© 2006 Hewlett-Packard Development Company, L.P.The information contained herein is subject to change without notice

Use Case:Populating Business Objects

W3C Workshop on RDF Access to Relational Databases

Andy Seaborne (HP), Damian Steer (ILRT)

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Business Problem• New business process• XML objects• Data in various places

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Technical Problem

? ? ?

Geographic Production

<?xml>… <site> <location>??</location> <name>??</name> <capacity>??</capacity> <history> . . . </history> </site>…

Asset & History

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Technical Approach

Single SPARQL Query

Translation between domains

Databases Databases Databases

SquirrelRDF

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SquirrelRDF• http://jena.sf.net/SquirrelRDF• SPARQL to SQL

−And LDAP and IMAP

• RDB Mapper−(c.f. TimBL’s Design note)

• Simple servlet• Results in SPARQL XML Results Format,

JSON, …• … and RDF.

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RDB Mapper

• Automatic Generation• A map is a number of mapped classes

−Not necessarily in the same database

ex:map a db:Map ; db:mapsClass ex:People , ex:Department .

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RDB Mapper : Classes

• Tables map to classes

ex:People a rdfs:Class ;

db:primaryKey ex:propA ;

db:database <jdbc:mysql://localhost/conference> ;

db:table “People" .

CREATE TABLE People ( id int, name varchar(30), PRIMARY KEY id )

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RDB Mapper : Properties

ex:people_id a rdf:Property ; rdfs:domain ex:people ; db:col "id" ; db:colType "int" .

ex:people_name a rdf:Property ; rdfs:domain ex:people ; db:col "name" ; db:colType "varchar" .

CREATE TABLE People ( id int, name varchar(30), PRIMARY KEY id )

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SquirrelRDF• Hard: SPARQL patterns with a property

variable−{ <id1234> ?p “foo” }

• Hard: Query over types−{ ?s rdf:type ?type }

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Rules• SPARQL basic graph pattern

−point at which data is accessed in SPARQL

• BGP translation−SPARQL pattern match => calculate =>

generate pattern

−Generate pattern more than a BGP (e.g. UNION)

• Applied to query coming in• Targeting databases left to SquirrelRDF

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Rules Used • Used

−Reformat a key

−Property => property

−Join across databases by key

−Multiple places for one value

• Notes−In this use case, no rewriting the query results

was necessary, but likely needed in other situations.

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Summary

• Domain mapping problem is not SQL specific

− SPARQL-rewrite rules encapsulate mapping

• Direct database encapsulation− Scale, maintenance

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Jena extended tools family

External bridges

GlozeXML

XML Schema

RDF

OWL

GRDDLXML

with GRDDL annotation

RDF

SquirrelRDFRDF

SPARQLRDBMS

LDAP

JosekiRDF Server

DARQdistributed

SPARQL query

Access

PortalCoreFacetted browse

Brownsauce

RDF explorer

UI

Tools

EyeballConfigurable

RDF validator

Jena Ontology API

SPARQL API

query & update

RDF API

RulesExterna

lNone

Inference

Writers

RDF/XMLN3

TurtleN-triple

Readers

RDF/XMLN3

TurtleN-triple

Graph and query (Store SPI)

MemoryFile

backed SDBSPARQL

database

RDB

Command line tools

- merge RDF- convert format

- schemagen- db load

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Example: Semantic Web Environmental Directory

www.swed.org.uk

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Example: Seeker – an Education Portal for the Singapore Government