Re: Access Languages are Tied to Schemas

Jonathan Robie (jwrobie@mindspring.com)
Thu, 20 Nov 1997 13:14:53 -0500


At 12:20 PM 11/20/97 -0500, Joe Lapp wrote:
>Joe Lapp <jlapp@acm.org> wrote:
>>[...] Do we
>>expect general SGML/XML repositories to be powerful enough to allow
>>them to represent almost any domain-specific object model?
>
>I don't like how I worded the question here. Let's try again: What
>sorts of object models do we want to be able to represent in SGML/XML?

Any object model, but with some limitations on the extent of the representation.

The following properties of object models are easily represented in SGML/XML:

o Identity
o State
o Type

These properties are not easily represented:

o Behavior (except for in languages that allow methods to be
represented as data, e.g. Java)
o Encapsulation constraints

There are indirect methods for describing inheritance in SGML/XML, but they
are different from the inheritance mechanisms in OO languages.

SGML/XML can represent the data and identity portion of any object model
expressed in C++, Java, CORBA, etc., including the reference network.

Jonathan