RE: [Fwd: Re: asking about OCL]



RE: [Fwd: Re: asking about OCL]

From: Waldin, Earl <Earl.Waldin_at_paranor.ch>
Date: Tue, 16 May 2006 15:16:46 +0200
Message-ID: <1DE41A26EA92CA4FB831A9449AB0841E5DBF1D@srv-par2.paranor.ch>
Hi
 
While we are on the issue of notation for class properties/operations
(i.e. static properties/operations), may I point out that OCL 2.0  did
change from using the UML 1.4 '.' notation to the '::'  notation! One
may not have noticed this because Chapter 7 of the specification still
uses the old syntax. However, Chapter 7 is only informative and not
normative. Chapter 9, which defines the concrete syntax and which I
assume is normative, uses '::'. I am referring to the OCL version in the
current finalization task report (ptc/2005-06-06), which, barring any
catastrophe, will become the formal version. So the expected formal
version will not be consistent in this point. This has been  brought to
the attention of the OMG in "Issue 8937: Notation for accessing class
operations is inconsistent (ocl2-rtf)" which you can find at
 
  http://www.omg.org/issues/ocl2-rtf.open.html#Issue8937
 
Now, what we think it should be is a different issue!
 
    -Earl Waldin

-----Original Message-----
From: puml-list-request@cs.york.ac.uk
[mailto:puml-list-request@cs.york.ac.uk] On Behalf Of Anneke Kleppe
Sent: Tuesday, 16 May, 2006 13:49
To: puml-list@cs.york.ac.uk
Subject: [Fwd: Re: asking about OCL]


The predefined operation allInstances is an operation that effectively
works on a class, not on an instance. It does not make sense to ask for
the set of all instances from a single instance, instead you should ask
its class. This has not been addressed in the OCL specification
properly. There is a bit of cryptic text that says: "Returns all
instances of self. Type T is equal to self." In my opinion, the
operation allInstances should have been defined as an instance of class
Feature (UML Superstructure, section 7.3.10) with attribute 'isStatic'
set to true. 

In OCL all static features, attributes or operations, are referenced
using the double colon notation. Therefore, in my opinion, the correct
notation would be the one that Steffen mentioned: 
A::allInstances(). Unfortunately, all examples in the OCL spec. use the
single dot notation, but they do use 'CLASSNAME.allInstances()', not
self.allInstances(). As I said, the latter expression does  not make any
sense at all. In fact, in our book and in the Octopus tool, the double
colon notation is the only one that is regarded correct. :-) 

I hope this helps to clear things up.
Anneke Kleppe

Achim D. Brucker wrote: 

"Prof. Dr. Peter H. Schmitt"  <mailto:pschmitt@ira.uka.de>
<pschmitt@ira.uka.de> schrieb:

  

That is strange. I would have thougth Steffen Zschaler's comment
correct.

Is there a definite way to settle disputes of this kind?



    



in the OCL 2.0 standard, "allInstances" is defined as being an

operation of class OclAny (e.g. see chapter 11 of the standard)

and thus its use should be similar to other operations defined

within OclAny, e.g. "_=_" or oclIsNew(). Therefore, on any 

instance variable, i.e., self, one can write 

"self.allInstances()".  And by the way, the Dresden OCL Parser

also uses this as concrete syntax :-). 



In the old OCL 1.1 standard,  "allInstances()" is declared

as operation of type OclType. This leads just to another concrete

syntax:

   context Person:

   inv: Person.allInstances->size() >1



The notion "Person::allInstances" emerges often, but I have no idea

from where it comes, albeit I have often used it myself :-)



Achim

  
Received on Tue 16 May 2006 - 14:16:49 BST