Issue 15258: OCL 2.2 OclMessage types are not statically derivable (ocl2-rtf)
Source: Model Driven Solutions (Dr. Edward Willink, ed(at)willink.me.uk)
Nature: Uncategorized Issue
Severity: 
Summary: The intro to Section 8.2 states:


"OCL is a typed language. Each expression has a type that is either
explicitly declared or can be statically derived."


However OclMessage lacks type parameterisation and so the 7.7.2 example


context Subject::hasChanged()
post: let messages : Sequence(OclMessage) = observer^^update(? : Integer, ?
: Integer) in
        messages->notEmpty() and
        messages->exists( m | m.i > 0 and m.j >= m.i )


only works if the type analysis proceeds beyond "messages :
Sequence(OclMessage)" to
discover the initialiser with formal signature "Observer::update(i :
Integer, j : Integer)".


This will not in general be possible and so expressions such as "m.i > 0"
cannot be
statically checked, and cannot be dynamically expressed. Indeed since m is
an OclMessage,
"m.i" is not well-formed.


Suggest that OclMessage is redefined as:


OclMessage<OclOperation> or OclMessage<OclSignal>


requiring the type to be determinate or discovered by oclAsType.


Resolution: 
Revised Text: 
Actions taken:
May 18, 2010: received issue
Discussion: 

End of Annotations:=====

m: "Willink, Ed" <Ed.Willink@thalesgroup.com>
To: "'issues@omg.org'" <issues@omg.org>
Subject: OCL 2.2 OclMessage types are not statically derivable.
Date: Tue, 18 May 2010 17:46:32 +0100
X-Mailer: Internet Mail Service (5.5.2657.72)


Hi


The intro to Section 8.2 states:


"OCL is a typed language. Each expression has a type that is either
explicitly declared or can be statically derived."


However OclMessage lacks type parameterisation and so the 7.7.2 example


context Subject::hasChanged()
post: let messages : Sequence(OclMessage) = observer^^update(? : Integer, ?
: Integer) in
        messages->notEmpty() and
        messages->exists( m | m.i > 0 and m.j >= m.i )


only works if the type analysis proceeds beyond "messages :
Sequence(OclMessage)" to
discover the initialiser with formal signature "Observer::update(i :
Integer, j : Integer)".


This will not in general be possible and so expressions such as "m.i > 0"
cannot be
statically checked, and cannot be dynamically expressed. Indeed since m is
an OclMessage,
"m.i" is not well-formed.


Suggest that OclMessage is redefined as:


OclMessage<OclOperation> or OclMessage<OclSignal>


requiring the type to be determinate or discovered by oclAsType.


        Regards
                        
                Ed Willink


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