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⟶ CISD and DCI ⟶ Literature ⟶ W3C UK News (1998-2006)
⟶ CISD and DCI ⟶ Literature ⟶ W3C UK News (1998-2006)
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Further reading ⇓

□ Overview
1998
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1999
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2001
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2002
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2003
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Issue 11: November 1998

Resource Description Framework (RDF)

To add value to the data available on the Web, we need to find ways to represent information about that data; that is metadata. Metadata is data about data and can be used for many applications such as searching, cataloguing, etc. An example of metadata is a PICS label that is added to a web page to allow filtering of the web content arriving at a browser.

W3C's main thrust in this area is the Resource Description Framework (RDF) which is the language being developed to represent metadata. RDF has a key aim that it should be machine readable. It should allow an agent to make intelligent decisions based on the metadata it encounters.

Given an application domain, such as library cataloguing, there will be a need to define the domain vocabulary to be used (author, title etc). RDF does not itself define the vocabulary but provides a language to define vocabularies. Frequently, you may need to assemble metadata from more than one vocabulary (for example, a library catalogue and commercial data such as price). In consequence, RDF must be able to differentiate between metadata coming from different vocabularies.

The work in W3C has been split into two main parts:

The first W3C Recommendation will be the RDF Model and Syntax Specification. This came out as a Public Working Draft earlier in the year and there was a second Working Draft issued in August. Comments closed on 23 October, 1998 and it is anticipated that a Proposed Recommendation is imminent.

RDF is a way of defining the value of a property associated with a resource. So RDF can express statements like:

The value 3 is the violence rating of http://www.mad.com/

The property name is violence, the property value is 3 and the resource of the property is the web page in question. Resources do not have to be web pages; a resource could be a whole web site defined by a specific URL. You can even make statements about statements.

John Smith asserts that "The value 3 is the violence rating of the following web page".

Here asserts is the property, John Smith is the value and the previous statement is the resource.

And we don't have to stop there. You can have I believe that John Smith asserts that... and so on.

To write an RDF statement of this type, we need a syntax and, of course, XML is the syntax we use:

<RDF:Description
about= "http://www.mad.com" >
<PYC:violence> 3 </PYC:violence>
</RDF:Description>

Because we have properties that are part of RDF and properties defined for our example PYC rating, we need to differentiate between them, which is why the prefixes RDF: and PYC: appear. These naming conventions will be defined as part of the XML Namespace specification. Before the RDF statements above, we would need to specify where the RDF and PYC namespaces are defined.

We still have not given the meaning of the property violence nor any constraints that there may be on the property value (is 3 a number in the range 0 to 5 or in the range 1 to 10, say).

The aim of the RDF Schema Specification is to define the properties of a resource. It does not specify the vocabulary to be used. What it allows you to define is the vocabulary and the constraints to be put on the property values. To help in this it provides some basic datatypes and some resources and their properties (specified in the standard RDF Data Model).

<rdf:Description ID="violence" >
<rdfs:subClassOf resource="#PYCLabel" >
</rdfs:subClassOf>
<rdfs:range href="#Integer"></rdfs:range>
</rdf:Description>

The assumption here is that the core vocabulary for RDF schemas is defined in the rdfs namespace. This fragment specifies a property with name violence that is a subclass of the class PYCLabel defined elsewhere. The value of the property has to be an integer and we have not put any restrictions on its range of values. That would take quite a bit more RDF to achieve!

It is feasible that there will be several rating systems around for web pages and we may have another rating system which has aggression as a label in its label list. By having some idea of the meaning of violence and aggression in the two label lists, the possibility of translating between the two rating systems is enhanced.

While we are anticipating that the RDF Model and Syntax Specification will become a W3C Recommendation in the near future, it is likely that the move to Recommendation for the RDF Schema Specification may take a little longer.

New Members

Membership continues to rise and has now reached 289 with a regional break down of:

Full Affiliate
Americas 42 129
Europe 28 54
Asia-Oceania 16 20

Recent new members are:

RSA Event: 8 December 1998

Recent Web Developments and European industrial experience with them is the focus for the event to be held at the Royal Society of the Arts in London on Tuesday, 8 December 1998.

Jon Bosak, who chaired the W3C Working Group that developed the XML standard and currently chairs the W3C XML Coordination Group, is coming over just for this event. He is backed up by Tony Stewart of RivCom and Nic Fulton of Reuters describing how XML is being used by different industry sectors in Europe. RivCom will also be one of the demonstrators.

The new Scalable Vector Graphics Working Group is having a 2-day meeting in Bristol in November and Chris Lilley will be reporting on how that activity is developing. Three of the main players are committed to implementing the facilities so we should see at last the efficient production of graphics art and schematic images without having to resort to PNGs or GIFs.

Hakon Lie will be giving the current status of XSL and its relationship to CSS.

Michael Wilson, one of the architects of the Chameleon multimedia SMIL player and editor, will be giving an update on SMIL and David Bradshaw (BBC) will be reporting on the TV on the Web Working Group activities.

We are limited to about 150 people at RSA. Places are going quite fast so don't leave it to the last minute and be disappointed.

WWW8, 11-14 May 1999

Yes it is WWW Conference time coming around again. After the highly successful event in Brisbane, the location moves to Toronto for 1999 and the 8th event. The Conference is being held at the main Metro Toronto Convention Centre downtown. Bob Metcalfe is scheduled to give the final talk with his usual entertaining review of the Conference and the way forward. Greg Papadopoulos, the Chief Technology Officer at Sun, will be the opening speaker.

The main deadline at the moment is the Call for Papers which closes on 23 November 1998.

Style Sheets for HTML and XML by Frank Boumphey

Books arrive thick and fast these days. Boumphey's book has just arrived on the bookshelves. It is the first that attempts to describe XSL and CSS2 in relation to HTML and XML. Publishers are Wrox Press Inc. The XSL used is as defined in the May 1998 Working Draft so is not completely up-to-date but it does give a good overview of the whole area.

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