after midterm Flashcards
FOL
First Order Logic
In terms of FOL, what is the following:
Objects:
Relations:
Functions:
- Objects: people, houses, numbers, theories, Ronald McDonald, colors,
baseball games, wars, centuries . . . - Relations: red, round, bogus, prime, multistoried . . .,
brother of, bigger than, inside, part of, has color, occurred after, owns,
comes between, . . . - Functions: father of, best friend, third inning of, one more than, end of
In terms of FOL, what is the basic elements
Provide an example of a family tree using FOL
Ontological Engineering
General and flexible representations for complex
domains.
Upper ontology:
The general framework of concepts
Categories and Objects
Stuff: a significant portion of reality that seems to defy any obvious
individuation—division into distinct objects
Intrinsic: they belong to the very substance of the object, rather than to the
object as a whole.
Extrinsic: weight, length, shape
Substance: a category of objects that includes in its definition only intrinsic
properties (mass noun).
Count noun: class that includes any extrinsic properties
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Events
Mental Objects
Mental objects are knowledge in someone’s head (or KB)
Propositional attitudes that an agent can have toward mental objects
* Eg: Believes, Knows, Wants, and Informs
Lois knows that Superman can fly:
Knows(Lois, CanFly(Superman))
Modal Logic
Sentences can sometimes be verbose and clumsy. Regular logic is concerned with
a single modality, the modality of truth.
Modal logic addresses this, with special modal operators that take sentences
(rather than terms) as arguments
Semantic networks
- convenient to perform inheritance reasoning
- Eg: Mary inherits the property of having two legs. Thus, to find out how many
legs Mary has, the inheritance algorithm follows the MemberOf link from Mary
to the category she belongs to and then follows SubsetOf links up the hierarchy
until it finds a category for which there is a boxed Legs link
Description logics
- notations that are designed to make it easier to describe definitions and
properties of categories - evolved from semantic networks in response to pressure to formalize what the
networks mean while retaining the emphasis on taxonomic structure as an
organizing principle - Principal inference tasks:
- Subsumption: checking if one category is a subset of another by
comparing their definitions - Classification: checking whether an object belongs to a category
- The CLASSIC language (Borgida et al., 1989) is a typical description logic
- Eg: bachelors are unmarried adult males
- Bachelor = And(Unmarried, Adult, Male)
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Belief revision:
inferred facts will turn out to be wrong and will have to be
retracted in
Truth maintenance systems
or TMSs, are designed to handle complications of
any additional sentences that inferred from a wrong sentence.
Justification-based truth maintenance system (JTMS)
- Each sentence in the knowledge base is annotated with a justification
consisting of the set of sentences from which it was inferred - Justifications make retraction efficient
- Assumes that sentences that are considered once will probably be
considered again
