1. RDF
David R Newman
15 July 2009

2. Overview RDF Generation Ontology Design SPARQL Endpoint
OAI-ORE Export & Research Objects
Linked Data
Why Bother?
RDF Generation
Ontology Design
SPARQL Endpoint
OAI-ORE Export & Research Objects
Why Bother?

3. RDF Generation - Issues
Don’t want to expose all database data
Irrelevant
Secret
Private
Rationalisation of data
Link up data
Reuse data properties
Greater / more logical abstraction
Don’t want to expose all database data
Irrelevant – plugin schema and oauth tables
Secret – Crypted password and salt, reset password code, remember tokens, oauth tables
Private – Contributions, open_id, regsitered account
Rationalisation of data
Link up data – Bits of the same object in different SQL tables, multiple sql fields into single RDF property
Reuse data properties – map sql fields to pre-defined RDF properties
Greater / more logical abstraction – Database has evolved and is strongly tied to the web interface. The logical model is different and can and should be more consistent and structured.

4. RDF Generation - Implementation
Bespoke SQL queries
Simple mapping language
URIs
Resolves to RDF/XML representation
Protecting private data
401 authorization required
Authorization credentials stored in session
Bespoke SQL queries – Join up tables so can generate all properties of an object. Restrict the records that are selected dependent on domain, private/public/protected
Simple mapping language – Map fields to RDF property directly, map multiple fields to compound property, use a function to munge data for formatting or representing the data more logical. E.g. Working out who is the requester and accepter for a Friendship/Membership
URIs
Resolves to RDF/XML representation
- Are these URIs right. Should we use content resolution and use same URIs as web interface
Protecting private data
401 authorization required
Authorization credentials stored in session

5. RDF Example
<mebase:Group rdf:about=" <mebase:human-start-page rdf:resource=" <sioc:has_owner rdf:resource=" <dcterms:created rdf:datatype=" T17:02:58Z </dcterms:created> <dcterms:modified rdf:datatype=" T09:53:02Z </dcterms:modified> <sioc:name rdf:datatype=" myExperiment </sioc:name> <dcterms:description rdf:datatype=" <p>This is the official group for the myExperiment team</p> </dcterms:description> <mebase:auto-accept rdf:datatype=" 0 </mebase:auto-accept> </mebase:Group>
Example of a Group in RDF/XML
Had to map networks in SQL to Group in RDF
Adding RDF URI domain to user_id for group owner
Dates needed to be reformatted
Description needs to xml entity escaped to produce valid xml
Datatypes specified – automatically pulled in from the ontology. External properties defined manually

6. Ontology Design http://rdf.myexperiment.org/ontologies/
Reuses properties and extends classes
From Dublin Core, SIOC, FOAF, OAI-ORE and Creative Commons
Modularized
Reuses properties and extends classes
From Dublin Core, SIOC, FOAF, OAI-ORE and Creative Commons
Modularized
- SNARM for policies/permissions
- Base – Users/Groups, abstract Contribution/Annotation class. Friendships, Memberships, Invitations and Messages
- Annotations and Contributions – specific types
- Viewings & Downloads, Attribution & Creditation, Packs and Experiments are fairly obvious to what they are
- Components for Workflows. Designed for Taverna but is quite generic
- Specific Imports all the modules and pull things together as well as providing classes/instances specific to myExperiment

7. SPARQL Endpoint Public RDF/XML imported to JENA triplestore
PHP hooks provide web interface
Public RDF/XML imported to JENA triplestore
PHP hooks provide web interface

8. OAI-ORE Export & Research Objects
For Packs and Experiments
303 redirects dependent on HTTP accept value
application/rdf+xml -> RDF resource map
application/atom+xml -> Atom entry
text/html -> splash page
Atom Feeds
Build on OAI-ORE Export for Research Objects
For Packs and Experiments
303 redirects dependent on HTTP accept value
application/rdf+xml -> RDF resource map
application/atom+xml -> Atom entry
text/html -> splash page
Atom Feeds
Build on OAI-ORE Export for Research Objects – Has helped to inform the design of ROs

9. Linked Data Hash URIs or 303 Redirects
303 Redirects from the Mothership
303 Redirects designed for content resolution
Current design more suited to 303 redirects
RDF “Links”
Need to be linked to/from a project already part of the Linked Data Project (e.g. RKBExplorer, Eprints, etc.)
Minimum 100 links required

10. Why Bother? RDF is a standard format Generic rather than structured
SPARQL allows flexible queries
Align termininology with other projects
Inference
RDF is a standard format - Other people are using it and lots of tools out there to consume it
Generic rather than structured - Allows easy adaptation when new data needs to be represented
SPARQL allows flexible queries - A querying interface that allows users great flexibility to what they can query
Align termininology with other projects - Makes data interchange easier
Inference – Get more for less