1. Joshua Scotton jscotton@dcs.warwick.ac.uk OWL-QL

2. 2 OWL Query Language) Based on DQL (DAML Query Lang.) Simple Request-Response Model http://www-ksl.stanford.edu/projects/owl-ql/

3. 3 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

4. 4 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

5. 5 A Simple OWL-QL Query The following is the actual query: 5 This would normally be included inside a SOAP message

6. 6 Response to Simple Query

7. 7 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)

8. 8 OWL-QL bindings Three types of OWL-QL bindings 1.must-bind variables lists Answers must provide bindings for all the must- bind variables 2.may-bind variables lists Answers may provide bindings for any of the may-bind variables 3.don’t-bind variables lists Answers are not to provide bindings for any of the don’t-bind variables

9. 9 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)

10. 10 Another Query Who owns a red car? Query Pattern: (owns ?p ?c) (type ?c Car) (has-color ?c Red) Must-Bind Variable: ?p Don’t-Bind Variable: ?c Answer Pattern: owns ?p a red car

11. 11 Answer patterns specify the format in which answer bindings are returned Answer Pattern: owns ?p a red car

12. 12 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 ?x Must-Bind Variables: ?x

13. 131 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

14. 14 Answer bundle size bounds specify the maximum number of answers in each “bundle” answers are delivered by the server in bundles 5 contain at most the number of query answers given by the answer bundle size bound

15. 15 The Car Query 5

16. 16 An OWL-QL answer Contains: answer pattern instances an answer bundle

17. 17 The Car Query Answer

18. 18 Online Demonstrations Try OWL-QL Query Service at http://onto.stanford.edu:8080/owql/FrontEnd

19. Questions? 19