A set of properties associated with a principal. Security attributes can be associated with a principal by an authentication protocol or by a J2EE product provider or both.
security constraint: A declarative way to annotate the intended protection of Web content. A security constraint consists of a Web resource collection, an authorization constraint, and a user data constraint.
security context: An object that encapsulates the shared state information regarding security between two entities.
security permission: A mechanism defined by J2SE, and used by the J2EE platform to express the programming restrictions imposed on application component developers.
security permission set: The minimum set of security permissions that a J2EE product provider must provide for the execution of each component type.
security policy domain: A scope over which security policies are defined and enforced by a security administrator. A security policy domain has a collection of users (or principals), uses a well-defined authentication protocol or protocols for authenticating users (or principals), and may have groups to simplify setting of security policies.
security role: See role (security).
security technology domain: A scope over which the same security mechanism is used to enforce a security policy. Multiple security policy domains can exist within a single technology domain.
security view: The set of security roles defined by the application assembler.
semaphore|| ˆ: A special-purpose data type introduced by E. W. Dijkstra that coordinates access to a particular resource or set of shared resources. A semaphore has an integer value (that cannot become negative) with two operations allowed on it. The signal (V or up) operation increases the value by one, and in general indicates that a resource has become free. The wait (P or down) operation decreases the value by one, when that can be done without the value going negative, and in general indicates that a free resource is about to start being used. See also semaphore lock.
semaphore lock|| ˆ: Synchronization mechanism for controlling access to critical resources by cooperating asynchronous threads. See also semaphore
sequential processes|| ˆ: Processes that execute in such a manner that one must finish before the next begins. See also concurrent processes, process.
server certificate: Used with the HTTPS protocol to authenticate Web applications. The certificate can be self-signed or approved by a certificate authority (CA). The HTTPS service of the Sun Java System Application Server Platform Edition 8 will not run unless a server certificate has been installed.
server principal: The OS principal that the server is executing as.
service element: A representation of the combination of one or more Connector components that share a single engine component for processing incoming requests.
service endpoint interface: A Java interface that declares the methods that a client can invoke on a Web service.
servlet: A Java program that extends the functionality of a Web server, generating dynamic content and interacting with Web applications using a request-response paradigm.
servlet container: A container that provides the network services over which requests and responses are sent, decodes requests, and formats responses. All servlet containers must support HTTP as a protocol for requests and responses but can also support additional request-response protocols, such as HTTPS.
servlet container, distributed: A servlet container that can run a Web application that is tagged as distributable and that executes across multiple Java virtual machines running on the same host or on different hosts.
servlet context: An object that contains a servlet's view of the Web application within which the servlet is running. Using the context, a servlet can log events, obtain URL references to resources, and set and store attributes that other servlets in the context can use.
servlet mapping: Defines an association between a URL pattern and a servlet. The mapping is used to map requests to servlets.
session: An object used by a servlet to track a user's interaction with a Web application across multiple HTTP requests.
