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From: mjhealy@unconfigured.xvnews.domain (Michael J. Healy 206-865-3123)
Subject: Re: mathematics (algebra?) of object orientation
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References: <nntpuserDIxvwE.39y@netcom.com>
Date: Tue, 5 Dec 1995 21:25:26 GMT
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Xref: glinda.oz.cs.cmu.edu comp.object:42119 comp.object.logic:617 comp.theory:14860 sci.math:127613

I just had a question and then a comment.

In article <nntpuserDIxvwE.39y@netcom.com>, scottw@advsysres.com  (Scott A. Whitmire) writes:
> In <49lvuq$bv1@mujibur.inmind.com>, mfinney@inmind.com writes:
> >   A class is a predicate.  This predicate includes sub-predicates that
> >specify the methods associated with the class.

How does a predicate include other predicates? Does "includes" mean "is a 
conjunction of"? (Sorry if this has already been explained---I just got here.)

  Each of those methods
> >is described by a predicate which includes a precondition predicate and
> >a postcondition predicate.  The class predicate is (potentially) more than
> >just the list of method definitions.  It can include additional constraints,
> >some of which can be second order and generally is quite complex.
> >
> 
> You may be on to something here. A question: how do you include attributes
> in your model? You only discuss the class and its methods.
> 
> Another approach is to say that a class is a set of properties (state and
> behavior) which can be described algebraically, at least the external view.
> Internally, you almost have to go with the "set theory" approach, since you
> are dealing with collections of things. (The set theory approach was
> mentioned in the material I deleted.)
> 
> This view, that a class is a set of properties, is derived from Ontology,
> which is basically the study of the structure and nature of things in the
> natural world - part science and part philosophy.
> 
> 
> 
> Scott A. Whitmire             scottw@advsysres.com
> Advanced Systems Research     
> 25238 127th Avenue SE         tel:(206)631-7868
> Kent Washington 98031         fax:(206)630-2238
> 
> Consultants in object-oriented development and software metrics.
> 
I don't know object-oriented programming at all, but it seems to me that there is a 
way to deal with classes and predicates, in fact several ways, all related.  I 
could use several key words here: Examples are type theory, geometric logic and 
(my favorite overall), category theory.  I don't want to intrude, but I wanted to 
mention this in case the concepts are new to people here.  My apologies if they 
are not.

Mike



