Issue 7825: UML 2 Superstructure -Incompatible use of term link (uml2-superstructure-ftf)
Source: The MathWorks (Mr. Alan Moore, alan.moore(at)mathworks.co.uk)
Nature: Uncategorized Issue
Severity: 
Summary: The Semantics of Association says:


"An association declares that there can be links between instances of the
associated types. A link is a tuple with one value for
each end of the assocaition, where each value is an instance of the type of
the end."


but in Semantics of Connector the spec states:


"Specifies a link that enables communication between two or more instances.
This link may be an instance of an association, or
it may represent the possibility of the instances being able to communicate
because their identities are known by virtue of
being passed in as parameters, held in variables or slots, or because the
communicating instances are the same instance."


The small issue is that link is used in incompatible ways which is
confusing. The bigger issue is that Connectors may be typed by Associations
and even if there is no actual type, one is "inferred". I would have thought
that an instance of a Connector (a link) typed by an Association would have
to be an Association Instance; one possible interpretation of this is that
an instance of a Connector is only an Association Instance if it has a
"non-inferred" type, although the value of "inferring" a type seems dubious
if that is the case. The spec should clarify the situation.
Resolution: 
Revised Text: 
Actions taken:
September 30, 2004: received issue
Discussion: 

End of Annotations:=====

m: "Moore, Alan" <Alan.Moore@artisansw.com> 
To: issues@omg.org 
Subject: UML 2 Superstructure -Incompatible use of term link 
Date: Thu, 30 Sep 2004 12:32:13 +0100 
X-Mailer: Internet Mail Service (5.5.2657.72) 


Two issues really:


The Semantics of Association says:


"An association declares that there can be links between instances of the
associated types. A link is a tuple with one value for
each end of the assocaition, where each value is an instance of the type of
the end."


but in Semantics of Connector the spec states:


"Specifies a link that enables communication between two or more instances.
This link may be an instance of an association, or
it may represent the possibility of the instances being able to communicate
because their identities are known by virtue of
being passed in as parameters, held in variables or slots, or because the
communicating instances are the same instance."


The small issue is that link is used in incompatible ways which is
confusing. The bigger issue is that Connectors may be typed by Associations
and even if there is no actual type, one is "inferred". I would have thought
that an instance of a Connector (a link) typed by an Association would have
to be an Association Instance; one possible interpretation of this is that
an instance of a Connector is only an Association Instance if it has a
"non-inferred" type, although the value of "inferring" a type seems dubious
if that is the case. The spec should clarify the situation.