XML and RDF Schema

Author: Dan Brickley <danbri@w3.org>
Last updated: $Id: Overview.html,v 1.3 2001/07/11 20:22:15 danbri Exp $

Status of this Document

This is very rough; I wanted to get the shell of a document in place so i could try to improve it incrementally as I find time. Or involve others in doing so. If you send me suggestions I'll try to incorporate them; find me via IRC if you are interested in contributing.

Overview

This document provides an overview of some work on Schema language convergence. Specificially, it provides some technical references for developers who ask the frequently asked question "Why do we have both an RDF Schema language and an XML Schema language.

Contents

• Background (cambridge communique; webdata)
• Recent Work
• Future Developments

Background

Since 1997/8, W3C has been working in parallel on both an RDF Schema language and an XML Schema language. During August 1999, W3C convened a meeting of working group members from the XML and RDF groups to discuss the relationship between RDF Schema and XML Schema, and more broadly, between RDF and XML. The immediate result of that meeting was the Cambridge Communique W3C Note. Work has subsequently proceeded on both XML and RDF Schema; this document summarises some recent developments.

Additional background material can be found in the W3C Note Describing and Exchanging Data (June 1999). That document provides an overview of the RDF and XML information models, and outlines some possible areas of convergence and mutual interest.

Recent Work

Since the Cambridge Communique, work has progressed both on the key specifications (XML Schema is now a Recommendation; RDF Core WG has been chartered) as well as on implementations. While there is no W3C specification for anything like a "unified schema language", various technical issues are now clearer than they were in 1999.

RDF and XML: many relationships

RDF and XML are related in many ways. (@@todo: find references. I'm listing everything I can think of here first)

• RDF 1.0 Syntax uses XML
• Future alternate RDF syntaxes use XML (eg. TimBL or Sergey proposals)
• Other RDF-like systems (topicmap graphs; SOAP graph encoding) use XML representations
• XLink typed references can be modelled in RDF
• XSLT can be used to transform colloquial XML syntaxes into RDF
• XML Schema provides an 'annotation' construct to allow mappings into RDF to be specified (see also Schema Adjunct Framework (google links)).
• XML Schemas part 1 (Structures) tells us that an XML Schema parses into an edge-labelled graph
• XML's Infoset can be modelled in RDF (W3C Note)
• The post-schema-validated infoset can be modelled in XML
• RDF Core WG is chartered to write a document relating RDF to the wider family of XML technology; and to complete work on datatyping in RDF, building on XML Schema work
• XML Schema publishes URIs for datatypes (etc)

Implementations

Links to published implementations belong here

• XSLT XML into RDF view of infoset
• Schema Adjunct Framework
• DAML+OIL use of XML Schema datatypes. DAML; DAML+OIL Web Ontology Language (based on RDF); reference description (March 2001 version). This proposes a model for using XML Schema datatypes within RDF.
• The RDF-Calendar group have a real world use case: representing dates of events using RDF. Some drafts sent to that list use XML Schema datatypes for this. A thread from the XML Schema developers list is relevant.
• XML with Relational Semantics (Sandro Hawke); code in CVS
• ...

References

XGraph doc has some details; xml proc w/shop paper; ...

A Story about RDF and XML

Acknowledgements

thanks for suggestions / feedback / content to: Aaron Swartz, ....

Recent Changes

Recent changes to this document include...

$Log: Overview.html,v $
Revision 1.6  2001/07/11 20:36:16  danbri
fixed rdf-calendar list and added link to the xmlschema-dev thread  on dates

Revision 1.5  2001/07/11 20:33:06  danbri
added acknowledgements section, and link to IRC channel for contributors