Issue 15218: OCL 2.2 UML-alignment of redefinition (ocl2-rtf)
Source: Model Driven Solutions (Dr. Edward Willink, ed(at)willink.me.uk)
Nature: Uncategorized Issue
Severity: 
Summary: At the end of Section 7.4.6 OCL 2.2 says


"For example, if class Employee redefines the age() : Integer operation of
the Person class, a constraint may access the
Person definition as in
context Employee
inv: self.age() <= self.Person::age()
For clarity, the qualified form may only be used with an explicit source
expression."


and in Section 7.5.8:


"Whenever properties are redefined within a type, the property of the
supertypes can be accessed using the oclAsType()
operation. Whenever we have a class B as a subtype of class A, and a
property p1 of both A and B, we can write:"


a clarifying example follows that is actually a disambiguation not a
redefinition.


In UML redefinition replaces an old definition with something else, which is
not what the above
excerpts imply.


In the case of redefining "Person::age() : Integer". If the redefinition is
"Employee::age() : UnlimitedNatural"
the redefinition is compatible (valid UML), so perhaps self.age() being
UnlimitedNatural and self.Person::age()
being Integer just might be useful. But allowing them to invoke different
operation bodies seems to violate
UML.


Suggest that use of a path qualification may select an occluded definition
signature for static analysis,
but may not use a redefined value or body.


[This then avoids a need for the AST to persist the distinction between X::y
as an explicit feature for
static resolution or as an implicit feature for dynamic resolution. All
features in the AST are identified by
static analysis and evaluated by dynamic resolution.]

Resolution: 
Revised Text: 
Actions taken:
April 22, 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 UML-alignment of redefinition
Date: Thu, 22 Apr 2010 14:24:18 +0100
X-Mailer: Internet Mail Service (5.5.2657.72)


Hi


[Juergen: Please use: "Issue xyzzy: OCL 2.2 - UML-alignment of redefinition"
rather than just "Issue xyzzy - OCL 2.2 Issue" as the moderated email
title.]


At the end of Section 7.4.6 OCL 2.2 says


"For example, if class Employee redefines the age() : Integer operation of
the Person class, a constraint may access the
Person definition as in
context Employee
inv: self.age() <= self.Person::age()
For clarity, the qualified form may only be used with an explicit source
expression."


and in Section 7.5.8:


"Whenever properties are redefined within a type, the property of the
supertypes can be accessed using the oclAsType()
operation. Whenever we have a class B as a subtype of class A, and a
property p1 of both A and B, we can write:"


a clarifying example follows that is actually a disambiguation not a
redefinition.


In UML redefinition replaces an old definition with something else, which is
not what the above
excerpts imply.


In the case of redefining "Person::age() : Integer". If the redefinition is
"Employee::age() : UnlimitedNatural"
the redefinition is compatible (valid UML), so perhaps self.age() being
UnlimitedNatural and self.Person::age()
being Integer just might be useful. But allowing them to invoke different
operation bodies seems to violate
UML.


Suggest that use of a path qualification may select an occluded definition
signature for static analysis,
but may not use a redefined value or body.


[This then avoids a need for the AST to persist the distinction between X::y
as an explicit feature for
static resolution or as an implicit feature for dynamic resolution. All
features in the AST are identified by
static analysis and evaluated by dynamic resolution.]


        Regards
                        
                Ed Willink


****************************************************************************
Please consider the environment before printing this email.
Thales Research and Technology (UK) Limited DISCLAIMER:  The information
contained in this e-mail is confidential.  It may also be legally
privileged.  It is intended only for the stated addressee(s) and access to
it by any other person is unauthorised.  If you are not an addressee, you
must not disclose, copy, circulate or in any other way use or rely on the
information contained herein.  Such unauthorised use may be unlawful.  We
may monitor all e-mail communications through our networks.  If you have
received this e-mail in error, please inform us immediately on +44 (0)1293
575987 and delete it and all copies from your system.  We accept no
responsibility for changes to any e-mail which occur after it has been sent.
Attachments to this e-mail may contain software viruses which could damage
your system.  We therefore recommend you virus-check all attachments before
opening.  The registered office of Thales Research and Technology (UK)
Limited is at: 2 Dashwood Lang Road, The Bourne Business Park, Addlestone,
Weybridge, Surrey KT15 2NX.  Registered in England No. 774298.
****************************************************************************