Employing RDFa for Collaborative Knowledge Engineering

Sebastian Tramp, Norman Heino, Sören Auer, Philipp Frischmuth

Agile Knowledge Engineering and Semantic Web (AKSW) – Universität Leipzig

• HTML forms are unaware of semantics

• HTML5 allows pre-defined input state semantics

• Sophisticated user support requires definable semantics!

on the Web

Knowledge Engineering

Currently: hard-wired semantics, abuse of class attributes

RDFa

• Annotating XML documents with RDF

• Human and machine-readable

• MVC – declare view in model language

Images: http://www.w3.org/TR/xhtml-rdfa-primer/

Knowledge Engineering

• RDFa page, updatable knowledge store

• "Intelligent" editing components (widgets)

• Supporting the user

by Employing RDFa

XHTML+

RDFaWeb

Server+

RDF Store

Edit

SPARQL/Update

HTTP

Requirements

• Editing data chunks

• Standards-based update

• Light-weight addition

• Extensible widget pool

• Multiple sources

for RDFauthor

Named Graphs and Provenance

• Data source for each triple

• Update endpoint (SPARQL/Update)

• Query endpoint for reference (SPARQL)

Extending RDFa

<p about="http://sebastian.tramp.name" typeof="foaf:Person"> <img rel="foaf:depiction" src="http://aksw.org/img/…" /> <strong property="foaf:name">Sebastian Tramp</strong> </p>

RDFa Example

<p about="http://sebastian.tramp.name" typeof="foaf:Person"> <img rel="foaf:depiction" src="http://aksw.org/img/…" /> <strong property="foaf:name">Sebastian Tramp</strong> </p>

<p about="http://www2009.eprints.org/63/1/p621.pdf" typeof="foaf:Document"> <span property="dc:description">…</span> Author: <span rel="foaf:maker" resource="http://sebastian.tramp.name">…</span> </p>

RDFa Examplefrom Two Sources

RDFa Example

http://buzzword.org.uk/2009/rdfa4/spec

with Named Graphs

<div update:from="http://showcase.ontowiki.net/"> <p about="http://sebastian.tramp.name" typeof="foaf:Person"> <img rel="foaf:depiction" src="http://aksw.org/img/…" /> <strong property="foaf:name">Sebastian Tramp</strong> </p></div><div update:from="http://publications.aksw.org"> <p about="http://www2009.eprints.org/63/1/p621.pdf" typeof="foaf:Document"> <span property="dc:description">…</span> Author: <span rel="foaf:maker" resource="http://sebastian.tramp.name">…</span> </p></div>

<link about="http://showcase.ontowiki.net/" rel="update:updateEndpoint" href="http://trunk.ontowiki.net/sparql/" />

<link about="http://showcase.ontowiki.net/" rel="update:updateEndpoint" href="http://trunk.ontowiki.net/sparql/" />

Provenance

@prefix update: <http://ns.aksw.org/update/> .

Implementation

HTML Form• Widget selection/form creation

RDF Store

• Update propagation

Extracted Triples

• Client-side page processing XHTML

+RDFa

• Page creation

System Architecture

W3C RDFa parser2 (+NG)rdfQuery1

RDFauthor3

1http://code.google.com/p/rdfquery/2http://www.w3.org/2006/07/SWD/RDFa/impl/js/3http://code.google.com/p/rdfauthor/

Widgets

• Semantics-aware

• Hide confusing options by default

• One widget edits one statement's object

• Register for widget hooks

Widget Hooks

Hook name Hook value (example)

subject URI http://id.feedface.de/me

rdfs:range of predicate rdfs:Literal

rdfs:Datatype of object xsd:string

predicate URI http://xmlns.com/foaf/0.1/name

rdf:type of object rdfs:Literal

Widgets (contd.)

xsd:date

rdf:Resource

Overlay Form

• Structure-agnostic

• Widgets can be grouped by predicate

• Decelerated workflow

Inline Form

• Seamless integration

• Form layout follows markup structure

• Structure-aware

• Problems with certain RDFa features

Update Propagation

• Widgets update graphs

• Calculate diff graphs

• Sent via SPARQL/Update to each source

RDF Store

Use Casesand Evaluation

OntoWiki

Wiki Pages

Wiki Pages (contd.)

Data Collection

Data Collection (contd.)

Conclusions

• RDFauthor allows to create editable semantic mashups

• Shields the user from RDF model intricacies

• Minimal impact on the web page being edited

Demo Session

Wednesday, 4 – 6pm, Room 2

… or anytime