Towards a semantic web

Philip Hider

This talkThe Semantic Web vision

Scenarios

Standards

Semantic Web & RDA

Web 1.0, 2.0, 3.0Internet to WWW (Web 1.0)Web 1.0 allows people to navigate the Internet

easily, through hyperlinks

Web 2.0 allows people to collaborate more on

the WebWeb 3.0 allows computers to find and use the

datacontained in Web documents

Web 3.0 = the Semantic Web vision

The Semantic Web visionIt will allow computers to make sense of the

content of Web documents, so that they can find and use this data independently

Basis of SW already developed, with standards such as XML and RDF

Like Web 1.0, it represents a bottom-up, distributed approach

How would it work?Computers would be able to identify and ‘understand’

particular data in a Web document according to the metadata associated with that data metadata could be inside our outside the document

Computers (agents) would then be able to relate that data to other data in other documents (or the same document) according to specified schemas, ontologies and rules

They could then independently integrate data and process information according to tasks set by their human users

A Semantic Web scenarioUser asks ‘Trip Agent’ to purchase the ‘best’

deal for a trip to New Zealand with date range x, family members y, time of day z, etc. etc.

‘Trip agent’ searches the Web for flights and accommodation, and is able to look up databases and specify conditions according to what it ‘knows’ about user’s preferences

Semantic Web scenarioAgent is able to ‘understand’ the deals

available on different websites by integrating data from different sources, e.g. looking up geographic information systems (how far from the sea, shops, etc.), weather forecasts, family members’ calendars, etc. an ultimately suggesting the optimal combination of flight, hotel, tours, etc.

Another scenarioUser asks if the latest Stephen King

book is available in a nearby library, can’t remember what it’s called

‘Library Agent’ searches the Web for nearby libraries with books by ‘Stephen King’, finds a few different Stephen Kings, confirms with user which Stephen King, then identifies the latest novel via the official Stephen King website, but chooses the second-nearest library (by car) which holds it because of availability/format/library opening hours, etc.

What do SW agents need?Information about the data, i.e. metadata,

in a machine-readable format

Including a shared understanding of the structure of that metadata and its relationship to other knowledge structures (ontologies)

Some clever programming

Standards for the Semantic WebResource Description Framework Universal Resource IdentifiersXMLUnicodeSchemas (such as XML schemas) Ontologies written in e.g. OWLRules written in RIF, etc.SPARQL

Resource Description FrameworkW3C standard

A model used to structure resource descriptions

Can be used to structure data about any kind of resource could be a book, or a car, or a flight ticket, or an

experiment, etc.

Based on ‘triples’, i.e.

Resource – Property – Value

(Subject – Predicate – Object)

Universal Resource Identifiers

For example, URLs

And ISBNs

People don’t have them yet

OCLC working on ‘work identifiers’

Properties and some values are referenced as

part of particular schemas, ontologies, etc.

eXtensible Markup Language (XML)

Another W3C standard

More flexible than HTML, XHTML

Can be used to encode any data

Data can be in the same Web document or another

document

Can be used to express RDF, i.e. RDF/XML

RDF/XML basis for metadata structures such as

schemas and ontologies

SchemasStandardised structures of resource

description that define property elements in a taxonomic way

Mostly based on a particular domain, e.g. pertaining to bibliographic data, or geospatial data, or flight booking data, or used car data, etc.

SchemasTwo main groups of schemas –

XML schemas and RDFS (RDF schemas)

Superseding Document Type Definitions (DTDs)

Specific well-known schemas includeDublin CoreONIXRSS

Some metadata encoded in RDF/XML

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:foaf="http://xmlns.com/foaf/0.1/" xmlns:dc="http://purl.org/dc/elements/1.1/"> <rdf:Description rdf:about="http://en.wikipedia.org/wiki/Tony_Benn"> <dc:title>Tony Benn</dc:title> <dc:publisher>Wikipedia</dc:publisher> <foaf:primaryTopic> <foaf:Person> <foaf:name>Tony Benn</foaf:name> </foaf:Person> </foaf:primaryTopic> </rdf:Description> </rdf:RDF>

Some metadata encoded in RDF/XML

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:foaf="http://xmlns.com/foaf/0.1/" xmlns:dc="http://purl.org/dc/elements/1.1/"> <rdf:Description rdf:about="http://en.wikipedia.org/wiki/Tony_Benn"> <dc:title>Tony Benn</dc:title> <dc:publisher>Wikipedia</dc:publisher> <foaf:primaryTopic> <foaf:Person> <foaf:name>Tony Benn</foaf:name> </foaf:Person> </foaf:primaryTopic> </rdf:Description> </rdf:RDF>

OntologiesMore sophisticated than schemas, formalising

more complex relationships between elementsAlso usually domain-specificUse extra languages, such as OWL, on top of

RDF/XML etc. Ontologies give more scope for agents to be

‘clever’Dublin Core can be expressed as an ontology

or a schema

What about MARC?MARC files are rather flat and do not readily

define relationships between elementsBut can be expressed as an XML schema,

i.e. MARCXMLMODS is a lite version of MARCXMLMappings between MARCXML and other

schemas (e.g. DC)

MappingsLots of them!

Between different schemas, ontologies,

languages, etc.

AKA crosswalks

By UKOLN, LC, OCLC, etc. etc.The more standards and adaptations, the

more crosswalks

Value setsResource – Property – Value

Schemas and ontologies may point to particular value sets, e.g.

Book A hasaSubjectcalled DCterms:LCSH Apples

where Apples is a value in the set of values known as LCSH

In other words, they may point to controlled vocabularies

SKOSSimple Knowledge Organization Systems

SW standard for expressing controlled

vocabularies such as subject thesauri

http://www.w3.org/2004/02/skos

Might promote use of LCSH, etc.

Semantic Web & cataloguingMore sophisticated use of library catalogues if

they can be understood by Semantic Web agents

Library resources more likely to be used in conjunction with non-library web resources

SW about agents using cataloguing, not replacing cataloguing

Semantic Web & RDARDA is therefore aligning itself with DC and

RDF

RDA elements mapped to DC, ONIX, etc.

DCMI/RDA Task Group

RDA-DC application profile

http://dublincore.org/dcmirdataskgroup

Prospects for SWExamples of Semantic Web developments:

http://www.w3.org/2001/sw/sweo/public/UseCases

A lot of standards now in place, technology not so much of an issue

With RDA, bibliographic domain ripe for SW take-up

Pre-SW library work

Post-SW library work

Thank you.

phider@csu.edu.au