发表于: 2005.08.26 13:07
分类: 研究
出处: http://junsheng.itpub.net/post/860/39170
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Q:Why would someone want to develop an ontology?
A:Some of the reasons are:
(1) To share common understanding of the structure of information among people or
software agents
(2) To enable reuse of domain knowledge
(3) To make domain assumptions explicit
(4) To separate domain knowledge from the operational knowledge
(5) To analyze domain knowledge
Q:What is the goal of ontology?
A:Sharing common understanding of the structure of information among people or software
agents is one of the more common goals in developing ontologies (Musen 1992; Gruber 1993).
Q:What is the content of ontology?
A:The Artificial-Intelligence literature contains many definitions of an ontology; many of
these contradict one another. For the purposes of this guide an ontology is a formal explicit
description of concepts in a domain of discourse (classes (sometimes called concepts)),
properties of each concept describing various features and attributes of the concept (slots
(sometimes called roles or properties)), and restrictions on slots (facets (sometimes called
role restrictions)). An ontology together with a set of individual instances of classes
constitutes a knowledge base. In reality, there is a fine line where the ontology ends and
the knowledge base begins.
Q:what need to be done when build an ontology?
A:In practical terms, developing an ontology includes:
(1)defining classes in the ontology,
(2)arranging the classes in a taxonomic (subclass杝uperclass) hierarchy,
(3)defining slots and describing allowed values for these slots,
(4)filling in the values for slots for instances.
Q:How to estimate an ontology?
A:1) There is no one correct way to model a domain- there are always
viable alternatives. The best solution almost always depends on the
application that you have in mind and the extensions that you anticipate.
2) Ontology development is necessarily an iterative process.
3) Concepts in the ontology should be close to objects (physical or logical)
and relationships in your domain of interest. These are most likely to be
nouns (objects) or verbs (relationships) in sentences that describe your
domain.
Q:What is the principles to define the classes?
A:When defining a domain or a range for a slot, find the most general classes or class that can be respectively the domain or the range for the slots . On the other hand, do not define a domain and range that is overly general: all the classes in the domain of a slot should be described by the slot and instances of all the classes in the range of a slot should be potential fillers for the slot. Do not choose an overly general class for range (i.e.,one would not want to make the range THING) but one would want to choose a class that will cover all fillers.
The ontology should not contain all the possible information about the domain: you do not need to specialize (or generalize) more than you need for your application (at most one extra level each way).
The ontology should not contain all the possible properties of and distinctions among classes in the hierarchy.
Q: How to deal with synonyms?
A: Synonyms for the same concept do not represent different classes;
Many systems allow associating a list of synonyms, translations, or presentation names with a class. If a system does not allow these associations, synonyms could always be listed in the class documentation.
Q: How to decide the number of subclesses?
A: If a class has only one direct subclass there may be a modeling problem or
the ontology is not complete.
If there are more than a dozen subclasses for a given class then additional
intermediate categories may be necessary.
Q: What is the different of class and subclasses?
A: Subclasses of a class usually (1) have additional properties that the
superclass does not have, or (2) restrictions different from those of the
superclass, or (3) participate in different relationships than the
superclasses
