heterogeneous DBsbrayman@zuben.ca.boeing.com (Bill Brayman)
Date: Fri, 10 Sep 93 15:14:59 PDT
From: firstname.lastname@example.org (Bill Brayman)
Subject: heterogeneous DBs
Jeffrey Van Baalen writes:
> Recently I have become interested in applying my work to translation
> between databases and have been shocked by the fact that database
> people don't try to represent the semantics of their databases. This
> is what is needed for my approach to have a chance.
Your statement about database people has both truth and falsity.
We are trying to deal with data semantics and databases. One of the
main problems is that databases, per se, don't carry much semantics
(i.e. ordinary commercial databases). The semantics are implicity in
the applications that use the databases. Our approach is to try to
factor out the semantics whereever they are. However, representing any
semantics beyond simple data structures, though, takes more
representational power than any declarative language yet devised with
the possible exception of KIF and Conceptual Graphs.
The real issue is that these so-called semantics must be encoded in an
executable form today, else databases wouldn't be practical.
Consequently, we find that in practice, most semantics must be captured
in software procedures, not the database. Hence many "database people"
as you call them, don't try. In the research community that
characterization is wildly exagerated because, in fact, logic and
object oriented database people are tackling the problem.
You will find that the Entity-Relationship community (IDEF and NIAM,
say) will take issue with you because that community has identified a
range of semantics that they do represent.
>From discussions in the Conceptual Graphs community (and I am sure
other knowledge processing camps), it is becoming clear that to
adequately represent rich semantics, one needs first a language solidly
based on predicate logic, secondly, one needs a lot of ontological
infrastructure (concepts, idioms, theories) that apply for any given
domain, and thirdly, one needs a reasoning engine that operates in this
environment. Database people, don't have this machinery at their
disposal, not to mention a lot of the rest of us who would like to.
This is a bit chatty, because I can't take the time to fuss with my
response to you. But since, I see so little traffic on this maillist,
and the topic has such practical significance, it may be worth just