Ontology Engineering

1
Ontology Engineering

• Lab 5 September 29, 2014

2
SPARQL

• SPARQL Protocol and RDF Query Language
• A query language to retrieve and manipulate data
  stored in RDF format.
• Analogous to SQLs role in the context of
  relational databases
• SPARQL 1.0 became an official W3C Recommendation
  on 15 January 2008
• SPARQL, 1.1 became an official W3C Recommendation
  on March 21, 2013

3
The Structure of a SPARQL (Select) Query

• The select clause lists the information you want
  to see.
• The where clause is a set of statements that
  pulls the information
• SELECT ?class
• WHERE
• ?class lthttp//www.w3.org/1999/02/22-rdf-syntax-
  nstypegt lthttp//www.w3.org/2002/07/owlClassgt .

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SPARQL Useful Keywords

• PREFIX keyword associates a prefix label with an
  IRI.
• Simplifies writing queries on data that uses
  classes and properties from multiple namespaces
• PREFIX rdfhttp//www.w3.org/1999/02/22-rdf-syntax
  -ns
• PREFIX owlhttp//www.w3.org/2002/07/owl
• SELECT ?class
• WHERE
• ?class rdftype owlClass .
• Instead of
• SELECT ?class
• WHERE
• ?class lthttp//www.w3.org/1999/02/22-rdf-syntax-
  nstypegt lthttp//www.w3.org/2002/07/owlClassgt .
  

5
Keystroke Shortcuts

• Using to repeat the subject term over a set
  of statements in a where clause
• SELECT ?domain ?property ?range
• WHERE
• ?property rdftype owlObjectProperty
• rdfsdomain ?domain
• rdfsrange ?range .

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SPARQL Useful Keywords

• DISTINCT keyword removes duplicate values from
  the result set
• LIMIT keyword restricts the result set to some
  user defined number of values
• PREFIX rdfslthttp//www.w3.org/2000/01/rdf-schema
  gt
• SELECT DISTINCT ?class ?superclass
• WHERE
• ?class rdfssubClassOf ?superclass .
• LIMIT 25
• Returns no more that 25 unique pairs of classes
  and their superclasses

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SPARQL Useful Keywords

• OPTIONAL keyword allows information to be added
  to the solution where the information is
  available, but does not reject the solution
  because some part of the query pattern does not
  match
• PREFIX rdfslthttp//www.w3.org/2000/01/rdf-schema
  gt
• SELECT ?class ?superclass ?label
• WHERE
• ?class rdfssubClassOf ?superclass .
• OPTIONAL ?class rdfslabel ?label .
• Returns both classes that have and do not have
  labels

8
Exploring DBPedia

• DBPedia is a structured store of information from
  Wikipedia. (see http//en.wikipedia.org/wiki/DBped
  ia for a summary)
• SPARQL endpoint can be found at
  http//dbpedia.org/sparql
• Pages for individual resources can be found at
  http//dbpedia.org/page/......

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Different Uses of the Keyword OPTIONAL

• The following query returns routes that are
  related to both terminal points
• SELECT ?route ?terminalpointA ?terminalpointB
• WHERE
• ?route rdftype dbpedia-owlRouteOfTransportation
  .
• ?route dbppropterminusA ?terminalpointA .
• ?route dbppropterminusB ?terminalpointB .
• LIMIT 100

10
Different Uses of the Keyword OPTIONAL

• This query returns routes and their terminal
  points if they have them both
• SELECT ?route ?terminalpointA ?terminalpointB
• WHERE
• ?route rdftype dbpedia-owlRouteOfTransportation
  .
• OPTIONAL ?route dbppropterminusA
  ?terminalpointA .
• ?route dbppropterminusB
  ?terminalpointB .
• LIMIT 100

11
Different Uses of the Keyword OPTIONAL

• This query returns routes and their terminal
  points if they have either of them
• SELECT ?route ?terminalpointA ?terminalpointB
• WHERE
• ?route rdftype dbpedia-owlRouteOfTransportation
  .
• OPTIONAL ?route dbppropterminusA
  ?terminalpointA .
• OPTIONAL ?route dbppropterminusB
  ?terminalpointB .
• LIMIT 100

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Different Uses of the Keyword OPTIONAL

• This query returns routes and their terminal
  point A if they have one else it will return
  their terminal point B if they have one
• SELECT ?route ?terminalpoint
• WHERE
• ?route rdftype dbpedia-owlRouteOfTransportation
  .
• OPTIONAL ?route dbppropterminusA ?terminalpoint
  .
• OPTIONAL ?route dbppropterminusB ?terminalpoint
  .
• LIMIT 100

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Exercises

• Write queries on Dbpedia that return the
  following results
• Select routes and their length in miles
  (dbpproplengthMi)
• Select routes and their lengths
  (dbpedia-owllength)
• Select routes and both their length in miles and
  length if they have them both. (LIMIT BY 500)
• Select routes and their length in miles or their
  length if they have either of them. (LIMIT BY
  500)
• Select routes and their length in miles if they
  have one or otherwise their length. (LIMIT BY
  500)
• Select routes that have terminal points that are
  instances of classes rather than literals
  (strings, numbers, etc.)