RE: [discussion@2uworks.org] RE: [wg@2uworks.org] 3C + 2U = xP?



Date view Thread view Subject view Author view Attachment view

From: Joaquin Miller (miller@joaquin.net)
Date: Sat 07 Sep 2002 - 21:19:12 BST


That does help, Tony, very much so.  Thanks.

I had not realized that 'to denote' was also used to mean 'to be the 
interpretation of.'  I suppose that's because of my distinction between the 
range of the interpretation function of formal semantics and the system 
that the model represents; and because i took 'to denote' in its ordinary 
dictionary meaning (e.g. Cambridge Dictionary of Philosophy).  As a result 
of that distinction and that meaning, i would expect 'to denote' to be used 
with respect to the relation of a model element to what that element 
represents, not the relation of that element to something in an 
interpretation (model) of that model (theory).  So i had it all backwards.

Probably best to avoid the jargon of the formal semantics trade in the 2U 
documents.  That's not your problem, or puml's.  I'll suggest it to 2U.

It is reassuring to see we share the idea that there are three things, 
model (theory), system, and interpretation (model).  And at least two 
essential relations, representation and interpretation (or, as used in the 
text, denotation).

Here is where we part company:

>-- well, the meaning of the concepts-as-UML-elements is given in the 
>semantic domain;  the meaning of the real world/system is more tricky!

i would say the meaning of the model elements is found in the system.
and that the system has no meaning.
(Sure, some things do have meaning.  If statues of the leader are erected 
in the squares, the statues have a meaning.)

that's because i feel the distinction between meaning and formal semantics 
is central to keeping everything straight.  (and, since experts tend to use 
'semantics' to mean formal semantics: i feel the distinction between 
meaning and semantics is central to keeping everything straight.)

the (set-theoretic) semantics of a model element might be some set, but the 
model element does not mean some set, it means a certain item in the system.

or, if we don't want to use 'to mean' in that way, then the appearance of 
an element in a model does not mean there is a certain set, it means there 
is to be a certain item in the system.

but that is just to explain my frequent confusion.  i don't mean to suggest 
changes to the technical language used by experts.  i know that 'x means' 
is often used by experts to mean the image of x under the interpretation is.

Again, thanks for the careful elucidation.


At 10:17 AM 9/7/2002, Tony Simons wrote:
>Hi again,
>
>Joaquin Miller wrote:
>
>=====
> > > >A consequence of the semantic domain design principles is that the
> > > >semantic domain should not contain equivalences; i.e. all semantic
> > > >elements denote distinct concepts.
>
>One possible reading:
>    semantic elements are the items in the semantic domain
>    the items in the semantic domain denote concepts
>=====
>
>Well I can't really comment on the wording of the 2U document, but I
>I read this as meaning that each element in the semantic domain is
>unique (not equivalent to any other in the domain) and therefore a
>denotation of a distinct element from the UML model.  I don't think
>that there's meant to be another level of concepts below the semantic
>domain, which somehow explains that domain.  Granted, the wording does
>seem a bit fluffy.
>
>It would have been easier to say:  "Because of the way the semantic
>domain is constructed, elements in the domain are unique.  No element
>is equivalent to any other."
>
>This would have avoided introducing "concepts" which seems to be the
>source of the confusion.  I haven't seen the full context of the above
>statement, but the "concepts" may refer to UML model elements, in which
>case I would read this as meaning: "if two model elements are denoted
>by different semantic elements, then they are distinct".
>
>My preferred answers to your questions are therefore:
>
> >  Which are the concepts that the items in the semantic domain (the
> > "semantic elements") denote?
>
>-- elements from the semantic domain are the denotations (interpretation)
>    of UML model elements;  it is reasonable to say that they "denote the
>    concepts" (from the model layer above)
>
> >  Where are those concepts found?
>
>-- these "concepts" are just ordinary elements of UML models, whose
>    meaning is given by the mapping to elements in the semantic domain
>
> >  What do those concepts denote?
>
>-- probably not a well-formed question; they model some aspect of the
>    software system under consideration, but "denoting" may be the
>    wrong term, since the relationship is one of abstraction rather
>    than precise characterisation.
>
> >  Where do we find the meaning of those concepts?
>
>-- well, the meaning of the concepts-as-UML-elements is given in the
>    semantic domain;  the meaning of the real world/system is more
>    tricky!
>
>I hope this helps,
>
>--Tony
>
>==========================================================================
>
>Dr Anthony J H Simons                   a.simons@dcs.shef.ac.uk
>Senior Lecturer in Computer Science     http://www.dcs.shef.ac.uk/~ajhs
>Director of Teaching
>
>Department of Computer Science          tel:  (+44) 114 22 21838
>University of Sheffield                 dept: (+44) 114 22 21800
>Regent Court, 211 Portobello Street     fax:  (+44) 114 22 21810
>SHEFFIELD, S1 4DP                       univ: (+44) 114 22 22000
>United Kingdom
>
>==========================================================================


PGP Fingerprint:
CA23 6BCA ACAB 6006 E3C3 0E79 2122 94B4 E5FD 42C3

Date view Thread view Subject view Author view Attachment view