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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
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