session bean: An enterprise bean that is created by a client and that usually exists only for the duration of a single client-server session. A session bean performs operations, such as calculations or database access, for the client. Although a session bean can be transactional, it is not recoverable should a system crash occur. Session bean objects either can be stateless or can maintain conversational state across methods and transactions. If a session bean maintains state, then the EJB container manages this state if the object must be removed from memory. However, the session bean object itself must manage its own persistent data.
set associative cache|| ˆ: In a set associative cache, there are a fixed number of locations (at least two) where each block can be placed. A set associative cache with n locations for a block is called an n-way set associative cache. An n-way set associative cache consists of more than one set, each of which consists of n blocks. A block can be placed in any location (element) of that set. Increasing the associativity level (number of blocks in a set) increases the cache hit rate. See also cache, cache locality, false sharing, write-invalidate, write-update.
SGML: Standard Generalized Markup Language. The parent of both HTML and XML. Although HTML shares SGML's propensity for embedding presentation information in the markup, XML is a standard that allows information content to be totally separated from the mechanisms for rendering that content.
shared memory architecture|| ˆ: In a bus-connected multiprocessor system, processes or threads communicate through a global memory shared by all processors. This shared data segment is placed in the address space of the cooperating processes between their private data and stack segments. Subsequent tasks spawned by fork() copy all but the shared data segment in their address space. Shared memory requires program language extensions and library routines to support the model.
signaling NaN ˆ: A NaN (not a number) that raises the invalid operation exception whenever it appears as an operand.
significand ˆ: The component of a floating-point number that is multiplied by a signed power of the base to determine the value of the number. In a normalized number, the significand consists of a single nonzero digit to the left of the radix point and a fraction to the right.
SIMD|| ˆ: See Single Instruction Multiple Data.
Single Instruction Multiple Data|| ˆ: System model where there are many processing elements, but they are designed to execute the same instruction at the same time; that is, one program counter is used to sequence through a single copy of the program. SIMD is especially useful for solving problems that have lots of data that needs to be updated on a wholesale basis; such as numerical calculations that are regular. Many scientific and engineering applications (such as, image processing, particle simulation, and finite element methods) naturally fall into the SIMD paradigm. See also array processing, pipeline, vector processing.
Single Instruction Single Data|| ˆ: The conventional uniprocessor model, with a single processor fetching and executing a sequence of instructions that operate on the data items specified
within them. This is the original von Neumann model of the operation of a computer.
single precision ˆ: Using one computer word to represent a number.
Single Program Multiple Data|| ˆ: A form of asynchronous parallelism where simultaneous processing of different data occurs without lock-step coordination. In SPMD, processors can execute different instructions at the same time; such as, different branches of an if-then-else statement.
single-lock strategy|| ˆ: In the single-lock strategy, a thread acquires a single, application-wide mutex lock whenever any thread in the application is running and releases the lock before the thread blocks. The single-lock strategy requires cooperation from all modules and libraries in the system to synchronize on the single lock. Because only one thread can be accessing shared data at any given time, each thread has a consistent view of memory. This strategy is quite effective in a uniprocessor, provided shared memory is put into a consistent state before the lock is released and that the lock is released often enough to allow other threads to run. Furthermore, in uniprocessor systems, concurrency is diminished if the lock is not dropped during most I/O operations. The single-lock strategy cannot be applied in a multiprocessor system.
SISD|| ˆ: See Single Instruction Single Data.
snooping|| ˆ: The most popular protocol for maintaining cache coherency is called snooping. Cache controllers monitor or snoop on the bus to determine whether or not the cache contains a copy of a shared block.

