- From: Ralph R. Swick <swick@w3.org>
- Date: Mon, 12 Feb 2001 08:06:38 -0500
- To: ht@cogsci.ed.ac.uk (Henry S. Thompson), "Sean B. Palmer" <sean@mysterylights.com>, "Jonathan Borden" <jborden@mediaone.net>, "Dave Beckett" <dave.beckett@bristol.ac.uk>, "David Megginson" <david@megginson.com>, <www-rdf-interest@w3.org>, <xmlschema-dev@w3.org>
At 08:27 AM 2/12/2001 +0000, Henry S. Thompson wrote: http://lists.w3.org/Archives/Public/www-rdf-interest/2001Feb/0068.html ... >Indeed, the one with a # on the end is a perfectly good namespace URI, >it's just not _the_ namespace URI for XML Schema, and documents with >that as their namespace will _not_ be recognised _by XML Schema-aware >processors_ as defined in the XML Schema spec. as being XML Schemas. yes, I concur. It seems to be a common misperception that RDF 1.0 _requires_ a specific character in the right-most position of a namespace URI. This was not the intention of the RDF designers and a careful reading of http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/ will reveal that neither "#" nor "/" is required at the end. Indeed, there was much discussion about whether RDF should choose a specific delimiter when concatenating the namespace name with the local name and it was decided to leave the full URI entirely within the scope of the namespace owner to define. At the present time, the XML language specifications do not endorse any use of a namespace URI other than string comparison with other namespace URIs. The RDF designers asserted from the beginning that we wanted to use URIs to their fullest , not just as strings to be compared. That is, RDF _expects_ that any URI can be presented to the Web for resolution. But RDF still treats URIs as "opaque" in the sense that RDF does not require any parsing of the URI. I acknowledge that, strictly speaking, opacity and concatenation are in conflict. However, I still do not think it was a mistake for RDF to rely on other characteristics of URIs as specified by RFC 2396. Sean wrote http://lists.w3.org/Archives/Public/www-rdf-interest/2001Feb/0066.html >you *cannot* restrict people >to using a few special characters at the end of their RDF namespaces, I disagree. We _could_ place such restrictions. But the primary reasons for requiring a specific delimiter eventually came back to an implication of endorsement on the act of parsing a property or class URI to extract its namespace. We want to make it clear that RDF does *not* endorse parsing URIs to extract RDF semantics. That is why RDF Schema proposes http://www.w3.org/2000/01/rdf-schema#isDefinedBy http://www.w3.org/TR/2000/CR-rdf-schema-20000327/#s2.3.5 So a proposed restriction to end all RDF namespace names with "#" or "/" was thought to be a gratuitous (unnecessary, unwarranted) constraint. I do feel a tiny bit of remorse for the confusion we have added by giving namespace name designers this extra freedom.
Received on Monday, 12 February 2001 08:07:56 UTC