Fictional Universes and OWL! – Part III

In the second year of my teaching this class, I started experimenting to see if other fictional universes could also be modeled to OWL (Web Ontology Language) ontologies and questions can be formulated regarding inconsistency detection, use of the correct role restriction, entailment etc. Also, I wanted to see if SWRL rules can be formulated similar to the Pokemon GOntology example, and hence be simulated as a rule-based game! These are my experiments with the Lord of the Rings fictional universe!

lotr

You have a Lord of the Rings Ontology with the following axioms:

Classes: Ring_Of_Power, LOTR_Region, Man, Nazgûl

Object Properties: lives_in, possess

Individual: Mordor (instance of LOTR_Region).

Question: You want to represent Nazgûl using a subclass axiom and role restrictions. Select one description from the following options. Explain your choice in 1-2 sentences.

  1. (Nazgûl) subclassOf (
    • Man
    • AND possess Minimum 1 Ring_Of_Power
    • AND lives_in AllValuesFrom Mordor)
  2. (Nazgûl) subclassOf (
    • Man
    • AND possess SomeValuesFrom Ring_Of_Power
    • AND lives_in SomeValuesFrom Mordor)
  3. (Nazgûl) subclassOf (
    •  Man
    • AND possess SomeValuesFrom Ring_Of_Power
    • AND lives_in HasValue Mordor)

Answer: Description 3 is correct, since Nazgul can possess other objects (someValuesFrom allows it), but primarily, because Mordor is an individual, you can only use HasValue restriction over the “live_in” property.

And once again, you can demonstrate inconsistency errors using this fictional Lord of the Rings Ontology.

Suppose, you have a Lord of the Rings Ontology with the following entities and axioms:

Classes: Elven_Sword, Palantir, Humanoid, Hobbit

Object Properties: possess

Individual:

  • Pippin (instance of Hobbit),
  • Palantir_One (instance of Palantir)

disjointWith (Elven_Sword, Palantir)

(Hobbit) subclassOf (

  • Humanoid AND
  • possess ONLY ElvenSword)

Pippin possess Palantir_One

Question: Is your Lord of the Rings Ontology consistent or inconsistent? Justify your answer.

Answer: Inconsistent. Since Hobbit are subclassOf class of individuals that can possess only ElvenSword and ElvenSword and Palantir are disjoint. So Hobbits can not possess Palantirs, but Pippin possesses Palantir_One which creates the inconsistency.

And finally, you can formulate SWRL rules using the Lord of the Rings Ontology axioms. The validity of these rules can also be discussed. 

Question: Which of the following rules are not possible using SWRL? Justify your answer.

  1. Elf(?x), Dwarf(?y), has_killed(?x, ?x_orcs), has_killed(?y, ?y_orcs), greaterThan(?x_orcs, ?y_orcs) -> is_better(?x, ?y)
  2. Man(?x), not influencedBy(?x, ?y), Palantir(?y) -> GoodMan(?x)
  3. Elf(?x), has_killed(?x, ?x_orcs), add(?x_orcs_new, ?x_orcs, 1) -> has_killed(?x, ?x_orcs_new)
  4. Man(?x), (possess exactly 1 Ring_Of_Power)(?x), lives_in(?x, Mordor) -> Nazgûl(?x)

Answer: SWRL rule (2) is not allowed because negation and SWRL rule (3) is not allowed because recursion!