For reads, multiple copies can reside in the cache of different processors, but because the processors need the most recent copy, all processors must get new values after a write. See also cache, competitive-caching, false sharing, write-invalidate, write-update.

For writes, a processor must have exclusive access to write to cache. Writes to unshared blocks do not cause bus traffic. The consequence of a write to shared data is either to invalidate all other copies or to update the shared copies with the value being written. See also cache, competitive-caching, false sharing, write-invalidate, write-update.
SOAP: Simple Object Access Protocol. A lightweight protocol intended for exchanging structured information in a decentralized, distributed environment. It defines, using XML technologies, an extensible messaging framework containing a message construct that can be exchanged over a variety of underlying protocols.
SOAP with Attachments API for Java (SAAJ): The basic package for SOAP messaging, SAAJ contains the API for creating and populating a SOAP message.
spin lock|| ˆ: Threads use a spin lock to test a lock variable over and over until some other task releases the lock. That is, the waiting thread spins on the lock until the lock is cleared. Then, the waiting thread sets the lock while inside the critical region. After work in the critical region is complete, the thread clears the spin lock so another thread can enter the critical region. The difference between a spin lock and a mutex is that an attempt to get a mutex held by someone else will block and release the LWP; a spin lock does not release the LWP. See also mutex lock.
SPMD|| ˆ: See Single Program Multiple Data.
SQL: Structured Query Language. The standardized relational database language for defining database objects and manipulating data.
SQL/J: A set of standards that includes specifications for embedding SQL statements in methods in the Java programming language and specifications for calling Java static methods as SQL stored procedures and user-defined functions. An SQL checker can detect errors in static SQL statements at program development time, rather than at execution time as with a JDBC driver.
SSL: Secure Socket Layer. A security protocol that provides privacy over the Internet. The protocol allows client-server applications to communicate in a way that cannot be eavesdropped upon or tampered with. Servers are always authenticated, and clients are optionally authenticated.
stateful session bean: A session bean with a conversational state.
stderr ˆ: Standard Error is the Unix file pointer to standard error output. This file is opened when a program is started.
stateless session bean: A session bean with no conversational state. All instances of a stateless session bean are identical.
Store 0 ˆ: Flushing the underflowed result of an arithmetic operation to zero.
subnormal number ˆ: In IEEE arithmetic, a nonzero floating point number with a biased exponent of zero. The subnormal numbers are those between zero and the smallest normal number.
system administrator: The person responsible for configuring and administering the enterprise's computers, networks, and software systems.

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tag: In XML documents, a piece of text that describes a unit of data or an element. The tag is distinguishable as markup, as opposed to data, because it is surrounded by angle brackets (< and >). To treat such markup syntax as data, you use an entity reference or a CDATA section.
tarball: see tarfile
tarfile: The tar(1) command archives and extracts files to and from a single file called a tarfile. Also known as a tarball.
template: A set of formatting instructions that apply to the nodes selected by an XPath expression.
thread|| ˆ: A flow of control within a single UNIX process address space. Solaris threads provide a light-weight form of concurrent task, allowing multiple threads of control in a common user-address space, with minimal scheduling and communication overhead. Threads share the same address space, file descriptors (when one thread opens a file, the other threads can read it), data structures, and operating system state. A thread has a program counter and a stack to keep track of local variables and return addresses. Threads interact through the use of shared data and thread synchronization operations. See also bound thread, light-weight processes, multithreading, unbound thread.
tool provider: An organization or software vendor that provides tools used for the development, packaging, and deployment of J2EE applications.
topic: See publish-subscribe messaging system.
topology|| ˆ: See interconnection network topology.
transaction: An atomic unit of work that modifies data. A transaction encloses one or more program statements, all of which either complete or roll back. Transactions enable multiple users to access the same data concurrently.
transaction attribute: A value specified in an enterprise bean's deployment descriptor that is used by the EJB container to control the transaction scope when the enterprise bean's methods are invoked. A transaction attribute can have the following values: Required, RequiresNew, Supports, NotSupported, Mandatory, or Never.
transaction isolation level: The degree to which the intermediate state of the data being modified by a transaction is visible to other concurrent transactions and data being modified by other transactions is visible to it.
transaction manager: Provides the services and management functions required to support transaction demarcation, transactional resource management, synchronization, and transaction context propagation.
two's complement ˆ: The radix complement of a binary numeral, formed by subtracting each digit from 1, then adding 1 to the least significant digit and executing any required carries. For example, the two's complement of 1101 is 0011.

