W3C home > Mailing lists > Public > semantic-web@w3.org > January 2010

Re: Requirements for a possible "RDF 2.0"

From: Jeremy Carroll <jeremy@topquadrant.com>
Date: Tue, 19 Jan 2010 22:55:06 -0800
Message-ID: <4B56A8CA.7000605@topquadrant.com>
To: Harry Halpin <hhalpin@ibiblio.org>
CC: Pat Hayes <phayes@ihmc.us>, Kjetil Kjernsmo <kjetil@kjernsmo.net>, semantic-web@w3.org
In line question ...

Harry Halpin wrote:
> No, but the spec should allow a competent Python/C/Ruby/etc.
> programmer to read it and understand RDF, and the implement compliant
> software. Essentially, specs should, IMHO, be aimed at implementers,
> while the tutorial stuff can be aimed at users and of course does not
> need to spec.
>  I am noticing that while the current RDF specs are very thorough, and
> the editors deserve  lots of credit for that, they should be
> simplified. 
Harry, with the RDF specs I think we had this aim in mind. Please 
enlighten me as to where we failed.
My take is that:
RDF Concepts - tells you the basic data structure, with clarity to 
design the API into the data structure for your programming environment
RDF Syntax - tells you how to take an XML document and populate above 
data structure
RDF Vocab - gives you some vocab

I think this desire to simplify might mean to leave out some of the 
detail. This was the mistake we were trying to avoid.
A spec is like a computer program, if it doesn't have the detail then 
you get a nasty mess when someone tries to run that part of it.

We perhaps were too reluctant to undo the work of the first RDF WG, by 
explicitly marking rdf:Alt as bad.
I think it is left to the reader to interpret certain phrases like:

The intended mode of use is that things of type |rdf:Bag| are considered 
to be unordered but to allow duplicates; things of type |rdf:Seq| are 
considered to be ordered, and things of type |rdf:Alt| are considered to 
represent a collection of alternatives, possibly with a preference 
ordering. The ordering of items in an ordered container is intended to 
be indicated by the numerical ordering of the container membership 
properties, which are assumed to be single-valued. However, these 
informal interpretations are not reflected in any formal RDF entailments.
Whilst formally it is no different from an |rdf:Seq 
<http://www.w3.org/TR/2004/REC-rdf-schema-20040210/#ch_seq>| or an 
|rdf:Bag <http://www.w3.org/TR/2004/REC-rdf-schema-20040210/#ch_bag>|, 
the |rdf:Alt| class is used conventionally to indicate to a human reader 
that typical processing will be to select one of the members of the 

which actually do a pretty good job of making out that Alt is useful.

I note that RDF Semantics is aimed at a somewhat ambitious programmer. I 
think that is unavoidable. I also think Pat did an amazing job at making 
that have a wider possible audience than it might have done.

> For example, I know of implementers that go off and use
> rdf:Alt and reification, and because they arent on swig etc., they
> have no idea this is "bad practice". This common knowledge should be
> noted in the specs.
> The Semantic Web, unlike most other Web standards, is basically a
> research project - and a far-sighted and correct one it seems! -
> disguised as a standardization project, and so its not surprising that
> after a number of years, some concrete lessons have been learned. I
> see no reason to aim them at the spec.

This amused me!
> Most informal specs nowdays (see say, opensocial) go through a rapid
> evolution and feedback from developers phase, something that the "make
> spec once and never update" policy doesnt work to well with. There is
> probably a golden mean somewhere, where we can make and should make
> incremental updates to most specs every 5 or so years if they are
> still being used.
Received on Wednesday, 20 January 2010 06:56:37 UTC

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