1 Search and Navigate Web Ontologies Li Ding Tetherless World Constellation Rensselaer Polytechnic Institute Aug 22, 2008

2 Outline Background Enabling Search and Navigation Graph on Swoogle Enabling Collaborative Ontology Repository on Semantic Wikis

3 Online Ontology: Past and Future Pre-Web era (e.g. cyc, wordnet) –[semantics] define terms semantics, and interlink terms –[access] ontology available via local files, database, and KB Now (e.g. foaf) –Increasing adoption of semantic web languages –[access] published and shared on the Web Term identified by HTTP URI, support hyperlink Web 3.0 era (e.g. tw.rpi.edu) –Native semantic web support –[semantics] preserve provenance information (history, author) –[access] collaboratively maintained on Semantic Wiki Flexible ownership/edit granularity Dynamic update and growth In what follows, we focus on semantic web ontolgoies

4 SW Ontology: Conceptual Model wordNet:Agent rdf:type rdfs:Class rdfs:subClassOf foaf:Person foaf:mbox rdfs:domain rdf:type rdf:Property ex:Li foaf:mbox rdf:type foaf:Person class property SW Ontology Instance Data SW Document Meta Term t1 t2 t4 t3 foaf:mbox t5 t6 SW Term Usage Define class (t2) Define property (t4) Reference class (t1) Reference property (t3) Instantiate class (t5) Instantiate property (t6) Namespace instance

5 Enabling Search and Navigation Graph (SNG) on Swoogle Online ontology is not merely a web page, so users need effective means to access ontology at different levels of granularity.

6 Namespace SW Document SW Ontology hyperlink imports Term description 7 uses Search and Navigation Graph: Without Search Engine Both term and ontology are navigation stops Native semantic navigation (4,5,6,7), e.g. doc => term1 Native Web navigation (1,2,3), e.g. onto1.t1 => onto2.t2 Term lookup (match by name), e.g. fine concept person Meta Term 5 defines Term lookup string instantiates 4

7 Example: Browsing Ontology and Terms in Ontology Editor

8 What Else is Wanted? Better search interface –How do I find terms related to green tea –How do I find documents related to Li Ding More navigation paths –How to find instances of foaf:Person –How to find documents defining foaf:Person Utilizing instance data –What class is frequently used as the domain of dc:title ?

9 Example: Homepage of Term navigation paths Ranked description aggregationSurf to another term

10 Namespace SW Document SW Ontology defines hyperlink imports Term description 7 uses Search and Navigation Graph: Adding Keyword Search Semantically generate text metadata for term and ontology Keyword search (8,9), e.g. keywords => term Refined keyword search, e.g. prefix:keyword=> term Meta Term Term Search Document Search Keywords 8 9 lookup instantiates 4

11 Example: Term Search Ontology search: search for a collection of concepts Term search: search for one concept –Term search can support auto-completion via : label:agent More term search options: label: the lexeme of Term's local-name. e.g. 'SeaFood' has two labels: 'sea' and 'food' Keyword search Results ranked by popularity

12 Namespace SW Document SW Ontology defines hyperlink imports Term description, empirical relation 7 uses Search and Navigation Graph: Enriching Navigation Paths Use search engine metadata to improve navigation paths Inverse navigation path (4,5,7), e.g. namespace => term Empirical relation (6), e.g. dc:title => foaf:Person Meta Term Term Search Document Search Keywords 8 9 lookup 4 instantiate

13 Example: Query based navigation Navigate from class to documents containing instance data Query Docs By Term usage Meta usage

14 foaf:name rdfs:domain Onto 1 owl:Class rdf:type foaf:Agent rdfs:subClassOf Onto 2 dc:title rdf:type Dr. SWD3 foaf:Person foaf:name rdfs:domain foaf:Person owl:Class rdf:type foaf:Agent rdfs:subClassOf foaf:Person wob:hasInstanceDomain dc:title wob:hasInstanceDomain Tim Finin foaf:name Empirical Relations May not be defined in ontology, e.g. FOAF uses rdfs:seeAlso May be Inductively learned from instance data

15 Example: Empirical Navigation I-domain (p2c): the listed terms have been instantiated (by doc_freq semantic web documents) as the domain of the specified term

16 Summary: Enabling Search and Navigation Graph in Swoogle Key technologies –Keyword search – natural language UI –Query based navigation – enrich navigation path –Ranking – promote reuse –Provenance – Each SNG node has an aggregated homepage, enable global view –Version cache – ensure permanency Implementation highlights –19 REST web services, implemented as JAVA servlet, outputs are in encoded in RDF (using WOB and SWOOGLE ontology)19 REST web services –Web interface ( implemented using PHP, provide HTML interface for access web services and retrieve query resultshttp://swoogle.umbc.edu

17 Enabling Collaborative Ontology Repository on Semantic Wikis Interestingly enough, the search and navigation graph (SNG) nicely fits the structure of Semantic Wikis

18 Authoring Ontologies on Semantic Wiki Wiki natively supports –Collaborative edit: user login, online editing –Provenance tracking: revision history, authors –Navigation: wiki-link, external-link, what links here Semantic Wiki supports –HTML and RDF homepage for each term (class, property, instance) and ontology –RDFS inference, and potentially some OWL inference –Allow coexistence of ontology and instance –Conventional ontology editing UI via (i) template or (ii) semantic form + auto-completion

19 Highlight 1: Wiki Homepage for Each Term and Ontology (SNG node)

20 Highlight 2: Provenance Preserving Concept Convergence Concept Convergence –One latest revision –Multiple authors –Dynamic concept may have many revisions –Stable concept may be Protected Provenance in history –Author –Change date –Changed content –Change notes

21 Highlight 3: Supporting Multiple Ontologies Concpets from different ontologies may stay together and be connected

22 Summary: Enabling Collaborative ontology repository on Semantic Wikis Key technologies evaluation –Concept modeling – capable of RDFS, OWL, OBO storage –Keyword search - wiki native search is not enough –Navigation – absorb Swoogle technology –Ranking – absorb Swoogle technology –Provenance – add semantic history Implementation highlights – is an experimental work, which develops ontology for annotating instanceshttp://tw.rpi.edu/ –Semantic Mediawiki (SMW) and a selection of SMW extensions as the infrastructure –A set of wiki templates and semantic forms (in form of special wiki pages) for improving user interface