Semantic Web tools and applications

Libby Miller

Presentation at SWeb Forum 2004, 30 November 2004 at La Trobe University, Bundoora, Victoria

Overview

Introduction: SWAD-Europe, RDF and developers
Semantic Web working groups at W3C
Querying and the DAWG
Semantic Web Best Practices
Applications and Demos: FOAF, DOAP, SWED portal and image annotation

Semantic Web, developers, and SWAD-Europe

3-4 years ago RDF looking weak, not getting traction with XML developers
SWAD-Europe project - take a developer-orientated perspective on the Semantic Web
Demonstrators, fundamental software, pre-standardization work, answering developer FAQs, being available online to answer questions

RDF and OWL

RDF is things and their relationships, using URIs to identify things and their attributes
RDFS has weak mechanisms for describing class hierarchies, with URIs identifying (sub)classes and (sub)properties
OWL can give more precision to these hierarchies and has other useful features
None of these are much good for validation in an XML sense

What's so great about the Semantic Web?

Makes some implicit information explicit
Provides linking mechanisms for data and schemas - enables linking of heterogeneous and distributed data and schemas
Hammer in search of nails: hence the importance of applications and demonstrators

W3C Semantic Web working groups

RDF Core - finished: strengthening and clarifying RDF; testcases and firm logical foundation; stopping arguments
WebONT (OWL) - finished: and gaining in use, although less often in its Description Logic form
DAWG - in progress: query usecsaes and requirements; SPARQL
SWBP - in progress: "to provide hands-on support for developers of Semantic Web applications"

RDF Query and the DAWG

Querying RDF is hard with XML tools, because RDF is a graph encoded as a tree
Being able to query RDF is essential for building applications
Most toolkits have an SQL-ish query language

SPARQL example


PREFIX foaf:    
SELECT * WHERE 	( ?x foaf:name ?name )
		( ?x foaf:mbox ?mbox )

Some query and storage tools

Jena (Java, HP Labs)
Redland (C, Dave Beckett, ILRT)
Sesame (Java, Aduna)

all are Open Source and well-supported. Many more are available.

Semantic Web Best Practices WG

aim: "to provide hands-on support for developers of Semantic Web applications"

Chartered for 20 months from March 2004
Small taskforces working on different tasks

SWBP Taskforces

Ontology Engineering and Patterns "document common and reusable ontology patterns, and general ontology engineering best practices"
RDF/Topic maps interoperability Produce guidelines for transforming a topic map into an RDF/OWL representation and vice versa.
XML Schema Datatypes and Semantic Web Answering difficult questions about the relationship between XML schema and RDF

Thesauri TF

Providing mechanisms to move from thesauri, which are very useful but also imprecise (part of and subclass of, isa) to ontologies with subclass structure.
Currently work is focussed on transforming existing thesuari to RDF form. Lots of interest among the digital libraries community. Substantial community working in this area now (Alistair Miles/SWAD-E).

Wordnet TF

"guidelines for transforming existing wordnets into an RDF/OWL representation"

Issue here is whether to treat these lexical data sources as about words or about things. Some similarity with thesauri. Incredibly useful.

HTML and RDF TF

Embedding RDF in HTML
Currently a subset of RDF can be put in the header of an HTML document; or linked to from the head; or embedded somewhere within the document, possibly in a comment.
meta approach is limited
embedding doesn't allow validation and in comments is horrible
linking is awkward for authoring tools
current proposals: a new syntax for RDF for XHTML2 and GRDDL

Vocabulary Management TF

"To point to and briefly summarize ongoing the evolving diversity of practices and approaches to declaring and managing vocabularies"

Turns out developing, combining and maintaining vocabularies is not straightforward
Tom Baker from Dublin Core leading

Applications and Demos TF

"to create a list of existing Semantic Web applications and demos" Trying to use SW tools and techniques to create and manage this data

Apps and demos: SWED

A demo from SWAD-Europe by HP Labs
Distributed data creation, harvesting
Facetted browsing using thesauri

Reusing SWED for Apps and demos

SWED can be customised to different kinds of data, for example DOAP (Description Of A Project)
For the apps and demos TF, we have customised SWED to use DOAP

Apps and demos: FOAF and FOAF tools

FOAF is Friend of a Friend: a vocabulary for describing people; a community; a fun thing
many applications, including foaf-a-matic; foafnaut; foaf explorer are some tools that are available

Apps and Demos: Image Annotation

Various applications for image annotation, from snapshot to more detailed work
Mindswap, Tidepool, Jim Ley's SVG annotation tool, Masahide Kanzaki's tool; SWAD-Europe javascript tool

and finally...

I hope I've shown some of the tools, applications and demos available
There's also a thriving developer community based around the Semantic Web Interest Group mailing list and IRC channel
This presentation + links are at http://swordfish.rdfweb.org/discovery/2004/11/webforum/

References / URLs

Toolkits:

C: Redland http://librdf.org/

Java: Jena2: http://www.hpl.hp.com/semweb/
Sesame: http://www.openrdf.org/

PHP: RAP: http://www.wiwiss.fu-berlin.de/suhl/bizer/rdfapi/
ARC: http://www.appmosphere.com/pages/en-arc

see also RDF resource guide: http://www.ilrt.bris.ac.uk/discovery/rdf/resources/

Working Groups

DAWG (Data Access) - RDF Query: http://www.w3.org/2001/sw/DataAccess/

SWBP (Best Practices) http://www.w3.org/2001/sw/BestPractices/

RDF/HTML mailing list: http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/

RDF in XHTML proposal: http://www.w3.org/MarkUp/2004/02/xhtml-rdf

GRDDL: http://www.w3.org/2004/01/rdxh/spec

Thesaurus mailing list: http://lists.w3.org/Archives/Public/public-esw-thes/

Applications and demos: http://esw.w3.org/mt/esw/archives/cat_applications_and_demos.html

Specifications:

RDF/RDFS - see list on http://www.w3.org/RDF/

OWL - http://www.w3.org/2004/OWL/

SWAD-Europe

Recent article about the project: http://www.ercim.org/publication/Ercim_News/enw59/brickley.html

Main site: http://www.w3.org/2001/sw/Europe/

Thesaurus site: http://www.w3.org/2001/sw/Europe/reports/thes/

Weblog (now used for thesauri and apps and demos): http://esw.w3.org/mt/esw/

Wiki (used in the community): http://esw.w3.org/topic/FrontPage

Community resources

SWIG (Semantic Web interest Group) homepage: http://www.w3.org/2001/sw/interest/

IRC channel: irc.freenode.net #swig Collaborative weblog: http://swig.xmlhack.com/

Planet RDF: http://planetrdf.com/

ESW wiki: http://esw.w3.org/topic/FrontPage

SWIG mailing list: http://lists.w3.org/Archives/Public/www-rdf-interest/

FOAF mailing list: http://rdfweb.org/mailman/listinfo/rdfweb-dev

Applications and Demos

SWED: http://www.swed.org.uk/

FOAF: http://www.foaf-project.org/

FOAF Explorer: http://xml.mfd-consult.dk/foaf/explorer/

FOAFNaut: http://blub.foafnaut.org/, http://www.foafnaut.org/

foaf-a-matic: http://www.ldodds.com/foaf/foaf-a-matic.html

DOAP: http://usefulinc.com/doap

doap-a-matic: http://doapy.bonjourlesmouettes.org/doap-a-matic

Image annotation by Masahide Kanzaki: http://www.kanzaki.com/docs/sw/img-annotator.html

SWAD-Europe javascript image annotation tool: http://swordfish.rdfweb.org/discovery/2004/03/w3photo/annotate.html