Ontological Engineering Knowledge presentation

Ontological Engineering Knowledge Representation. Complex domains – e.g. internet shopping agents – require very general & flexible representations • should include actions, time, physical objects, beliefs, …. – ontological engineering • is the process of finding/deciding on representations for these abstract concepts – somewhat like Knowledge Engineering • but at a larger scale • generalized to a more complex real world 4 Ontological Engineering • We use a general framework of concepts – an upper ontology • "upper" due to the diagrammatic convention of putting the most general at the top 5 Ontological Engineering • a sample upper ontology 6 Ontological Engineering – there are limitations to a FOL representation – e.g. there are exceptions to generalizations • they hold only to some degree • "tomatoes are red" • but there are green, yellow, even purple tomatoes – exceptions & uncertainty are important topics • however, they are orthogonal to a general ontology – & their discussions are deferred 7 Ontological Engineering • is there one general purpose ontology? – the philosophical answer is: Possibly • our goal – develop a general purpose ontology – one that's usable in any special purpose domain • with the addition of domain-specific axioms – in any sufficiently demanding domains • different areas of knowledge must be unified • involves several areas simultaneously 8 Ontological Engineering • we begin with objects & categories – organizing objects into categories • though physical interaction involves individual objects • reasoning processes need to operate at the level of categories 9 Objects & Categories • Take a example – a shopper might have the goal of buying a basketball, rather than a particular basketball such as BB. • FOL representation of categories (Alternative approaches) – 1. use predicates • Basketball (b) • then the category as the set of its members – 2. or, treat the category as an object • reify the category: Basketballs • allows Member(b, Basketballs) or b  Basketballs • allows Subset(Basketballs, Balls) or BasketBalls  Balls • so, treat categories as more complex objects • with Member, Subset relations defined for them 10 Category Organization • The category mechanism – organizes & simplifies a KB through inheritance • all instances of food are edible • fruit is a subclass of food • apples is a subclass of fruit • then an apple is edible – subclass relations organize categories • into a taxonomy or taxonomic hierarchy