|Categories: categories are basic concepts for classifying the objects of a knowledge domain into different groups or hierarchies. In philosophy, the category systems of different authors can differ considerably. Concepts which are not suitable for classifying are transcendentals, e.g. the concept of similarity. However, these concepts are again applicable to categorized objects._____________Annotation: The above characterizations of concepts are neither definitions nor exhausting presentations of problems related to them. Instead, they are intended to give a short introduction to the contributions below. – Lexicon of Arguments. |
|Norvig I 440
Categories/Ai research/Norvig /Russell: The organization of objects into categories is a vital part of knowledge representation. Although interaction with the world takes place at the level of individual objects, much reasoning takes place at the level of categories. Categories also serve to make predictions about objects once they are classified. One infers the presence of certain objects from perceptual input, infers category membership from the perceived properties of the objects, and then uses category information to make predictions about the objects. >Knowledge representation/AI research, >Ontology/AI research.
There are two choices for representing categories in first-order logic: predicates and objects.
Inheritance: Categories serve to organize and simplify the knowledge base through inheritance. If we say that all instances of the category Food are edible, and if we assert that Fruit is a subclass of Food and Apples is a subclass of Fruit, then we can infer that every apple is edible. We say that the individual apples inherit the property of edibility, in this case from their membership in the Food category.
Norvig I 454
Reasoning systems for categories: a) semantic networks: use labels like male/female, “mother/father etc. The semantic network notation makes it convenient to perform inheritance reasoning (…).
Norvig I 455
Inheritance: becomes complicated when an object can belong to more than one category
or when a category can be a subset of more than one other category; this is called multiple inheritance. In such cases, the inheritance algorithm might find two or more conflicting values answering the query. For this reason, multiple inheritance is banned in some object-oriented programming (OOP) languages, such as Java, that use inheritance in a class hierarchy. It is usually allowed in semantic networks (…)
Norvig I 456
Description logic: Description logics are notations that are designed to make it easier to describe definitions and properties of categories. The principal inference tasks for description logics are subsumption (checking if one category is a subset of another by comparing their definitions) and classification (checking whether an object belongs to a category).
Norvig I 456
VsDescription logics/Norvig: either hard problems cannot be stated at all, or they require exponentially large descriptions! ((s) For a solution see >Conceptual space/Gärdenfors; >Semantic Web/Gärdenfors. (GärdenforsVsRussell, Stuart/GärdenforsVsNorvig). >Description logic/AI research._____________Explanation of symbols: Roman numerals indicate the source, arabic numerals indicate the page number. The corresponding books are indicated on the right hand side. ((s)…): Comment by the sender of the contribution. The note [Author1]Vs[Author2] or [Author]Vs[term] is an addition from the Dictionary of Arguments. If a German edition is specified, the page numbers refer to this edition.
Stuart J. Russell
Artificial Intelligence: A Modern Approach Upper Saddle River, NJ 2010