Ontology Engineering

1. Ontology Engineering Lab #2 – September 9, 2013

2. Review – Ontology Identifiers and Versioning Ontology IRI accessible by Current Version Ontology 1.0 Ontology 1.1 Ontology 1.2 Ontology 1.n Version 1.0 IRI Version 1.1 IRI Version 1.2 IRI Version 1.n IRI

3. Review – Violations of Versioning Uniqueness Constraints Ontology 1 Ontology IRI: XXXXX Ontology 2 Ontology 1 Ontology IRI: XXXXX Ontology 2 Version IRI: YYYYY

4. Data Definition Languages • Computer processable data requires structures that are defined in a manner to which applications can respond as expected • Structured Query Language – contains statements that build database tables CREATE TABLE customers ( customer_id number(10) not null, customer_name varchar2(50) not null, address varchar2(50), city varchar2(50), state varchar2(25), zip_code varchar2(10), CONSTRAINT customers_pk PRIMARY KEY (customer_id) ); * * from http://www.techonthenet.com/sql/tables/create_table.php

5. RDF, RDF-S and OWL • The Resource Description Framework (RDF), Resource Description Framework Schema (RDF-S) and Web Ontology Language (OWL) are a trio of languages that allow us to describe the structure of ontologies • The content of these languages is on the web at these URLs: • RDF: http://www.w3.org/1999/02/22-rdf-syntax-ns# • RDF-S: http://www.w3.org/2000/01/rdf-schema# • OWL: http://www.w3.org/2002/07/owl#

6. Well Formed Expressions • RDF specifies a regular syntax for well formed expressions • rdf:statement – a simple expression that relates one entity to another • rdf:subject – the entity the statement is about • rdf:predicate – the relationship said to hold between the two entities • rdf:object – the entity that is related to the subject • Humansaremortal • UB’s website homepage has URLhttp://www.buffalo.edu/ • Remusis the brother of Romulus

7. RDF Graphs Nodes Remus Romulus is_brother_of founder_of Rome Edges The direction of the edges is always away from the subject and towards the object of the statement

8. A Couple of Rules for RDF Statements • Subject and Predicate have to be resources • Object – can be either a resource or a literal • Behind the display in Protégé the statement: Humansaremortal will look like: <http://www.buffalo.edu/IE500/rjr9/OEF13_000013><http://www.buffalo.edu/IE500/rjr9/OEF13_000108> <http://www.buffalo.edu/IE500/rjr9/OEF13_000072> • Andthe statement: The URL of UB’s websiteis http://www.buffalo.edu/ will look like: <http://www.buffalo.edu/PHI598/rjr9/OEF13_001158> <http://www.buffalo.edu/PHI598/rjr9/OEF13_000002> "http://www.buffalo.edu/"

9. RDF, RDF-S and OWL • owl:Class is used to declare an entity to be a class • rdfs:subClassOf is used to declare that one class is a subclass of another • rdf:type is used to declare that a resource is an instance of a given type • rdf:Property is used to declare that a resource is a relation… • Between a resource and an annotation (annotation property) • Between a resource and a literal value (datatype property) • Between a resource and another resource (object property) • rdfs:subPropertyOf is used to declare that one property is a subproperty of another

10. 1st (poor) Attempt at “Ontologizing” the Customer Table Zip Code State has ZIP code has State has ID Customer ID Customer City has City has name has address Customer Name Address

11. Improved Attempt at Ontologizing Act Of Inhabitance Customer Person Name agent in has role participates in designates Customer ID Person designates Facility located in Land Lot part of Geospatial Region near City designates designates part of Address Zip Code State

12. Enriching a Taxonomy with Restrictions • owl:Restriction used to create an anonymous class (as opposed to a named class) that can be used to describe either necessary or necessary and sufficient conditions for class membership • Existential Restrictions: members have at least one member of the object of the restriction • Example: persons are children of at least one person • Example: orchestras have at least one section of woodwinds • Universal Restrictions: members have only members of the object of the restriction • Example: temporal intervals are composed of only temporal intervals • Example: organizations have subsidiary only organization

13. Enriching a Taxonomy with Restrictions • Necessary Restrictions are a means to define subclass relationships • Example: humans are mortal • Example: universities are institutions of higher-education • Example: bicycles are two-wheeled vehicles • Necessary and Sufficient Restrictions are a means to create equivalent class relationships • Example: days are 24 hour periods • Example: bachelors are unmarried males • Example: even numbers are divisible by 2

14. Building a Taxonomy – Common Problems • In schema.org, the expected type of AddressCountry is a country, whereas the other components of a postal address have expected types of Text (http://schema.org/PostalAddress) Use – Mention Errors Part of rather than subclass of

15. Building a Taxonomy – Common Problems • In Thomasnet.com(http://www.thomasnet.com/browse) classes are formed by conjunctions and the class hierarchy contains examples of subclasses based on search patterns Narrower in meaning than rather than subclass of Logic of Terms

16. Building a Taxonomy – Common Problems • In the Phenotypic Quality Ontology (http://purl.obolibrary.org/obo/PATO_0000320) classes are subclasses by hue. Narrower in meaning than rather than subclass of

17. Building a Taxonomy – Common Problems Non-Disjoint Classes

18. Building a Taxonomy – Common Problems Different Identity Criteria

19. Reading • Guus Schreiber’s discussion of OWL restrictions at: http://www.cs.vu.nl/~guus/public/owl-restrictions/