Re: [wg@2uworks.org] Book



Date view Thread view Subject view Author view Attachment view

From: Andy Evans (andye@cs.york.ac.uk)
Date: Mon 09 Sep 2002 - 19:35:24 BST


And Jos Warmer has found building such tools from a semantic domain model
(as is presented in the OCL 2.0 model) very straightforward.

Andy
----- Original Message -----
From: "Stuart Kent" <stuart@mclellankent.com>
To: "Joaquin Miller" <joaquin@acm.org>; <puml-list@cs.york.ac.uk>; <wg@2uworks.org>;
<discussion@2uworks.org>
Sent: Monday, September 09, 2002 7:35 PM
Subject: Re: [wg@2uworks.org] Book


> Joaquin
>
> At 11:05 09/09/2002 -0700, Joaquin Miller wrote:
>
> >>The key point about that discussion is that one must be able to look at
> >>an element of the semantics domain (which will be described in some
> >>language) and point to something in the real world and say "this element
> >>corresponds to that thing". Let me give a small example. It is hard to
> >>point to a thing in the world that corresponds to the class "Book".
> >>However, you can point to things (i.e. particular books) that correspond
> >>to objects (elements of the semantics domain) in a denotation of the
> >>class "Book"
> >
> >Thank you Stuart.  This is the first time i have seen any motivation
> >offered for excluding objects from the modeling language or excluding
> >classes from the semantics domain, or splitting UML into two parts, or
> >whatever it is that 2U is up to.  (My choice of words just indicates that
> >i don't grok it yet.)
>
>
> >It is certainly true that there is nothing to point to, which is the (oh,
> >oh!  here goes:) denotation of 'book.'    This is the cause of much
> >trouble, and if 2U has found a way to avoid the trouble, that's great.
>
> I sense doubt in your "tone". There is also a very pragmatic reason for our
> approach.
>
> When I build models with most current UML tools I don't get to exercise the
> model until I get to writing code that implements it. When I write code I
> set up tests, with test data, that allow me to generate sample traces that
> I can then examine - either through a debugger, or by what my program
> reveals about its execution traces through the UI, what it writes to log
> files or standard output, and so on.
>
> I would like to be able to exercise a model before it reaches the code
> stage and view it's traces "through the eyes" of the model. The semantics
> domain essentially defines the space of traces for a UML model. An instance
> of the semantics domain represents a trace of a particular model. The
> mapping from abstract syntax to semantics domain (the semantics) gives the
> rules for determining whether a trace is valid for a particular model. If I
> use a subset of UML which is executable, then this mapping will give the
> rules for calculating a trace from a starting state and with subsequent
> input of external events. So implementing the semantics domain metamodel
> and the semantics mapping metamodel will, at worst, provide a tool that
> allows one to set up traces manually and check whether or not they satisfy
> the model, and at best will give you a tool that directly interprets a
> model, if it is executable. In practice, one will probably get something
> in-between. Traces may be partially generated with some decisions made by
> the modeller. One can also imagine running the mapping backwards, and
> learning a model from a set of traces (e.g. when business modelling, you
> model the examples first, as it is often easier to talk examples to get an
> understanding of the more general concepts). Now imagine an MDA scenario
> where model maps to code, and then traces of executing code map to traces
> "through the eyes" of the model. By monitoring implementation traces, one
> could use the latter mapping to provide you with a "dashboard" application
> to view executing systems through the eyes of the business model, for
> example. And so on.
>
> So you see our motivation is not philosophical, but practical. It so
> happens that taking the trouble to define semantics in this way also means
> that we have a means of discussing subtle aspects of the meaning of the
> language, that tend to lead to lots of confusion and misunderstanding if
> not pinned down and explicitly modelled (viz. all the recent discussions on
> U2P definition of association and association generalization).
>
>
> >It is, though, pretty easy to convey to one's interlocutor what is meant
> >by 'book.'
> >
> >(Though, like all words, there will be what some call variants or
> >extensions around the central cluster.  Last week at the Berkeley art
> >museum i saw a book made from two cigarette packs, with illustrations
> >drawn on the white sides, opened flat, trimmed, and then folded together
> >and hand sewn.  And that is pretty close, compared to the various meanings
> >of 'book' in accounting, card games,  criminal prosecution, and bookmaking
> >(the other meaning of 'bookmaking'); card games being the outlier here.)
> >
> >
> >
> >_______________________________________________
> >wg mailing list
> >wg@2uworks.org
> >https://2uworks.org/mailman/listinfo/wg
>
>
>
>
> To remove yourself from this list please mail puml-list-request@cs.york.ac.uk
> with a message containing the word "unsubscribe".
>
>

Date view Thread view Subject view Author view Attachment view