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Re: literal value terminology (was: Re: Review of MT)

From: Sergey Melnik <melnik@db.stanford.edu>
Date: Wed, 23 Jan 2002 18:21:37 -0800
Message-ID: <3C4F6FB1.F16C9377@db.stanford.edu>
To: Pat Hayes <phayes@ai.uwf.edu>
CC: Patrick Stickler <patrick.stickler@nokia.com>, w3c-rdfcore-wg@w3.org
Pat Hayes wrote:
> 
> >On 2002-01-19 4:21, "ext Sergey Melnik" <melnik@db.stanford.edu> wrote:
> >
> >
> >>  You know, I still would not use "datatype value". We kind of agreed to
> >>  use the terms "value spaces" and "lexical spaces" in datatyping such
> >>  that lexical spaces are subsets of what is currently called set of
> >>  "literal values". It seems more natural to baptize the elements of the
> >>  value spaces of datatypes as "datatype values"...
> >>
> >>  My counterproposal is just
> >>
> >>  I(literal token) = literal value
> >>
> >>  leaving datatypes out of the picture for now.
> >>
> >>  Sergey
> >
> >OK, I think I'm following you better now. You are in essence
> >saying that the current MT does *not* refer to members of
> >value spaces (as was Pat's assertion) but rather refers to
> >members of the lexical spaces.
> 
> No, that is a misunderstanding of the current MT. The phrase "literal
> value" in the MT document has always been intended to refer to items
> in the value space of a datatype, not the lexical space (both terms
> as used in XSD).
> 
> >Whether that fits into the MT as specified now or not, perhaps
> >we can iron out the terminology first, and then figure out
> >if the semantics of the terminology fit the semantics of the
> >MT?
> >
> >I propose
> >
> >    'literal'        the RDF/XML string representing an rdfs:Literal
> >    'lexical value'  member of lexical space of "some" datatype
> >    'data value'     member of value space of "some" datatype
> >
> >and the datatyping proposals focus on clarifying *which*
> >datatype a given lexical value or data value belong to.
> >
> >As to which of the above 'literal value' in the present MT
> >corresponds to, I can't say. Seems to me that it equates
> >to data value. Pat?
> 
> Right. Clearly we all have our choke points, and mine is using the
> term "value" for any kind of lexical token (in any syntax). So I
> really do not want to use any phrase with "value" in it to refer to
> anything in the RDF graph. That would confuse anyone with a logical
> or KR background as badly as "literal value" apparently confused
> Patrick. To me, "lexical value" sounds like an oxymoron (or else some
> terribly sophisticated idea involving metalanguage interpretations,
> or something like that.) I notice that both the XSD docs and Sergey's
> datatyping write-up seem to manage without any such term; they use
> phrases like "element of the lexical space".
> 
> Hmmmm. Seems to be impossible to keep everyone happy.
> It may be that the final decision on datatyping will make this entire
> discussion pointless, in any case. In the meantime, I think that for
> this version of the MT document I will just stick to plain 'literal'
> for the RDF/XML syntactic item (as this usage is already established)
> and find some textual way of saying that whatever these things denote
> is currently not specified, but that a more complete story will be
> told in a future edition, and just try to avoid using any terminology
> (notably "lexical value") that might be confusing. I will just say
> they are in a set XL and refer to "elements of XL".

fine with me...

> Pat
> 
> PS. Let me try to review some of the issues. When discussing
> datatypes, there is an established terminology used by XSD: lexical
> spaces and value spaces. Sergey and I would both like to conform to
> that as far as possible, to be sure. However I think that our
> understandings of how to conform to it differ. My understanding
> always was that the things in a datatype lexical space would be
> identified with lexical items in RDF syntax, and things in the value
> space would be identified with semantic values. (Hence the P-style
> proposals, BTW, which try to incorporate the datatype mapping into
> the MT as a special kind of interpretation mapping.) I think (?) that
> Sergey's understanding is that the domains that arise in datatyping -
> lexical spaces and value spaces - *both* belong in the semantics of
> RDF, and that the lexical items in RDF syntax that refer to them are
> something else altogether. Hence the 3-way distinction outlined
> above, which distinguishes RDF syntax from datatype lexical space. I
> can see how that would leave a terminological muddle surrounding the
> term "literal value" , which sounds (to Patrick and Sergey?) like it
> would be a (semantic) value which happened to be a literal, ie
> something in the lexical space of a datatype. That interpretation
> simply hadn't occurred to me, I confess.

This is a perfectly accurate analysis, Pat, and a very nicely worded
one. In fact, as obvious as it is, it did not occur to me that elements
of lexical spaces (per XSD) could simply be identified with RDF literals
(i.e. literal tokens ;)

The question is whether we go with a 2-way or a 3-way distinction. It
looks like this issue needs to be clarified in the "foundations" part of
the datatyping document. The 3-way distinction seems somewhat more
general. Are there any caveats? Which one would you prefer?

Sergey
Received on Wednesday, 23 January 2002 20:52:07 EST

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