Ontology Query

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Ontology Query
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What Is Ontology

• Ontologies resemble faceted taxonomies but use
  richer semantic relationships among terms and
  attributes, as well as strict rules about how to
  specify terms and relationships. Because
  ontologies do more than just control a
  vocabulary, they are thought of as knowledge
  representation. The oft-quoted definition of
  ontology is "the specification of one's
  conceptualization of a knowledge domain."
• iawiki.net/IAGlossary

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Some Related Languages For Web Ontology

• XML provides a surface syntax for structured
  documents, but imposes no semantic constraints on
  the meaning of these documents.
• XML Schema is a language for restricting the
  structure of XML documents and also extends XML
  with data types.
• RDF is a data model for objects ("resources") and
  relations between them, provides a simple
  semantics for this data model, and these data
  models can be represented in an XML syntax.
• RDF Schema is a vocabulary for describing
  properties and classes of RDF resources, with a
  semantics for generalization-hierarchies of such
  properties and classes.
• OWL adds more vocabulary for describing
  properties and classes among others, relations
  between classes (e.g. disjointness), cardinality
  (e.g. "exactly one"), equality, richer typing of
  properties, characteristics of properties (e.g.
  symmetry), and enumerated classes.

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Ontology Related Language
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RDQL Tutorial
http//phpxmlclasses.sourceforge.net/rdql.html
SELECT vars FROM documents WHERE Expressions AND
Filters USING Namespace declarations
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Syntax Where, And

• Where indicate constraints that RDF triples
  (subject, predicate, object)
• And indicates constraints that RDQL variables
  must follow

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Examples

• Example If A is friend of B and B is friend of A
  report them
• Query
• SELECT ?x,?y
• FROM ltpeople.rdfgt
• WHERE (?x,ltdtfriendgt,?y), (?y,ltdtfriendgt,?x)
• AND ?xltgt?y
• USING dt for lthttp//foo.orggt, rdf for
  lthttp//www.w3.org/1999/02/22-rdf-syntax-nsgt
• Result
• Array (
• 0 gt Array ( ?x gt http//foo.org/persons/Car
  l ?y gt http//foo.org/persons/Peter )
• 1 gt Array ( ?x gt http//foo.org/persons/Pet
  er ?y gt http//foo.org/persons/Carl )
• )

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http//phpxmlclasses.sourceforge.net/rdql.html

• Indicate name and age of all the individuals
  older than 20
• SELECT ?y
• FROM ltpeople.rdfgt
• WHERE (?x,ltdtagegt,?z),(?x,ltdtnamegt,?y)
• AND ?zgt20
• USING dt for lthttp//foo.orggt, rdf for
  lthttp//www.w3.org/1999/02/22-rdf-syntax-nsgt

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Online Example RQL

• Basic Schema Navigation Queries
• subClassOf(Artist)
• subPropertyOf(creates)
• leafclass(Artist)
• leafproperty(creates)
• topclassleafclasstoppropertyleafproperty
• domain(creates)range(creates)
• Namespace(Artist)

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RQL - cont

• Class Property Querying
• Which classes can appear as domain and range of
  the property creates?
• SELECT C1, C2
• FROM C1createsC2
• SELECT X, Y
• FROM ClassX, ClassY, XcreatesY
• What if?
• SELECT X, Y
• FROM XcreatesY

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RQL - cont

• Querying Resource Descriptions
• SELECT X
• FROM ArtistX
• SELECT X, Y
• FROM XcreatesY

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RQL - cont

• SELECT Y
• FROM XtitleY
• WHERE X like "www.artchive.com

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OWL-QL Overview

• The model
• OWL-QL follows a simple request-response model.
  The querying agent, or client, issues a query to
  the answering agent, or server. As with P2P
  networks, the notions of client and server become
  blurry, because agent 1 may ask agent 2 for an
  answer, who may then turn around and ask agent 3
  for an answer to relay to agent 1.

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OWL-QL Example 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) must-bind ?x
• A White

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1. Soap Tags

• ltSOAP-ENVEnvelope xmlnsSOAP-ENV"http//schemas.
  xmlsoap.org/soap/envelope/" SOAP-ENVencodingStyle
  "http//schemas.xmlsoap.org/soap/encoding/"gt
• ltSOAP-ENVBodygt

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2. Query Tag

• ltowl-qlquery xmlnsowl-ql"http//www.w3.org/2003
  /10/owl-ql-syntax" xmlnsvar"http//www.w3.org/2
  003/10/owl-ql-variables" xmlnsrdf"http//www.w3
  .org/1999/02/22-rdf-syntax-ns"
  xmlnsrdfs"http//www.w3.org/2000/01/rdf-schema"
  xmlnsowl"http//www.w3.org/2002/07/owl"gt

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3. Premise

• ltowl-qlpremisegt
• ltrdfRDFgt
• ltrdfDescription rdfabout"C1"gt
• ltrdftype rdfresource"Seafood-Course"/gt
• ltdrink rdfresource"W1"/gt
• lt/rdfDescriptiongt
• lt/rdfRDFgt
• lt/owl-qlpremisegt

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4. Query

• ltowl-qlqueryPatterngt
• ltrdfRDFgt
• ltrdfDescription rdfabout"W1"gt
• lthas-color rdfresource"http//www.w3.org/2003/10
  /owl-ql-variablesx"/gt
• lt/rdfDescriptiongt
• lt/rdfRDFgt
• lt/owl-qlqueryPatterngt
• ltowl-qlmustBindVarsgt ltvarx/gt
• lt/owl-qlmustBindVarsgt

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KB Pattern

• ltowl-qlanswerKBPatterngt
• ltowl-qlkbRef rdfresource"http//ontolingua.stan
  ford.edu/wines.owl"/gt
• lt/owl-qlanswerKBPatterngt
• ltowl-qlanswerSizeBoundgt5lt/owl-qlanswerSizeBoundgt
  
• lt/owl-qlquerygt

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OWL Layering

• OWL has a layered architecture with successive
  layers providing more expressivity.
• OWL Full corresponds to RDF.
• OWL DL is OWL restricted to a DL/FOL fragment,
  allowing the use of DL reasoning techniques.
• OWL Lite has further restrictions intended to
  ease implementation and provide easy entry for
  those familiar with frame-like languages.
• Layered syntax and semantics
• DL semantics are normative

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OWL Layering

• OWL Lite
• Quantification Simple number restrictions (0/1)
• Subclass and Equivalence axioms relating class
  names
• OWL DL
• Boolean expressions Arbitrary number
  restrictions
• Axioms relating arbitrary descriptions
• Disjointness
• OWL Full
• No restrictions on separation of interpretations
  (class-as-instance, class-as-property etc.)
• Redefinition of built-in vocabulary allowed