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Subject: RE: [wsdm] On ambivalent associations






+1

Tom Maguire



                                                                           
             "Andrea                                                       
             Westerinen"                                                   
             <andreaw@cisco.co                                          To 
             m>                        "'Sedukhin, Igor S'"                
                                       <Igor.Sedukhin@ca.com>,             
             08/06/2004 02:25          <wsdm@lists.oasis-open.org>         
             PM                                                         cc 
                                                                           
                                                                   Subject 
                                       RE: [wsdm] On ambivalent            
                                       associations                        
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




The main issue with directionality is that the model semantics do not map
easily to it when a direction does not exist.  By using the words, source
and target, in the relationship definition, you have explaining to do when
they don't apply.  I would prefer to see something like Role1, Role2,
Role3, ... (assuming more than binary relationships :-) that supports all
the model semantics cleanly, rather than saying "I know that source and
target don't apply in this case, but I had to ignore that in order to fit
into the WSDM definition."  This makes the current solution wrong, IMHO.

Use of terms such as Role1, Role2, Role3 is more inline with base UML
definitions of relationships as well.  Directionality and binary
relationships are not mandated by UML.

Andrea
 -----Original Message-----
 From: Sedukhin, Igor S [mailto:Igor.Sedukhin@ca.com]
 Sent: Thursday, August 05, 2004 3:51 PM
 To: wsdm@lists.oasis-open.org
 Subject: [wsdm] On ambivalent associations



 We had this discussion today about relationships/associations being
 directional or not. I'm still trying to understand the reasoning behind
 this. One may equivalently say


 #1 A and B are friends


 #2 A is a friend of B and B is a friend of A


 I don't understand why #1 is so important.


 Handling/modeling #1 gets very intricate when there are more than two
 participants. "A and B and C are friends". Saying that this has to be
 represented as "A and B are friends" + "A and C are friends" + "B and C
 are friends" breaks the pattern here. This will be hard to compute.


 At the same time saying that "A is a friend of B" + "A is a friend of C" +
 "B is a friend of A" + "B is a friend of C" + "C is a friend of A" + "C is
 a friend of B" does not break the pattern that was already itroduced. This
 is easy to compute.


 The difference is 2x. That is not a significant difference.


 -- Igor Sedukhin .. (igor.sedukhin@ca.com)
 -- (631) 342-4325 .. 1 CA Plaza, Islandia, NY 11788





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