W3C home > Mailing lists > Public > www-xml-schema-comments@w3.org > January to March 2000

Equivalence classes

From: Philip Wadler <wadler@research.bell-labs.com>
Date: Tue, 15 Feb 2000 15:54:00 -0500
Message-Id: <200002152054.PAA05811@nslocum.cs.bell-labs.com>
to: www-xml-schema-comments@w3.org, xml-dev@ic.ac.uk
cc: cmsmcq@acm.org, ht@cogsci.ed.ac.uk, matthew.fuchs@commerceone.com, dbeech@us.oracle.com
A request for clarification about equivalence classes.

If all elements are declared via top-level `element' declarations,
then I think that I understand how equivalence classes work.  Can
someone please explain how equivalence classes work in the presence
of element declarations nested within type declarations?

Also, I gather that equivalence classes are not really symmetric.
That is, declaring A with equivalence class B is not at all the
same as declaring B with equivalence class A.  I think this is the
right choice, but the schema specification needs to be clarified
and it would help to choose a name that did not imply symmetry.
In particular, I suggest exploiting the analogy with object-oriented
languages, and replacing `equivClass' with `super'.

-- P

Philip Wadler                             wadler@research.bell-labs.com
Bell Labs, Lucent Technologies      http://www.cs.bell-labs.com/~wadler
600 Mountain Ave, room 2T-402                   office: +1 908 582 4004
Murray Hill, NJ 07974-0636                         fax: +1 908 582 5857
USA                                               home: +1 908 626 9252
Received on Tuesday, 15 February 2000 15:56:03 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 23:08:46 UTC