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Re: XRDF - an eXtensible Resource Description Framework

From: Dan Brickley <danbri@w3.org>
Date: Mon, 29 Jan 2001 16:42:43 -0500 (EST)
To: Reinhold Klapsing <Reinhold.Klapsing@uni-essen.de>
cc: <www-rdf-interest@w3.org>
Message-ID: <Pine.LNX.4.30.0101291409300.29497-100000@tux.w3.org>

Interesting proposal, though I'm left wondering whether it proposes a
fix-up to W3C's RDF or is a proposal for something different that happens
to have very a similar name (XRDF). I guess N3 is in a similar boat: is
it an RDF notation or an RDF-like system...?

This reminds me of a discussion that pops up occasionally: would RDF (and
similar models) be more easily understod if it had a name beginning with
'X' (XRDF, XML-Semantics, XGraph...?). My feelings on this are split;
while it could be seen as a shameless rebranding exercise on a par with
'Windscale' becoming 'Sellafield'(*), some such symbolic nod towards being
"part of the XML family of technologies" might have some value.


(*) Windscale/Sellafield -- a UK Nuclear power station, famously renamed
    (very powerful, though cracks and leaks appeared with age... ;)

On Mon, 22 Jan 2001, Reinhold Klapsing wrote:

> Dear RDF-IG members,
> we invite you to have a glance at the discussion paper:
> XRDF - an eXtensible Resource Description Framework
> Accessible at:
> - http://nestroy.wi-inf.uni-essen.de/rdf/xrdf/xrdf_v10.ps
> - http://nestroy.wi-inf.uni-essen.de/rdf/xrdf/xrdf_v10.pdf
> - http://nestroy.wi-inf.uni-essen.de/rdf/xrdf (XRDF-Home-Page)
> This paper presents a nested triple model for
> expressing relations found in the Web. The model
> allows grouping of atoms and statements on
> subject and object position. It preserves the
> structural context in which resource are used.
> Additionally, we propose a (pure) XML
> serialization syntax and a graphical
> representation which equivalently express the
> formal concepts. On top of the basic structural
> layer, semantic definitions and interpretations
> can be layered. One such layer is presented.
> Finally, the relation of this approach to RDF is
> discussed and it is argued, that most of the
> perceived deficiencies of RDF are non-issues in
> the context of XRDF.
> Below, you find a brief review of the key features and some general
> remarks on our intentions.
> Some key features are:
> -----------------------
> * A simple structural "model":
>   In the following definition, the (infinite)
>   alphabet A* will be used. A* will denote all
>   possible instances of PCDATA in well-formed XML.
>   We define the structure R recursively as an expression over A* as
>   R ::= r  |  R,R  |  [[R],r,[R]]
>   The terminals r denote elements of A*.  (you may call the possible
>   structures "resources", but we tried to keep it free from
>   interpretation even on this basic level)
> * A straightforward XML sntax correspong to the structural model,
>   <!ELEMENT statement (subject, predicate, object)>
>   <!ELEMENT list      (statement | atom)+>
>   <!ELEMENT atom      (#PCDATA)>
>   <!ELEMENT subject   (atom|statement|list)>
>   <!ELEMENT predicate (atom)>
>   <!ELEMENT object    (atom|statement|list)>
> * A graphical model directly corresponding to the structural model,
>   allowing for grouping/sequencing.
> * Some basic transformations are given, allowing to (de)reference
>   representations, to "dissolve" n:m,1:m,n:1 relations etc. These
>   basic tranformation can be used to embed the XRDF structures into a
>   host formalism (such as FOL) (or, in other words: to transform XRDF
>   expressions into "menaingful" expressions in other formalisms.
> Some general remarks:
> ---------------------
> We tried to keep the structural model, the
> synatactical and graphical representation and the basic
> transformations as free from interpretation as possible. Some will
> miss terms as "assertions" or "meaning/interpretation". This paper is
> a "part I" that tries to offer a simple (yet powerful) recursive "data
> model" with "positions" (based on triples again ;), a straightforward
> syntax that allows to "build" deeply nested expressions with complex
> (syntactical) structure (neat for "context"), and some basic
> (structural) transformations tied to "predicates" (that are the
> "things" in the middle of a triple). There is no semantics yet -
> instead we tried to provide the ingredients that allows to plug the
> XRDF stuff into suitable formalisms (by offering the tools that are
> needed to transform structured expression into a different "language",
> which may/should then be used to give meaning/interpretation to the
> XRDF constructs. We do not think that fixing interpretations on this
> level of langugae design is necessary or suitable - we feel that
> different interpretations in different formalisms should be possible
> easily. We hope that the discussion will show that there is much more
> to say.
> Please, allow one more word: we did not intend to "replace" RDF -- we
> have a simple RDF-to-XRDF converter online and a "XRDF flatener" is
> available in alpha version that allows, with a suitable set of
> additional semantic rules, to convert XRDF to RDF (using reification,
> position information, and dereferencing) -- instead, we thought that
> it might be fruitful to discuss a somewhat "clear-cut" approach to
> show which problems of RDF need to be tackled and how possible
> solutions may look like.
>  Thank you in advance,
>       Wolfram, Reinhold, Eckhart
> PS1: Any comments/questions/remarks are welcome. If
> you think that the question/comment is not (yet) of public interests,
> you may want to send it to rdf@nestroy.wi-inf.uni-essen.de only,
> otherwise, you may also want to CC it to the RDF-IG. We will collect
> all discussion on a Web page that will be accesible via
> http://nestroy.wi-inf.uni-essen.de/rdf/xrdf.
> PS2: We wrote the initial version Oktober 2000. We decided to submit
> it to the WWW10 conference -- mainly because, due to some unfortunate
> personal circumstances, there would have been no possibility to follow
> a possible discussion on the RDF-IG -- however, the paper was (and
> still is) initially intended to be a contribution to the RDF-IG. In
> the meantime, the time constraints have relaxed (so we are ready to
> start the discussion now! ;) and we have received the comments from
> the 3 reviewers. Two have been positive (7 and 6) (including
> encouraging comments) and one was negative (3) (without further
> comments) -- which is not enough to allow travelling to Hongkong but
> instead gives more time to work on discussing and improving the stuff.
Received on Monday, 29 January 2001 16:42:45 UTC

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