Knowlege Representation
Ontological Engineering
Creating abstract representations using general concepts such as Events, Time, Physical Objects and Beliefs that occur in many different domains.
Upper ontology: The general framework of concepts at the top
Categories and Objects
Organizing objects into categories is a vital part of knowledge representation There are two choices for representing categories in first order logic: predicates and objects We can use predicate Basketball(b), or we can reify the category as an object, Basketballs. We could then say Member(b, Basketballs)
reify: turning a proposition into an object
We say Subset(Basketballs, Balls), abbreviated as Basketballs
Disjoint: If the categories have no members in common Ex: Males and Females Exhaustive decomposition: Ex: When Males and Females are sub classes of Animals, and an animal that is not Male is Female Partition: Disjoint exhaustive decomposition.
Physical Composition
The idea that one object can be part of another object.
- PartOf(Bucharest, Romania)
- PartOf(Europe, Earth) PartOf relation is transitive and reflexive
- PartOf(x,y)
PartOf(y,z) PartOf(x,z) - PartOf(x,x) Composite object categories can be characterized by strucural relations among parts
- Biped(a) ⇒ ∃l1, l2, b Leg(l1) ∧ Leg(l2) ∧ Body(b) ∧ PartOf (l1, a) ∧ PartOf (l2, a) ∧ PartOf (b, a) ∧ Attached(l1, b) ∧ Attached(l2, b) ∧ l1 ≠ l2 ∧ [∀ l3 Leg(l3) ∧ PartOf (l3, a) ⇒ (l3 =l1 ∨ l3 = l2)]
Upper Ontology
Drawing graphs with the general concepts at the top and more specific concepts below them