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By Richard Marejka, December 2004
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Question
What is the correct form of a MIDlet suite version number?
Answer
In testing a MIDlet suite recently some inexplicable errors occurred.
Sometimes the MIDlet suite would install and run successfully, sometimes it
would fail to install.
The only clear pattern was that failures were more likely on more recent
devices.
The failures were not specific to one manufacturer or to one version of the
profile, MIDP 1.0 or MIDP 2.0.
After some review, conjecture, and further testing the failure was traced to the
value of the
MIDlet-Version attribute.
When the original value ".8" was changed to
"0.8",
the suite installed and ran fine on all devices tested.
This experience led to a more detailed investigation into the question:
What is a valid version number? The MIDP 1.0 specification (on page 45) and MIDP
2.0 (on page 434)
provide the same definition of version number. To quote from
the MIDP 2.0 document:
Version numbers have the format Major.Minor[.Micro] (X.X[.X]), where the Micro
portion MAY be omitted.
(If the .Micro portion is not omitted then it defaults to zero.)
In addition, each portion of the version number is allowed a maximum of two
decimal digits (i.e. 0-99).
What's missing is an explicit statement of the minimum length
of each portion.
The note in parentheses "(i.e. 0-99)," is used to support the
statement of maximum length.
So what have we learned?
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The correct syntax of a
MIDlet-Version, expressed in
yacc grammar, is:
Version : Major '.' Minor
| Major '.' Minor '.' Micro
;
Major : number ;
Minor : number ;
Micro : number ;
number : [0-9]
| [0-9][0-9]
;
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That is, a version number is two one- or two-digit numbers separated by a
period, or three one- or two-digit numbers separated by periods.
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Natural language is sometimes difficult to parse.
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Unspecified items are just that: unspecified, and subject to
implementation-specific interpretation.
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