DAML+OIL Ontology Tutorial

1. DAML+OIL Ontology Tutorial Chris Wroe, Robert Stevens (Sean Bechhofer, Carole Goble, Alan Rector, Ian Horrocks….) University of Manchester

2. 3 goals for today • Why use DAML+OIL ontologies? • What are the design principles? • What is the syntax of DAML+OIL?

3. Applications Pizza DB Providing a controlled vocabulary 1 • Prevent the user spelling magherita differently • Prevent me from adding a type of car to that field • c) Ensure the users and application have the same notion of a magherita pizza • d) Help an application answer queries such as how many vegetarian pizza’s were sold?

4. Applications Schema integration Ontology Schema 2 Schema 1 Database 1 Database 2 Schema 3 Database 3

5. Applications TAMBIS

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8. 1. List Margherita Capricciosa …. …. …. …. …. How are ontologies encoded? 2. Tree 3. Multiple hierarchy spicy pizza meat pizza American hot pizza

9. Principles Property driven classification • Most taxonomies are hand crafted • Difficult to maintain when large or intricate • Become too large to use but too small to capture what you want to say • Now possible to calculate a hierarchy • Supply the ‘lego’ building blocks to allow the ontology author or user to define classes • Use reasoning to check consistency and calculate classification based on these definitions

10. Descriptions are key • Classification driven by description • Effort moved from manual placement of classes in a taxonomy to formal definition of classes. • The same classes can be classified in different ways for different purposes

11. Applications can dynamically build descriptions • Pizza finder

12. Exercise 1 • Specific Tasks • Use the information in the menus to write definitions for margherita, la reine, soho and neptune pizzas • List the concepts and relationships used in the definitions • General questions • How else could do you describe types of pizza? • What parts of the description will drive classification? • What kinds of concepts are used in the description?

13. Pizza template • Pizza types are mainly defined in terms of their topping ingredients • Many high level groups of pizza types depends on a categorisation of ingredients

14. Exercise 2 • Use card sorting to categorise pizza ingredients.

15. Exercise 2 beginning with OilEd • Open an ontology (pizza-tutorial-ex-2.daml) • Set the namespace • Add classes to an ontology • (ham, olive, parmesan) • Add superclasses (parents) to a class • (meat, fish, vegetable, and cheese ingredient) • Reason with the ontology (nothing happens) • Save an ontology

16. Principles Organisation Terms • Classification • A grouping of things into classes • Instances • Members of a class • Hierarchy • A stratified organisation of things in which there is a top and a bottom • Taxonomy • A hierarchical classification

17. Disjointness • In the DAML+OIL world every class is assumed to overlap with every other. • We need to explicitly state something cannot be a member of two classes at the same time e.g. man and women

18. Exercise 3 – adding a disjoint axiom • Make tuna a subclass of both meat and fish ingredient classes. • Verify the ontology • Add a disjoint axiom between meat and fish ingredient. • Send the ontology to the reasoner (verify). • At this point also add disjoint axioms between meat, cheese and vegetableingredient classes.

19. Relationships • Non taxonomic links • Relationship type is called a Property • Properties can be placed in a taxonomy of their own

20. Exercise 4 • Add a property has_topping_ingredient • Add a property has_part • Make has_part a super property of has_topping_ingredient

21. Restrictions • Describing a class in terms of its relationships to other classes • Restricting class membership to only those individuals that posses these criteria.

22. Exercise 5 • Create a restriction relating margherita pizza to its topping ingredients mozzarella and tomato

23. Necessary and sufficient criteria • To be a member I must have these relationships (necessary = subclassOf) • If I have these relationships I must be a member (necessary and sufficient = sameClassAs)

24. Exercise 6 • Load ontology pizza-tutorial-ex-6.daml • Create a class called ‘cheesy pizza’ as a subclass of pizza which has a topping ingredient of cheese ingredient. • Change to a SameClassAs definition • Send the ontology to the reasoner (verify).

25. Negation and disjunction • DAML+OIL allows logical expressions to be used anywhere a named class could be used. • Allows much more precision and flexibility in defining classes.

26. Exercise 7 • Write down a definition for a vegetarian pizza • Create a new class in the ontology called vegetarian pizza and represent the paper based definition in DAML+OIL • Send the ontology to the reasoner.

27. Types of relationship • hasClass – members ofclass A have this relationship with some members of class B • toClass – members of class A (if they have this relationship) only have this relationship with members of class B

28. Exercise 8 • Change restriction type in the vegetarian pizza to toClass. • Send the ontology to the reasoner

29. Open world assumption • Open world of the web - always assumes someone could add some extra information • Some one could come along and add a statement to say margherita pizza has ham on it. • We have to ‘cap off’ the description to say margherita pizza has these toppings and I know it doesn’t have any meat ingredients. (It may have herbs etc.)

30. Exercise 9 • ‘Cap off’ the definition of margherita pizza with a toClass restriction. • Send the ontology to the reasoner. • (Note we can now explicitly say Neptune has no cheese ingredient in the same way) • Load ontology pizza-tutorial-ex-10.daml to see more definitions.

31. Transitivity • Vegetarians are picky! • Soho pizza isn’t classed as vegetarian in the menu • Some cheeses are made with meat products (rennin) • The ingredient property is transitive. If parmesan has a meat ingredient in it any pizza with parmesan should be also be classed as containing a meat ingredient

32. Exercise 10 • Make the has_part relationship transitive • Add rennin as a subclass of meat ingredient • Add a restriction on parmesan to say it has_part some rennin. • Send the ontology to the reasoner.

33. Cardinality • More precise numerical constraints can be placed on relationships. • It should be read as ‘members of class A are related by this property to this many members of class B ‘

34. Exercise 11 • Change the definition of cheesy pizza to ‘a pizza with at least 2 types of cheese’ • Add a new type of pizza called ‘four cheese pizza’ which has exactly four topping ingredients of type cheese ingredient • Use the reasoner • Add a disjoint axiom between parmesan and mozzarella. • Use the reasoner

35. Domain and range constraints • Used to specify what classes can be used with properties • May be useful but can have undesirable effects

36. Exercise 12 • For has_topping_ingredient add a domain of pizza and a range of ingredient • Make intentional errors to test the system e.g. add ham as a topping ingredient of onion and add four cheeses pizza as a topping of margherita pizza. • Use the reasoner • Examine the superclasses of onion • Add a disjoint axiom between pizza and ingredient • Use the reasoner

37. Things not covered • Inverse properties, symmetrical properties, unique properties. • Subclass and sameClass axioms. • Use of individuals

38. Current example ontologies • GONG • myGrid

39. Current example applications • Clinergy – not DAML+OIL • PEDro