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Search and Navigate Web Ontologies

Li DingTetherless World Constellation

Rensselaer Polytechnic Institute

Aug 22, 2008

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Outline

• Background

• Enabling Search and Navigation Graph on Swoogle

• Enabling Collaborative Ontology Repository on Semantic Wikis

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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

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SW Ontology: Conceptual Model

wordNet:Agent

rdf:typerdfs:Class

rdfs:subClassOf

foaf:Person

http://xmlns.com/foaf/0.1/index.rdf

foaf:mbox

rdfs:domain

rdf:typerdf:Property

ex:Li

foaf:mbox

rdf:type

dingl@cs.rpi.edu

foaf:Person

http://www.cs.rpi.edu/~dingl/foaf.rdf

class

property

SW Ontology

Instance Data

SW DocumentMeta 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

http://xmlns.com/foaf/0.1/

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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.

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Namespace

SW DocumentSW Ontology

1 2

6

3

hyperlink

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

instantiates4

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Example: Browsing Ontology and Terms in Ontology Editor

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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 ?

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Example: Homepage of Termnavigation paths Ranked description aggregation Surf to another term

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Namespace

SW DocumentSW Ontology

1 2

6

35 defines

hyperlink

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

Keyw

ords

8

9

lookupinstantiates4

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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: http://swoogle.umbc.edu/index.php?option=com_swoogle_manual&manual=search_swt label:  the lexeme of Term's local-name. e.g.  'SeaFood' has two labels: 'sea' and 'food'

Keywordsearch

Resultsranked bypopularity

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Namespace

SW DocumentSW Ontology

1 2

6

35 defines

hyperlink

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

Keyw

ords

8

9

lookup4 instantiate

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Example: Query based navigation

• Navigate from class to documents containing instance data

Query Docs By Term usage

Meta usage

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foaf:name rdfs:domain

Onto 1

owl:Classrdf:type

foaf:Agentrdfs:subClassOf

Onto 2

dc:titlerdf:type

Dr.

SWD3

foaf:Person

foaf:Person

foaf:namerdfs:domain

foaf:Person

owl:Classrdf:type

foaf:Agentrdfs:subClassOf

foaf:Person

wob:hasInstanceDomain

dc:title

wob:hasInstanceDomain

Tim Fininfoaf:name

Empirical Relations• May not be defined in ontology, e.g. FOAF uses rdfs:seeAlso• May be Inductively learned from instance data

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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 http://webns.net/mvcb/generatorAgent

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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)– Web interface (http://swoogle.umbc.edu), implemented using

PHP, provide HTML interface for access web services and retrieve query results

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Enabling Collaborative Ontology Repository on Semantic Wikis

Interestingly enough, the search and navigation graph (SNG) nicely fits

the structure of Semantic Wikis

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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

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

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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

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Highlight 3: Supporting Multiple Ontologies

• Concpets from different ontologies may stay together and be connected

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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– http://tw.rpi.edu/ is an experimental work, which develops

ontology for annotating instances– 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