Ontologies Flashcards
what are 2 disadvantages of propositional logic?
- quite hard to construct and quite hard to read
2. becomes very big even for small problems
3 elements used in ontology
- classes - name and set of properties that describe a certain set of individuals in the domain
- instances - members of the set defined by classes
- properties - assert facts about the instances
whats a transitive property?
if it holds for p1 & p2 and p2 & p3 it also holds for p1 & p3
> e.g. colleagues, team members
whats a symmetric property?
symmetric property: if it holds for p1,p2 it also holds for p2,p1
> e.g. friend
whats a functional property?
functional property: if it holds for p1,p2 it cannot hold for p1,p3
> e.g. mother
when are two classes equivalent?
two classes are equivalent when they contain the same individuals and have the same definition
when are two classes complementary?
two classes are complementary if one class contains all the individuals that are not in the other class
when are two classes disjoint?
two classes are disjoint when they do not contain the same individuals
union and intersection - mapped to logic?
union - a OR b
intersection - a AND b
whats an asymmetric property?
an asymmetric property NEVER holds in both directions
> is p(x,y) holds then p(y,x) never holds
whats an inverse functional property?
the value for the property uniquely identifies the instance
> if p(x,y) and p(z,y) then x = z
whats a reflexive property?
reflexive property: every individual is always related to itself by property
> for every x p(x,x) holds
whats an irreflexive property?
irreflexive property: no individual is ever related to itself by that property
>for every x p(x,x) does not hold
whats an inverse property?
inverse property: one property is always the inverse of the other property
>if inverse(p,q) and p(x,y) then q(y,x) always holds
