Derivation by Restriction

Fabio Arciniegas A. l-arcini at
Sat Jan 22 21:28:31 GMT 2000

Nikita said:
> IMHO, the OO principles _can_ be expressed by Schema.
> (OO languages is a subset of Schema or Schema is an extension of OO
> languages). 
> . So there is no matter how you describe this:
> by making iheritance with extension/restriction or by writing all the
> children for each element. Derivation in schema is provided for a little
> more convinience. 

Hi Nikita,

I think saying that "Schema is an extension of OO
languages" is plain wrong(and a bit weird), but well,that is not the
point at hand... 
Since I think you are seeing my last mail a bit simplistically I will
try to rephrase it,so I don't mislead others:

During the writing of some C++ classes for the representation of data
conforming with a particular schema I began to wonder about the
"translation" of an arbitrary schema to domain specific objects
(pretty much in the way exactml or some oracle products do nowadays
with DTDs) and I started to wonder about the implications of
derivation by restriction.

What I'm looking for is whether the impedance of Der. by Rest. on OO
apps/representations has been considered by anyone before...(not a
basic description of how derivation works,Nikita.But thanks).

So it's more of an open question about the rationale of derivation by
restriction... how necessary, really convinient is it? is this
translation to Domain specific objects a unique case of *possibly*
negative impact? (btw, I admit it would only be a problem to the
conformance principle in some translations... there are workarounds).

>From private responses to my post, it seems the question about the
rationale of derivation by restriction is not only in my
mind... sure Derivation by Restriction will be an additional burden to
implementors, so it sure has a good rationale behind it...


Fabio Arciniegas A.		        Viaduct Technologies, Inc.
fabio at			Software Engineer
Interests: XML, Wittgenstein and just about everything in between.
Oblique Strategy of the day: 	      "Abandon normal instruments"

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