Semantic Web Update - W3C RDF and OWL standards, development and applications

, RDF

Dave Beckett
Institute for Learning and Research Technology (ILRT), University of Bristol
Bristol
UK
http://www.dajobe.org/

Biography

Dave is a researcher at the ILRT, University of Bristol and works on the Semantic Web Advanced Development Europe (SWAD-E) project. He has been working with metadata and the Dublin Core since 1995, RDF since 1998, is a member of the W3C RDF Core Working Group, and editor of the RDF/XML syntax W3C working draft. Dave is the author of the Redland and Raptor RDF tools.


Abstract


As of early May 2003,the current revising of RDF by the W3C RDF Core Working Group is substantially complete -- processing the comments from the published Last Call working drafts is mostly done. The Web Ontology working group producing the OWL Web Ontology Language from earlier DAML+OIL work, based on RDF has also just completed its main technical work and reached the last call stage, so this is an appropriate point to explain the current W3C progress. This update covers what has been changed from earlier developments based on implementation feedback, an outline of the state of the current and imminent publications as well as an overview of the W3C Semantic Web activity.

An outline is given of the state of the active research activity including the SWAD work in Europe and US, RDF Query and Calendaring task forces, the ongoing coordination of RDF and XML in various areas such as XML schema datatypes, schema annotation and with Web Services such as WS Choreography.

Finally the update will describe some of the latest semantic web applications in development that should include at least the following: self-described personal information (FOAF), flexible and simple syndication (RSS 1.0), semantic web links with webloging (pings, trackback, RSS), description of real world locations (spacenamespace, GeoURL, related to events).


Table of Contents


Introduction to W3C Semantic Web Activity
RDF Core Working Group
     RDF/XML (Revised)
     RDF Semantics
     RDF Concepts and Abstract Syntax
     RDF Primer
     RDF Test Cases
     RDF Vocabulary Description Language
Web Ontology Working Group
     OWL Guide
     OWL Reference
     OWL Abstract Syntax and Semantics
     OWL Test Cases
RDF Interest Group & Task Forces
Semantic Web Development
Semantic Web Coordinatation and Liason
Latest Applications
Conclusions
Bibliography

Introduction to W3C Semantic Web Activity

The World Wide Web Consortium (W3C) has operated the Semantic Web Activity since early 2000, replacing the previous Metadata Activity. It's goal is to enable computers to gather better information from the web in a way that can be better used and re-used that that targeted for humans - such as markup formats like HTML.

The W3C Semantic Web work was designed based on several technologies, with the core technical work based upon the RDF (Resource Description Framework) as a general descriptive framework with the minimum of constraints and vocabulary. Later work builds upon it to provide further layers such as simple vocabulary description (RDFS) and more recently the OWL (Web Ontology Language) to allow richer definition of classes, properties, their relationships and constaints.

The activity consists of two Working Groups (WGs) - RDF Core and Webont, education and outreach via the RDF Interest Group via a mailing list, collaborative spaces (IRC, wiki) and events along with related lists on specific topics or areas: rdf-logic for logic-based languages such as OWL, rdf-calendar for modelling events and calendaring issues and rdf-rules for querying and rules.

XML is both the basis for the syntaxes of each of the languages - they are all written in terms of RDF, and it has an XML transfer syntax called RDF/XML - and the W3C XML schema atomic datatypes are used in RDF and OWL for describing simple (non-complex) datatypes in the instance data.

RDF Core Working Group

The W3C RDF Core Working Group [RDF Core WG] has members and invited experts from a mixture of industry, research and education. RDF Core was charged to revise the existing RDF Model and Syntax Recommendation[RDF Model and Syntax] from 1999 and complete the work on the RDF Schema [] document from 2000. This involved handling the over 50 comments received on these documents as well as updating in light of implementation and deployment considerations. The charter also required updating the formalization of RDF's theoretical foundation using XML Schema datatypes and coordination with other WGs via the new W3C Semantic Web Coordination Group. The group was forbidden to make a new XML syntax.

The revising work has involved clarifying the original work where it was found to be unclear and also deciding on issues that were either not in the original documents or were out of scope. This has meant both changing, adding and removing semantic and syntactic parts of the model and the syntax. As the WG proceeded, the WebOnt working group was formed and brought it's own requirements on RDF that had to be reflected in additional changes beyond those anticipated initially.

RDF/XML (Revised)

The current working draft for the RDF/XML Syntax [RDF/XML Syntax Specification (Revised)] re-expresses the syntax based as a on the [XML Information Set] in the style of a SAX-like stream of events. [RELAX NG Non-XML Syntax] is used in the document a help to check the structure of RDF/XML and [XML Base] support was added as a useful addition to the language. The specification is also being updated for better internationalization support after the recent [Character Model for the WWW] .

RDF Semantics

for model theorietic semantrics experts

RDF Concepts and Abstract Syntax

foo

RDF Primer

for a quick introduction to the rdf standards

RDF Test Cases

including the N-Triples test case language

RDF Vocabulary Description Language

The standard formerly known as RDF schema

Web Ontology Working Group

W3C Web Ontology Working Group [WebOnt WG] Number of members - 50+ Three languages? Three-into-onw? OWL - lite, DL, full. Why 3, what's in them. DAML+OIL standardised, with feedback.

OWL Guide

foo

OWL Reference

foo

OWL Abstract Syntax and Semantics

foo

OWL Test Cases

not currently a last call working draft

RDF Interest Group & Task Forces

RDF Query Calendaring (Geographical information emerging)

Semantic Web Development

SWAD work in Europe and US

Semantic Web Coordinatation and Liason

Inside W3C - RDF and XML with XML schema datatypes, schema annotation and with Web Services such as WS Choreography.

Latest Applications

self-described personal information (FOAF), flexible and simple syndication (RSS 1.0), semantic web links with webloging (pings, trackback, RSS), description of real world locations (spacenamespace, GeoURL, related to events).

Conclusions

Bibliography

[RDF Model and Syntax]
O. Lassila and R.R. Swick, 22 February 1999, RDF Model and Syntax Specification, W3C Recommendation, http://www.w3.org/TR/REC-rdf-syntax/.
[RDF Schema]
D. Brickley and R.V. Guha (eds.), 23 January 2003, RDF Vocabulary Description LanguResource Description Framework (RDF) Schema Specification 1.0, W3C Working Draft, http://www.w3.org/TR/rdf-schema/.
[RDF/XML Syntax Specification (Revised)]
D. Beckett, 23 January 2003, RDF/XML Syntax Specification (Revised), W3C Working Draft, http://www.w3.org/TR/rdf-syntax-grammar/.
[XML Information Set]
J. Cowan and R. Tobin, 24 October 2001, XML Information Set, W3C Recommendation, http://www.w3.org/TR/xml-infoset/.
[RELAX NG Non-XML Syntax]
J. Clark, 2001, RELAX NG Non-XML Syntax, http://www.thaiopensource.com/relaxng/nonxml/.
[XML Base]
J. Marsh, 27 June 2001, XML Base, W3C Recommendation, http://www.w3.org/TR/xmlbase/.
[Character Model for the WWW]
M. Dürst et al, 20 February 2002, Character Model for the World Wide Web 1.0, W3C Working Draft, http://www.w3.org/TR/charmod/.
[RDF Core WG]
W3C RDF Core Working Group, http://www.w3.org/2001/sw/RDFCore/.
[WebOnt WG]
W3C Web Ontology Working Group, http://www.w3.org/2001/sw/WebOnt/.