Issue 16161: OCL 2.3 7.5.3 Missing Association End name problems (ocl2-rtf)
Source: Model Driven Solutions (Dr. Edward Willink, ed(at)willink.me.uk)
Nature: Uncategorized Issue
Severity: 
Summary: The 'clarified' text in OCL 2.3 for missing association ends, is still unclear.


Problem 1: if multiple association ends acquire the same name, what happens? Suggest: they all acquire the same name and the resulting lookup up finds multiple names which should be diagnosed as an ambiguity and consequently a semantic error.


Problem 2: if a missing association end is recursive, a class acquires a property with the same name as the class. Consequently invocation of e.g X.allInstances() for class X may encounter an ambiguity while resolving X. Is it self.X or global X? Suggest: auto-generated missing names may only be invoked via a navigation operator.


Problem 3: does a derived association end get a resolution for a missing name? if OCL is used to define a number of helper properties that all return the same type, then provision of the  missing 'opposites' results in unhelpful clutter at best. Suggest: missing names are not provided for derived association ends.


Resolution: 
Revised Text: 
Actions taken:
April 26, 2011: received issue
Discussion: 

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Date: Tue, 26 Apr 2011 22:00:35 +0100
From: Ed Willink <ed@willink.me.uk>
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To: "ocl2-rtf@omg.org" <ocl2-rtf@omg.org>
Subject: OCL 2.3 7.5.3 Missing Association End name problems


Hi


The 'clarified' text in OCL 2.3 for missing association ends, is still unclear.


Problem 1: if multiple association ends acquire the same name, what happens? Suggest: they all acquire the same name and the resulting lookup up finds multiple names which should be diagnosed as an ambiguity and consequently a semantic error.


Problem 2: if a missing association end is recursive, a class acquires a property with the same name as the class. Consequently invocation of e.g X.allInstances() for class X may encounter an ambiguity while resolving X. Is it self.X or global X? Suggest: auto-generated missing names may only be invoked via a navigation operator.


Problem 3: does a derived association end get a resolution for a missing name? if OCL is used to define a number of helper properties that all return the same type, then provision of the  missing 'opposites' results in unhelpful clutter at best. Suggest: missing names are not provided for derived association ends.


    Regards


        Ed Willink