New issue - Meaning of URIs in RDF documents

From: Tim Berners-Lee <>
Date: Mon Jun 30, 2003  15:05:02 US/Eastern
Subject: New issue - Meaning of URIs in RDF documents

The Semantic Web Coordination group at its meeting of 2003-06-30  and 
passed on to the Tag the issue which had been loosely described in RDF 
circles as "social meaning".  As background,

- The URI specification defines URI syntax and explains that each URI 
identify one thing ("Resource": concept, etc).
- RDF documents use URIs as identifiers for things including for 
relations. An RDF statement "S P O" means that a given binary relation 
identified by P holds between to things identified by S and O. (S, P 
and O are URIs)
- The HTTP specification provides for a set of URIs which have (a) 
delegated ownership (b) publication and retrieval of information 
- The OWL specification is a vocabulary of properties allowing an RDF 
document to say things about RDF Properties
- The TAG has written on the desirability of using dereferencable URIs, 
and of actually publishing relevant and useful information.

The combination of these architectural parts allows information to be 
published so that the recipient of an RDF statement  "S P O" can, by 
dereferencing P, get information about the relation being asserted. 
This information, directly or indirectly acquired, may be 
human-readable and/or machine readable, the latter including for 
example ontological statements in OWL, or rules, or other logical 

The community needs

1) A concise statement of the above architectural elements from 
different specs in one place, written in terms which the ontology 
community will understand, with pointers to the relevant specifications.

2) Some outline guidance on specific questions brought up in email 
- Is a given inference engine expected to take into account a given 
document under given circumstances?
- how does one avoid having to commit to things one does not trust?
- etc etc etc

3) There may be some need to clarify frequent misunderstandings by 
making some things clear.

-  the architecture is that a single meaning is given to each URI (such 
as P), that the URI ownership system makes statements by owners 
authoritative weight, despite what other documents may say.
- the architecture does not permit the meaning of a URI to be changes 
by consistent misuse by others.
- that use of a URI in RDF implies a commitment to its ontology, and if 
there is doubt as to what ontology that is, the web may be used to 
resolve it.
- that the web is not the final arbiter of meaning, because URI 
ownership is primary, and the lookup system of HTTP is though important 
secondary. (That is, if you hack a web server's ontology files, you do 
not change hat the URI means, you just break a machine for a while)
- etc etc.

The proposal is that a draft finding be written which pulls this 
together, with elaborations pointing into the various specs. Members of 
the SWCG have volunteered and some members of members of the SWCG have 
been volunteered to read early versions.

tim bl

Received on Thursday, 3 July 2003 10:41:53 UTC