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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
http://www.w3.org/2000/07/hs78/KIF
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 
http://www.lfcs.informatics.ed.ac.uk/reports/91/ECS-LFCS-91-162/

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 GMT

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