Joining the Semantic Web: a Practical Guide

n Joining the Semantic Web: a Practical Guide.

Pasqualino “Titto” AssiniPasqualino “Titto” AssiniNesstar Ltd - UKNesstar Ltd - UK

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NESSTAR : The “Data Web”NESSTAR : The “Data Web”

• The Data Web is the application of Semantic Web techniques and principles to the problem of statistical data and metadata (surveys, opinions polls) dissemination and processing.


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Joining the Semantic Web in A Few Easy(?) Steps

• Know What You Want To Say Modelling

• Then Say It -> Map the Model to a Semantic Web Language

• Think of the Future Managing Change

• Let Everybody Know Publishing on the Semantic Web

• Make Your Entities Behave Specifying Operations/Services


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Additional Considerations

• Keep it Simple Or Else Why Being Too Clever Doesn’t Work on the Internet.

• XML – Friend or Foe of the Semantic Web?


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Know What You Want To Say

• The Semantic Web is no silver bullet. It won’t help you in modelling your data.

• Use your existing modelling language (and models).

• You can also use RDF/RDF Schema but:– Not many (graphical tools) tools – Not much expressive power (example: no

relationships)

• Tip: Use standard UML design tools (in most cases a UML Class Diagram is all you need)


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Now Say It

• Once you have you model you need to translate it to a Semantic Web Language:– Choose the target language: RDF, WOL– Define the mapping rules (might be already

defined, UML RDF)

• What about using a specialised XML syntax? – Advantage: More compact/simpler syntax– Disadvantage: Difficult to design properly, need to

define an additional mapping to RDF.

• Tip: Stick to standard RDF syntax.


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Managing Change

• Fact of Life: things change, models do as well.

• Specific Application/Clients will need to extend your core model.

• Good News: RDF was custom made to be extensible (class/property inheritance, additional properties, reification)

• Tip: Make sure that your applications can handle model extensions.


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Publishing on the Semantic Web

• Wrong assumption: You need something special, a Registry maybe (e.g, UDDI)

• This can be real easy, just do it the WWW way.

• Self-description principle: objects and types self-describe themselves by making accessible, via HTTP, their RDF description at their URL.


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Specifying Specifying Behaviour• Example: Bank Account operations to pay in or

draw money.

• The Semantic Web is silent on this point.

• Major oversight Web Services come to the rescue.

• Problem: Web Services and the Semantic Web are not well integrated (but we might soon have an RDF model of WSDL).

• Can’t wait? Use what is available: DAML-S, NEOOM (simple RDF model of methods plus method invocation via HTML FORMs).


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Keep It Simple or Else• Fact: The value of an information

dissemination system depends on the quantity of information it contains and the number of eyeballs looking at it.

• Therefore: initially the system is worthless (the Web was, the Semantic Web still is).

• But, if it starts growing it can grow real fast.

• So: how do you get the snowball going? KISS to lure early adopters.


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XML - Friend of Foe ?• (RDF/)XML is very hard to write by hand and not

particularly pleasant to read.

• It would be very useful if people (early adopters) could jot down semantic web descriptions without tools (think of HTML).

• TBL has lately engaged in an unofficial and very politically incorrect activity: defining a non-XML syntax for RDF: N3.

• What about an official W3C initiative to create a semantic web language that is not only machine understandable but also easy for an human to read and write?

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Joining the Semantic Web: a Practical Guide