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ulp ˆ: Stands for unit in last place. In binary formats, the least significant bit of the significand, bit 0, is the unit in the last place.
ulp(x) ˆ: Stands for ulp of x truncated in working format.
unbound threads|| ˆ: For Solaris threads, threads scheduled onto a pool of LWPs are called unbound threads. The threads library invokes and assigns LWPs to execute runnable threads. If the thread becomes blocked on a synchronization mechanism (such as a mutex lock) the state of the thread is saved in process memory. The threads library then assigns another thread to the LWP. See also bound thread, multithreading, thread.
underflow ˆ: A condition that occurs when the result of a floating-point arithmetic operation is so small that it cannot be represented as a normal number in the destination floating-point format with only normal roundoff.
Unicode: A standard defined by the Unicode Consortium that uses a 16-bit code page that maps digits to characters in languages around the world. Because 16 bits covers 32,768 codes, Unicode is large enough to include all the world's languages, with the exception of ideographic languages that have a different character for every concept, such as Chinese. For more information, see http://www.unicode.org/.
uniprocessor system|| ˆ: A uniprocessor system has only one processor active at any given time. This single processor can run multithreaded applications as well as the conventional single instruction single data model. See also multithreading, single instruction single data, single-lock strategy.
Universal Description, Discovery and Integration (UDDI) project: An industry initiative to create a platform-independent, open framework for describing services, discovering businesses, and integrating business services using the Internet, as well as a registry. It is being developed by a vendor consortium.
Universal Standard Products and Services Classification (UNSPSC): A schema that classifies and identifies commodities. It is used in sell-side and buy-side catalogs and as a standardized account code in analyzing expenditure.
unparsed entity: A general entity that contains something other than XML. By its nature, an unparsed entity contains binary data.
URI: Uniform resource identifier. A globally unique identifier for an abstract or physical resource. A URL is a kind of URI that specifies the retrieval protocol (http or https for Web applications) and physical location of a resource (host name and host-relative path). A URN is another type of URI.
URL: Uniform resource locator. A standard for writing a textual reference to an arbitrary piece of data in the World Wide Web. A URL looks like this: protocol://host/localinfo where protocol specifies a protocol for fetching the object (such as http or ftp), host specifies the Internet name of the targeted host, and localinfo is a string (often a file name) passed to the protocol handler on the remote host.
URL path: The part of a URL passed by an HTTP request to invoke a servlet. A URL path consists of the context path + servlet path + path info, where

Context path is the path prefix associated with a servlet context of which the servlet is a part. If this context is the default context rooted at the base of the Web server's URL namespace, the path prefix will be an empty string. Otherwise, the path prefix starts with a / character but does not end with a / character.
Servlet path is the path section that directly corresponds to the mapping that activated this request. This path starts with a / character.
Path info is the part of the request path that is not part of the context path or the servlet path.

URN: Uniform resource name. A unique identifier that identifies an entity but doesn't tell where it is located. A system can use a URN to look up an entity locally before trying to find it on the Web. It also allows the Web location to change, while still allowing the entity to be found.
user data constraint: Indicates how data between a client and a Web container should be protected. The protection can be the prevention of tampering with the data or prevention of eavesdropping on the data.
user (security): An individual (or application program) identity that has been authenticated. A user can have a set of roles associated with that identity, which entitles the user to access all resources protected by those roles.

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valid: A valid XML document, in addition to being well formed, conforms to all the constraints imposed by a DTD. It does not contain any tags that are not permitted by the DTD, and the order of the tags conforms to the DTD's specifications.
validating parser: A parser that ensures that an XML document is valid in addition to being well formed. See also parser.
value-binding expression: A JavaServer Faces EL expression that refers to a property of a backing bean. A component tag uses this expression to bind the associated component's value or the component instance to the bean property. If the component tag refers to the property via its value attribute, then the component's value is bound to the property. If the component tag refers to the property via its binding attribute then the component itself is bound to the property.
vector processing|| ˆ: Processing of sequences of data in a uniform manner, a common occurrence in manipulation of matrices (whose elements are vectors) or other arrays of data. This orderly progression of data can capitalize on the use of pipeline processing. See also array processing, pipeline.
virtual host: Multiple hosts plus domain names mapped to a single IP address.

