Exam P7/8 Flashcards
What were the primary motivations behind the development of Description Logics (DLs)? Specifically, what issues related to the semantics of Frame systems and the limitations of First-Order Logic (FOL) are mentioned as key drivers?
- The fact that FOL had semi-decidability
- Combining the natural representation and reasoning primitives of Frame systems with the semantics of FOL
What are some of the basic ideas behind Description Logics?
- Small is beautiful, development by layers, formalism is developed and named
- Decidability
- Formal semantics, in general DLs are Monotonic, but there are some that allow defaults
- Natural representation, from a human perspective
What are the “development by layers”?
Refers to the approach of building DL formalisms by incrementally adding expressive primitives, resulting in a family of DLS with varying capabilities
What is KL-ONE, and what were its main architectural components? Describe the purpose of the Terminological component (T-BOX) and the Assertional component (A-BOX)
KL-ONE is a very efficient KRR system, developed by layers, with the small is beautiful philosophy, composed by 2 components:
- Terminological component, T-BOX, definitions of concepts, where terminology is defined
- Assertional component, A-BOX, describes a particular world, the assertions and instances of a particular world
What is the role of taxonomic relations in defining concepts within KL-ONE?
The taxonomic relations are used to define a hierarchy of concepts
What are the main reasoning capabilities supported by KL-ONE? Briefly explain inheritance, subsumption, and classification
KL-ONE supports inheritance, subsumption (see if one concept is more general than another), and classification (find if the place in the hierarchy where the concept should be introduced).
Describe the semantics of DLs like KL-ONE? What are the key notions of extension and the universe of discourse? What does a concept represent within this semantic framework?
Based on the notions of E (extension) and D (universe of discourse):
- Each concept represents a subset of D
- Each role represents a set of pairs of these entities, a subset of DxD
- Both concepts and roles correspond to relationships in FOL
- We associate to each concept and to each role the relations denoted by them, these associated sets are Extensions
What is the top-most concept in the KL-ONE concept hierarchy?
The top-most concept is THING
