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Re: Datatyping Summary

From: Sergey Melnik <melnik@db.stanford.edu>
Date: Mon, 04 Feb 2002 17:42:51 -0800
Message-ID: <3C5F389B.2FFDFC1E@db.stanford.edu>
To: Jeremy Carroll <jjc@hplb.hpl.hp.com>
CC: Graham Klyne <Graham.Klyne@MIMEsweeper.com>, Brian McBride <bwm@hplb.hpl.hp.com>, RDF Core <w3c-rdfcore-wg@w3.org>
Jeremy Carroll wrote:
> This message addresses the main criticisms of TDL.
> I will follow up with more detail concerning query, Brian's B3 & B4.
> The proponents of S furnish us with an implementation of S, and a model
> theory for S (which includes, naturally self-entailment).
> I now can create an implementation of TDL in the following fashion.
> As I read in any RDF graph I apply the following syntactic transformation.
> Match:
>   ?x  ?y ?z
>   where ?y != rdf:value and
>         ?z a literal node
>   replace with
>   ?x ?y NewNode
>   NewNode rdf:value ?z
>   where NewNode is a newly minted bNode.


I do like your suggestion, although I see it from a slightly different
perspective than DanC. In fact, your proposal is very much in the spirit
of the "flower power" posting I sent (which means we are on the same
track!). I think DanC got upset because it sounded like the above
expansion should be the default for RDF parsers. If, instead, we could
use a special flag in the syntax to indicate the desired parsing
behavior, we won't run into complications ("HUGE change" to RDF 1.0
stressed by DanC). With this addition, I'm a fat green light ;)

> For example:
> <a> <foo> "ss" .
> is transformed to
> <a> <foo> _:b.
> _:b <rdf:value> "ss".

Just a remark: I think it'd be stylistically better to avoid saying "the
triples ... are transformed into triples ...". Better: "RDF/XML document
... is transformed into triples ...", to avoid misunderstanding.
> We then use the S implementation and S model theory (idiom S-P is the only
> idiom used).

Pretty much so. I could live with S-P only. Again, CC/PP and DAML folks
might oppose trashing S-B. I wouldn't like disposing of S-A completely
just for the reason that S-A supports datatyping decoupled from lexical
representation, and S-P does not. However, I could live without S-A and
without S-B.

> Hence:
>   If S is implementable then so is TDL
>   The maximum overhead required for TDL is the same as that for S idiom A
> and/or S idiom P.
> All problems to do with entailment, query, implication, etc. are clarified
> and addressed with this process (as long as they are clear and addressed
> with S).

> >From an implementators point of view, it is clearly easier to implement the
> syntactic transformation and S-P, than to implement S-A, S-B and S-P.

Yep. I think Patrick pointed out that he could live even without the
syntactic transformation, i.e. parsing is always tidy, so that untidy
literals must be represented explicitly (I hope I'm not misrepresenting
Patrick's view). Seems like implementor's effort remains the same, but
no tweaking of the syntax is required. What's your opinion?
> Graham, does this adequately address your concern about self-entailment?
> [Small technical detail:
> S-P uses a closed world assumption on data types, whereas TDL uses an open
> world assumption. The two can be made equivalent by using S-P with at least
> two incompatible types in its closed world  both having domain being the
> complete set of unicode strings. Two such types are:
> xsd:string = { < x, x > | for any unicode string x }
> appendA    = { < x, x."A" > | for any unicode string, . being string
> concatenation }

This I don't understand... I think I missed all your closed-world
related explanations.
Received on Monday, 4 February 2002 20:25:56 UTC

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