Issue 15836: OCL 2.3 Incomplete CollectionRange well-formedness rules (ocl2-rtf)
Source: Model Driven Solutions (Dr. Edward Willink, ed(at)willink.me.uk)
Nature: Uncategorized Issue
Severity: 
Summary: The descriptions of CollectionRange are generally vague leaving the end inclusivities unclear.


It is only the CollectionRangeEval::getRange that provides a solid definition of well-formedness
for e.g. Sequence{1..1} as equal to Sequence{1}.


Unfortunately the specification is undecided about Sequence{2..1} since the CollectionRangeEval::getRange
recursion never terminates.


Rather than impose a well-formedness constraint that Sequence{2..1} is invalid, perhaps it should be
made useful instead, by defining .. as operating in the direction of the last wrt the first so
Sequence{2..1} = Sequence{2,1} and Set{1..2} = Set{2..1} = Set{1,2}.


Resolution: The generalization to allow down-counts can lead to nasty surprises for e.g. Sequence{1..x->size()} when x is empty. So just make it clear that Sequence{2..1} is invalid
Revised Text: 8.4 CollectionRange replace
A CollectionRange represents a range of integers.
by
A CollectionRange represents a range of integers from a first integer up to and including a last integer.
In 8.4.2 CollectionRange add
The last value follows the first value.
inv IncreasingRange: first <= last
Actions taken:
November 18, 2010: received issue
December 23, 2013: closed issue
Discussion: 


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Date: Thu, 18 Nov 2010 09:43:48 +0000
From: Ed Willink <ed@willink.me.uk>
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To: issues@omg.org
Subject: OCL 2.3 Incomplete CollectionRange well-formedness rules


Hi


The descriptions of CollectionRange are generally vague leaving the end inclusivities unclear.


It is only the CollectionRangeEval::getRange that provides a solid definition of well-formedness
for e.g. Sequence{1..1} as equal to Sequence{1}.


Unfortunately the specification is undecided about Sequence{2..1} since the CollectionRangeEval::getRange
recursion never terminates.


Rather than impose a well-formedness constraint that Sequence{2..1} is invalid, perhaps it should be
made useful instead, by defining .. as operating in the direction of the last wrt the first so
Sequence{2..1} = Sequence{2,1} and Set{1..2} = Set{2..1} = Set{1,2}.


    Regards


        Ed Willink