Issue 12943: OCL 2.0:  CollectionType constraint for invalid elements is incorrect (ocl2-rtf)
Source: Zeligsoft, Inc. (Mr. Christian W. Damus, nobody)
Nature: Uncategorized Issue
Severity: 
Summary: The second constraint on CollectionType in Section 8.2.2 does not make  
sense.  The instances of CollectionType are not collections, but the  
types of collections.  Thus, a collection type does not have elements  
to be iterated.  This constraint should be struck from Section 8.2.2:


[1] A collection cannot contain OclInvalid values.
        context CollectionType
        inv: self->forAll(not oclIsInvalid())


and replaced by a new invariant constraint in Section 11.7.1  
“Collection” (which currently has no well-formedness rules):


[1] A collection cannot contain OclInvalid values.
        context Collection
        inv: self->forAll(not oclIsInvalid())


Resolution: As OCL does not permit the invalid value in a collection (as opposed to the null value), it should be made explicit that the evaluation of collection literals containing invalid results in invalid.  The CollectionType constraint in Section 8.2.2 attempts to express this, but is incorrect because it is defined on the wrong meta-level (on CollectionType instead of Collection).
Revised Text: Strike the second constraint on CollectionType in Section 8.2.2 “Well-formedness Rules for the Types Package”

[1] A collection cannot contain OclInvalid values. 
	context CollectionType 
	inv: self->forAll(not oclIsInvalid())

Add an invariant constraint to Section 11.7.1 “Collection”

[1] A collection cannot contain OclInvalid values.
	context Collection
	inv: self->forAll(not oclIsInvalid())


Actions taken:
October 9, 2008: received issue
October 16, 2009: closed issue
Discussion: 

End of Annotations:=====

m: "Christian W. Damus" <cdamus@zeligsoft.com>
To: issues@omg.org
Subject: OCL 2.0:  CollectionType constraint for invalid elements is incorrect
Date: Thu, 9 Oct 2008 12:49:27 -0400
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re:  OCL 2.0 formal/06-05-01


Section 8.2.2 .Well-formedness Rules for the Types Package.


The second constraint on CollectionType in Section 8.2.2 does not make  
sense.  The instances of CollectionType are not collections, but the  
types of collections.  Thus, a collection type does not have elements  
to be iterated.  This constraint should be struck from Section 8.2.2:


[1] A collection cannot contain OclInvalid values.
        context CollectionType
        inv: self->forAll(not oclIsInvalid())


and replaced by a new invariant constraint in Section 11.7.1  
.Collection. (which currently has no well-formedness rules):


[1] A collection cannot contain OclInvalid values.
        context Collection
        inv: self->forAll(not oclIsInvalid())


Thanks,


Christian


--
Christian W. Damus
Senior Software Developer, Zeligsoft Inc.
Component Lead, Eclipse MDT OCL and EMF-QTV
E-mail: cdamus@zeligsoft.com