Re: RDF Issue rdfms-literalsubjects

From: "Pat Hayes" <>

> >I don't understand this "damage" to syntax.  What are the problems with
> >using something like "rdf:aboutLiteral" instead of "rdf:about" where the
> >subject is a literal?   I gather that there is no problems with the
> >semantics of using literals for subjects.
> There are some syntax issues. One problem arises as follows. Imagine
> that we allow literals as subjects, and we have the following kind of
> situation
> [1] aaa --ppp---> "13" ---qqq---> bbb
> [2] ccc --rrr-->"13" ---sss--> ddd
> Now if we have 'tidy' literals - which many people want to, for
> technical reasons - then those two literals have to be the same node;
> and then we have a graph with five nodes consisting of a literal with
> two triples coming 'into' it and two triples coming 'out of' it,

True .. see graph:

>but no way to tell which goes with what.

This seems to me to be a feature and not a bug ...  I guess I don't
understand your concern.  The literals would function just exactly like URI
.. syntactically and semantically.  The only difference I can think of would
be any difference in the criteria for syntactic equality of literals as
opposed to the criteria for syntactic equality of URI.

>If these were blank nodes we
> could just use two nodes, but the literal labels will *force* the
> nodes to be merged (if nodes are tidy).

Yes I'm assuming tidy literals.  You seem to be saying that the statement
sets (that I marked above with [1] and [2] ) need to be kept separate
somehow ... why?

> And there are also some issues with using the Ntriples
> syntax with literals as subjects.

Yep, big change:
subject ::= uriref | namedNode | literal

>And, of course, XML introduces yet
> more syntactic conditions.

I don't see why  ...
<rdf:Description rdf:aboutLiteral="N-Triples Internal Working Draft">
would not flow through XML just fine ?

> So one way and another,
> it is a bit of a  mare's nest.

Well I can see a lot of documentation that would need to be changed .. but I
can't see any technical problems with just doing it ... can you?  On the
other hand I can see a lot of other things that could start happening very
simply.  For example, we could just start talking about concepts like "The
Coherence Theory of Truth" or "Pat Hayes"  without having to make a URIs for
them.  Now is that heresy .. or what?

Seth Russell

Received on Sunday, 24 February 2002 21:48:17 UTC