joshua scotton [email protected] owl-ql
TRANSCRIPT
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OWL-QL
• OWL Query Language)
• Based on DQL (DAML Query Lang.)
• Simple Request-Response Model• http://www-ksl.stanford.edu/projects/owl-ql/
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Basic Queries
1. a query pattern (required)
2. a must-bind variables list
3. a may-bind variables list
4. a don’t bind variables list
5. an answer pattern
6. a query premise
7. an answer KB pattern
8. an answer bundle size bound
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A simple OWL-QL query
If C1 is a Seafood Course and W1 is a drink of C1, what color is W1?
P: (type C1 Seafood-Course) (drink C1 W1)
Q: (has-color W1 ?x)
V: must-bind ?x
AP: drink ?x Wine with Seafoood
KB: http://somewhere.com/wine.owl
A: drink White Wine with Seafood
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A Simple OWL-QL QueryThe following is the actual query:<owl-ql:query xmlns:owl-ql="http://www.w3.org/2003/10/owl-ql-syntax#" xmlns:var="http://www.w3.org/2003/10/owl-ql-
variables#" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:owl="http://www.w3.org/2002/07/owl#">
<owl-ql:premise> <rdf:RDF> <rdf:Description rdf:about="#C1">
<rdf:type rdf:resource="#Seafood-Course"/>
<drink rdf:resource="#W1"/>
</rdf:Description> </rdf:RDF></owl-ql:premise>
<owl-ql:queryPattern> <rdf:RDF> <rdf:Description rdf:about="#W1">
<has-color rdf:resource="http://www.w3.org/2003/10/owl-ql-variables#x"/>
</rdf:Description> </rdf:RDF> </owl-ql:queryPattern>
<owl-ql:mustBindVars> <var:x/> </owl-ql:mustBindVars>
<owl-ql:answerKBPattern> <owl-ql:kbRef rdf:resource="http://ontolingua.stanford.edu/wines.owl"/> </owl-ql:answerKBPattern>
<owl-ql:answerSizeBound>5</owl-ql:answerSizeBound>
</owl-ql:query>
This would normally be included inside a SOAP message
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Response to Simple Query
<rdfs:Class rdf:ID="SEAFOOD-COURSE"> <owl:subClassOf> <owl:Restriction>
<owl:onProperty rdf:resource="#DRINK"/> <owl:toClass> <owl:Restriction>
<owl:onProperty rdf:resource="#COLOR"/> <owl:hasValue rdf:resource="#WHITE"/>
</owl:Restriction> </owl:toClass>
</owl:Restriction> </owl:subClassOf>
</rdfs:Class>
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Query patterns
• specifies a collection of OWL sentences in which some URI refs are considered to be variables
• Query Pattern: (owns ?p ?c) (type ?c Car) (has-color ?c Red)
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OWL-QL bindingsThree types of OWL-QL bindings
1. must-bind variables listsAnswers must provide bindings for all the must-bind variables
2. may-bind variables listsAnswers may provide bindings for any of the may-bind variables
3. don’t-bind variables listsAnswers are not to provide bindings for any of the don’t-bind variables
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OWL-QL bindings• A KB may entail the existence of a query answer,
but not entail a binding for every variable in the query
• A KB says-every person has exactly one father and - Joe is a person
• The KB-entails that Joe has a father-but may not entail a value of property “hasFather” for Joe(i.e., the KB may not identify the father)
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Another Query
Who owns a red car?
Query Pattern: (owns ?p ?c) (type ?c Car) (has-color ?c Red)
Must-Bind Variable: ?pDon’t-Bind Variable: ?cAnswer Pattern: owns ?p a red car
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Answer patterns
• specify the format in which answer bindings are returned
• Answer Pattern: owns ?p a red car
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Query Premises• “if-then” queries cannot be stated using only a query
pattern• When a premise is included in a query it is considered to
be included in the answer KB
Query: “If C1 is a Seafood Course and W1 is a drink of C1, then what color is W1?
Premise: (type C1 Seafood-Course) (has-drink W1 C1)Query Pattern: has-color W1 ?xMust-Bind Variables: ?x
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Answer KB patterns
• The Answer KB is a set of OWL sentences that are used by the server in answering the query
• If a query’s answer KB pattern is a variable then the server is free to select or to generate an answer KB from which to answer the query.
• If a query’s answer KB pattern is a list of KBs then answer sentences must be entailed by conjunction of the KBs in that list
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Answer bundle size bounds
• specify the maximum number of answers in each “bundle”
• answers are delivered by the server in bundles
<owl-ql:answerSizeBound>5</owl-ql:answerSizeBound>
• contain at most the number of query answers given by the answer bundle size bound
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The Car Query<owl-ql:query xmlns:owl-ql="http://www.w3.org/2003/10/owl-ql-syntax#"
xmlns:var="http://www.w3.org/2003/10/owl-ql-variables#">
<owl-ql:queryPattern><rdf:RDF> <rdf:Description rdf:about="http://www.w3.org/2003/10/owl-ql-variables#p"> <owns rdf:resource="http://www.w3.org/2003/10/owl-ql-variables#c"/> </rdf:Description> <Car rdf:ID="http://www.w3.org/2003/10/owl-ql-variables#c"> <has-color rdf:resource="#Red"/> </Car></rdf:RDF></owl-ql:queryPattern>
<owl-ql:mustBindVars><var:p/></owl-ql:mustBindVars> <owl-ql:answerKBPattern><owl-ql:kbRef
rdf:resource="http://joedata/joe.owl"/></owl-ql:answerKBPattern><owl-ql:answerSizeBound>5</owl-ql:answerSizeBound>
</owl-ql:query>
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An OWL-QL answer
Contains:
• answer pattern instances
• an answer bundle
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The Car Query Answer<owl-ql:answerBundle xmlns:owl-ql="http://www.w3.org/2003/10/owl-ql-syntax#"
xmlns:var="http://www.w3.org/2003/10/owl-ql-variables#">
<owl-ql:queryPattern><rdf:RDF> <rdf:Description rdf:about="http://www.w3.org/2003/10/owl-ql-variables#p"> <owns rdf:resource="http://www.w3.org/2003/10/owl-ql-variables#c"/> </rdf:Description> <Car rdf:ID="http://www.w3.org/2003/10/owl-ql-variables#c"> <has-color rdf:resource="#Red"/> </Car></rdf:RDF></owl-ql:queryPattern>
<owl-ql:answer> <owl-ql:binding-set> <var:p rdf:resource="#Joe"/> </owl-ql:binding-set> <owl-ql:answerPatternInstance> <rdf:RDF> <rdf:Description rdf:about="#Joe"> <owns rdf:resource="http://www.w3.org/2003/10/owl-ql-variables#c"/> </rdf:Description> <Car rdf:ID="http://www.w3.org/2003/10/owl-ql-variables#c"><has-color rdf:resource="#Red"/></Car> </rdf:RDF> </owl-ql:answer>
<owl-ql:continuation> <owl-ql:none/> </owl-ql:continuation> </owl-ql:answerBundle>
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Online Demonstrations
• Try OWL-QL Query Service at http://onto.stanford.edu:8080/owql/FrontEnd
Questions?
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