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semantics of daml:equivalentTo [was: Comments on Annotated DAML 1.6]

From: Dan Connolly <connolly@w3.org>
Date: Wed, 11 Oct 2000 02:13:04 -0500
Message-ID: <39E41300.4DED37C2@w3.org>
To: Grit Denker <denker@csl.sri.com>
CC: www-rdf-logic@w3.org
Grit Denker wrote:
> Questions/comments on http://www.daml.org/2000/10/daml-ont.daml :
> o There were alternative IDs suggested for the property "equivalentTo":
>   equals, equiv, renames
>   I do not understand the semantics of this property.

Er... I'm not sure I do either. ;-)

To specify equality is to specify a whole logic,
as far as I can tell. I'm still puzzling over
issues like what set of objects quantifiers should
range over and such.
(see pointers into the KIF archives at
the bottom of
e.g. Chris Menzel 19 Dec 1993 )

For one logical framework
that looks really promising w.r.t. integration
of digital signatures[PCA], the definition of equality
takes about 3 pages of very dense LaTeX.

[PCA] http://www.w3.org/2000/07/DAML-0-5#PCA
(which is based on
A Framework for Defining Logics
Robert Harper, Furio Honsell and Gordon Plotkin 

I'm puzzling thru that paper, trying to understand
it by way of transcribing it in larch
http://www.w3.org/XML/9711theory/ELF )

This DAML-ONT specification just sorta waves its hands at
such hairy issues, in hopes that it doesn't matter
all that much for the purpose of marking up a few
pages and building a few tools.

When somebody builds a tool that can tell the
difference between one form of equality and
another, we'll have to get that sort of thing
nailed down.

>   Are there any implications/restrictions that assertions defined for any of
>   the properties hold true for both of them?

er... I'm not sure I understand that question, but I think
the answer is: yes; if I have equivalentTo(X, Y),
then anything I know about X I also know about Y.

>   Depending on the semantics one should choose the name of that property.
>   Personally, I do associate with "equals" a syntactical equality.
>   The term "equiv" in my view implies some kind semantic
>   correspondence/equality .
>   "Renames" is the term which has fewest implications on the semantics.

Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Wednesday, 11 October 2000 03:13:07 UTC

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