week 4

Question 1

OWL

Answer 1

Web Ontology Language, a well understood and expressive language,

• no unique naming assumption,
• open world assumption,
• classes are interpreted as sets,
• axioms restrict the potential members of a class

Question 2

open world assumption (OWA)

Answer 2

nothing is assumed to be true or false unless it is explicit knowledge or derived from axioms or known facts

Question 3

closed world assumption (CWA)

Answer 3

if something is not explicitely stated to be true, it is assumed to be false

Question 4

OWL has two kinds of sublevel classes

Answer 4

1. owl:Thing. anything is a thing in OWL
2. owl:Nothing. is a class that consists of nothing

Question 5

Equivalent classes

Answer 5

contain the same individuals and have the same definition

Question 6

complement

Answer 6

contains all individiuals that are not in the class

Question 7

disjoint classes

Answer 7

do not contain all individuals. the 2 classes can never overlap

Question 8

union

Answer 8

contains all indiciduals that belong to the classes of the union

Question 9

disjoint union

Answer 9

a union of mutually disjoint classes

Question 10

intersection

Answer 10

contains individuals that belong to both classes

Question 11

enumerate

Answer 11

add up all members of a class

Question 12

object properties

Answer 12

connects two objects to each other

Question 13

data type properties

Answer 13

connects a value to an object

Question 14

annotation properties

Answer 14

of type owl:AnnotationProperty cannot be used in restrictions

Question 15

symmetric property

Answer 15

used to specify that a property always holds in both directions

Question 16

asymmetric property

Answer 16

used to specify that property never holds in both directions

Question 17

transitive property

Answer 17

used to specify that a property propagates over itself

Question 18

functional property

Answer 18

used to specify that a property has only one value for any particular instance

Question 19

inverse functional property

Answer 19

used to specify that a value for the property uniquely identifies an instance

Question 20

reflexive property

Answer 20

used to specify that every individual is always related to itself by that property

Question 21

irreflexive property

Answer 21

used to specify that no individual is ever related to itself via that property

Question 22

inverse property

Answer 22

used to specify that one property is always the inverse of another property

Question 23

equivalent property

Answer 23

used to specify that two properties always co-occur

Question 24

disjoint property

Answer 24

used to specify that two properties never co-occur

Question 25

property chain

Answer 25

used to specify that a property propagates over a chain of other properties

Question 26

necessary class restrictions

Answer 26

restrictions about instances in that class, uses rdfs:subClassOf

Question 27

necessary and sufficient class restrictions

Answer 27

are stronger than just necessary restrictions. uses owl:equivalentClass

Question 28

punning

Answer 28

OWL interprets two things as different things if they are used both as concepts and instances even though they have the same name