Re: (Part 2) Where did these syntax constraints come from?

From: Peter F. Patel-Schneider (pfps@research.bell-labs.com)
Date: 01/09/01 

From: pat hayes <phayes@ai.uwf.edu>
Subject: Re: (Part 2) Where did these syntax constraints come from?
Date: Tue, 9 Jan 2001 12:47:08 -0800

> >TBL> <restrictedBy>
> >TBL>   <Restriction>
> >TBL>      <hasValue>
> >TBL> I hoped that the english would improve.  It is still really
> >TBL> non-evident from the markup what the restriction is. Also, it is a
> >TBL> wasteful use of markup. It is an example of excessive reification.
> >TBL> But I can't think of a better alternative.
> >
> >Yes, it's not pretty. If you have a better idea, say it NOW, or it will
> >be frozen.
> 
> Well, how about just eliminating the <Restriction> brackets, which as 
> far as I can see serve no useful purpose:
> 
> <restrictedBy>
>     <hasValue>
> 
> and eliminating </Restriction> at the other end? We know this is a 
> restriction since it follows <restrictedBy>, so why do we have to say 
> so again?

We have to say it again so that RDF will know it.  :-)   As RDF does not
have a semantics, we cannot count on range information having any meaning
in RDF.  :-(  If we could count on range information, then we could use

<restrictedBy>
   <rdf:Description>
      <hasValue>
...

but this would not be much shorter>   :-)


Actually, I think that the abbreviated syntax for RDF requires that a
property (like restrictedBy) contain a single resource.  Look in section
2.2.2 of the RDF spec for a not-very-readable discussion of this aspect of
RDF.

peter

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