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W3C: World Wide Web Consortium. The international body that governs Internet standards. Its Web site is http://www.w3.org/.
WAR file: Web application archive file. A JAR archive that contains a Web module.
warning: A SAX parser warning is generated when the document's DTD contains duplicate definitions and in similar situations that are not necessarily an error but which the document author might like to know about, because they could be. See also fatal error, error.
Web application: An application written for the Internet, including those built with Java technologies such as JavaServer Pages and servlets, as well as those built with non-Java technologies such as CGI and Perl.
Web application, distributable: A Web application that uses J2EE technology written so that it can be deployed in a Web container distributed across multiple Java virtual machines running on the same host or different hosts. The deployment descriptor for such an application uses the distributable element.
Web component: A component that provides services in response to requests; either a servlet or a JSP page.
Web container: A container that implements the Web component contract of the J2EE architecture. This contract specifies a runtime environment for Web components that includes security, concurrency, life-cycle management, transaction, deployment, and other services. A Web container provides the same services as a JSP container as well as a federated view of the J2EE platform APIs. A Web container is provided by a Web or J2EE server.
Web container, distributed: A Web container that can run a Web application that is tagged as distributable and that executes across multiple Java virtual machines running on the same host or on different hosts.
Web container provider: A vendor that supplies a Web container.
Web module: A deployable unit that consists of one or more Web components, other resources, and a Web application deployment descriptor contained in a hierarchy of directories and files in a standard Web application format.
Web resource: A static or dynamic object contained in a Web application that can be referenced by a URL.
Web resource collection: A list of URL patterns and HTTP methods that describe a set of Web resources to be protected.
Web server: Software that provides services to access the Internet, an intranet, or an extranet. A Web server hosts Web sites, provides support for HTTP and other protocols, and executes server-side programs (such as CGI scripts or servlets) that perform certain functions. In the J2EE architecture, a Web server provides services to a Web container. For example, a Web container typically relies on a Web server to provide HTTP message handling. The J2EE architecture assumes that a Web container is hosted by a Web server from the same vendor, so it does not specify the contract between these two entities. A Web server can host one or more Web containers.
Web server provider: A vendor that supplies a Web server.
Web service: An application that exists in a distributed environment, such as the Internet. A Web service accepts a request, performs its function based on the request, and returns a response. The request and the response can be part of the same operation, or they can occur separately, in which case the consumer does not need to wait for a response. Both the request and the response usually take the form of XML, a portable data-interchange format, and are delivered over a wire protocol, such as HTTP.
well-formed: An XML document that is syntactically correct. It does not have any angle brackets that are not part of tags, all tags have an ending tag or are themselves self-ending, and all tags are fully nested. Knowing that a document is well formed makes it possible to process it. However, a well-formed document may not be valid. To determine that, you need a validating parser and a DTD.
word ˆ: An ordered set of characters that are stored, addressed, transmitted and operated on as a single entity within a given computer. In the context of SPARC workstations, a word is 32 bits.
wrapped number ˆ: In IEEE arithmetic, a number created from a value that otherwise overflows or underflows by adding a fixed offset to its exponent to position the wrapped value in the normal number range. Wrapped results are not currently produced on SPARC workstations.
write-back|| ˆ: Write policy for maintaining coherency between cache and main memory. Write-back (also called copy back or store in) writes only to the block in local cache. Writes occur at the speed of cache memory. The modified cache block is written to main memory only when the corresponding memory address is referenced by another processor. The processor can write within a cache block multiple times and writes it to main memory only when referenced. Because every write does not go to memory, write-back reduces demands on bus bandwidth. See also cache, coherence, write-through.
write-invalidate|| ˆ: Maintains cache coherence by reading from local caches until a write occurs. To change the value of a variable the writing processor first invalidates all copies in other caches. The writing processor is then free to update its local copy until another processor asks for the variable. The writing processor issues an invalidation signal over the bus and all caches check to see if they have a copy; if so, they must invalidate the block containing the word. This scheme allows multiple readers, but only a single writer. Write-invalidate use the bus only on the first write to invalidate the other copies; subsequent local writes do not result in bus traffic, thus reducing demands on bus bandwidth. See also cache, cache locality, coherence, false sharing, write-update.
write-through|| ˆ: Write policy for maintaining coherency between cache and main memory. Write-through (also called store through) writes to main memory as well as to the block in local cache. Write-through has the advantage that main memory has the most current copy of the data. See also cache, coherence, write-back.
write-update|| ˆ: Write-update, also known as write-broadcast, maintains cache coherence by immediately updating all copies of a shared variable in all caches. This is a form of write-through because all writes go over the bus to update copies of shared data. Write-update has the advantage of making new values appear in cache sooner, which can reduce latency. See also cache, cache locality, coherence, false sharing, write-invalidate.

