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

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Tue, 22 Jan 2002 17:08:23 -0600
Message-Id: <p0510103bb87394c74465@[]>
To: Patrick Stickler <patrick.stickler@nokia.com>
Cc: w3c-rdfcore-wg@w3.org
>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
>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".


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.

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Received on Tuesday, 22 January 2002 18:08:22 UTC

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