Re: Contexts and email@example.com (John F. Sowa)
Date: Thu, 1 Jun 1995 12:16:54 +0500
From: firstname.lastname@example.org (John F. Sowa)
To: email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
Subject: Re: Contexts and views
Cc: email@example.com, firstname.lastname@example.org, email@example.com
>Our notion of contexts would seem to be rather different than John's.
>In our system, its not possible to look inside of a context from
>outside. Instead, to "see" the facts, definitions, etc. in a context,
>you must be in it, or in one of its children. This is in accord
>with normal scoping rules.
I agree with this restriction. It's a basic assumption of CG contexts
>Also, we support
>multiple inheritance -- our context hierarchies are not limited
>to trees. We have quite a few users (mostly in the NL domain)
>who use the multiple inheritance feature. One way to reason
>with two different views/contexts is to create a new context
>that inherits both of them.
I'm not against multiple inheritance. I suggested the Algol-like
tree structure because of its simplicity and the 30 years of practical
experience with it in conventional programming languages. I think
that the tree-structured references of Algol are the minimal necessary
for knowledge sharing. But the modules in Modula and the packages in
We have also identified (but not yet implemented) a need for
an export feature (lifting). Often, one would like to reference some
of the objects in a context without inheriting that context.
That provides a second means for interviewing the contents
of a context without being in or below it.
Robert M. MacGregor firstname.lastname@example.org
USC/ISI, 4676 Admiralty Way, Marina del Rey, CA 90292 (310) 822-1511