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Xalan: An interpreting version of XSLT.
XDBus|| ˆ: The XDBus specification uses low-impedance GTL (Gunning Transceiver Logic) transceiver signalling to drive longer backplanes at higher clock rates. XDBus supports a large number of CPUs with multiple interleaved memory banks for increased throughput. XDBus uses a packet switched protocol with split requests and responses for more efficient bus utilization. XDBus also defines an interleaving scheme so that one, two or four separate bus data paths can be used as a single backplane for increased throughput. XDBus supports write-invalidate, write-update and competitive-caching coherency schemes, and has several congestion control mechanisms. See also cache, coherence, competitive-caching, write-invalidate, write-update.
XHTML: An XML look-alike for HTML defined by one of several XHTML DTDs. To use XHTML for everything would of course defeat the purpose of XML, because the idea of XML is to identify information content, and not just to tell how to display it. You can reference it in a DTD, which allows you to say, for example, that the text in an element can contain <em> and <b> tags rather than being limited to plain text.
XLink: The part of the XLL specification that is concerned with specifying links between documents.
XLL: The XML Link Language specification, consisting of XLink and XPointer.
XML: Extensible Markup Language. A markup language that allows you to define the tags (markup) needed to identify the content, data, and text in XML documents. It differs from HTML, the markup language most often used to present information on the Internet. HTML has fixed tags that deal mainly with style or presentation. An XML document must undergo a transformation into a language with style tags under the control of a style sheet before it can be presented by a browser or other presentation mechanism. Two types of style sheets used with XML are CSS and XSL. Typically, XML is transformed into HTML for presentation. Although tags can be defined as needed in the generation of an XML document, a document type definition (DTD) can be used to define the elements allowed in a particular type of document. A document can be compared by using the rules in the DTD to determine its validity and to locate particular elements in the document. A Web services application's J2EE deployment descriptors are expressed in XML with schemas defining allowed elements. Programs for processing XML documents use SAX or DOM APIs.
XML registry: See registry.
XML Schema: The W3C specification for defining the structure, content, and semantics of XML documents.
XPath: An addressing mechanism for identifying the parts of an XML document.
XPointer: The part of the XLL specification that is concerned with identifying sections of documents so that they can be referenced in links or included in other documents.
XSL: Extensible Stylesheet Language. A standard that lets you do the following:

Specify an addressing mechanism, so that you can identify the parts of an XML document that a transformation applies to (XPath).
Specify tag conversions, so that you can convert XML data into different formats (XSLT).
Specify display characteristics, such page sizes, margins, and font heights and widths, as well as the flow objects on each page. Information fills in one area of a page and then automatically flows to the next object when that area fills up. That allows you to wrap text around pictures, for example, or to continue a newsletter article on a different page (XSL-FO).

XSL-FO: A subcomponent of XSL used for describing font sizes, page layouts, and how information flows from one page to another.
XSLT: XSL Transformations. An XML document that controls the transformation of an XML document into another XML document or HTML. The target document often has presentation-related tags dictating how it will be rendered by a browser or other presentation mechanism. XSLT was formerly a part of XSL, which also included a tag language of style flow objects.
XSLTC: A compiling version of XSLT.

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