[SCL] "ontologies"

[pat hayes]

>Pat,
>
>Since you prefer the usage in semantic web circles,
>I will quote the definition from the "OWL Web
>Ontology Language Overview" of 15 Dec 2003:
>
>    OWL can be used to explicitly represent the meaning
>    of terms in vocabularies and the relationships between
>    those terms. This representation of terms and their
>    interrelationships is called an ontology.
>
>This definition has two implications for our discussion:
>
>  1. OWL "can" be used to represent the meaning
>     of terms -- in other words, there are also
>     other applications for OWL.
>
>  2. Only those applications of OWL that represent
>     the meanings of terms and their relationships
>     are called ontologies.
>
>Point #2 is the primary purpose of the KL-ONE T-box
>as opposed to the A-box.  But theories are more general,
>since they can state A-box assertions in addition to
>T-box terminologies.  Examples:  rules, constraints,
>specifications, databases, knowledge bases, etc.

OWL is also used for "A-box" assertions. If you were to check the 
technical documentation a little further than the primer 
introduction, this would become obvious.

>To get a second opinion for the field of KR, I typed
>the following to Google:
>
>    ontology "knowledge representation"
>
>And the first hit was
>
>    http://www.cs.man.ac.uk/~stevens/onto/
>
>The text (copy below) defines the word in more detail,
>but still with the underlying idea that an ontology
>defines terms, as in the T-box, not assertions,
>as in the A-box.
>
>I completely agree with your statement:
>
>>  And frankly, I think it is foolish to not be willing
>>  to adapt to what is obviously the current term of
>>  choice used throughout the rest of the world, even
>>  to the point now where it is being used in journal
>>  and conference titles without comment or explanation,
>>  simply in order to identify a subdiscipline of
>>  computer science.
>
>So I typed both words "ontology" and "theory" into Google:
>
>    "ontology" -- 1,140,000 hits
>
>    "theory" -- 25,800,000 hits
>
>Clearly, the word "theory" is the current term of choice
>used throughout the rest of the world, even to the point
>now where it is being used everywhere without comment
>or explanation.

Oh, come, don't be silly. That word has many meanings outside its 
technical use in logic.

>
>John
>____________________________________________________
>
>What is an Ontology?
>
>Ontology is the study or concern about what kinds of things exist - 
>what entities or `things' there are in the universe [3]. The 
>computer science view of ontology is somewhat narrower, where an 
>ontology is the working model of entities and interactions either 
>generically (e.g. the Cyc ontology [4]) or in some particular domain 
>of knowledge or practice, such as molecular biology or 
>bioinformatics. The following definition is given in [5]:
>
>`An ontology may take a variety of forms, but necessarily it will 
>include a vocabulary of terms, and some specification of their 
>meaning. This includes definitions and an indication of how concepts 
>are inter-related which collectively impose a structure on the 
>domain and constrain the possible interpretations of terms.'
>
>Gruber defines an ontology as `the specification of 
>conceptualisations, used to help programs and humans share 
>knowledge' [6]. The conceptualisation is the couching of knowledge 
>about the world in terms of entities (things, the relationships they 
>hold and the constraints between them). The specification is the 
>representation of this conceptualisation in a concrete form. One 
>step in this specification is the encoding of the conceptualisation 
>in a knowledge representation language. The goal is to create an 
>agreed-upon vocabulary and semantic structure for exchanging 
>information about that domain. The specification or encoding of an 
>ontology will be explored in Section 5.
>
>The main components of an ontology are concepts, relations, 
>instances and axioms.

Exactly. If you can distinguish this from a 'module' or 'theory' at 
this level of precision, you have better eyesight than I have.

Pat

>A concept represents a set or class of entities or `things' within a 
>domain. Protein is a concept within the domain of molecular biology. 
>Concepts fall into two kinds:
>
>    1. primitive concepts are those which only have necessary 
>conditions (in terms of their properties) for membership of the 
>class. For example, a globular protein is a kind of protein with a 
>hydrophobic core, so all globular proteins must have a hydrophobic 
>core, but there could be other things that have a hydrophobic core 
>that are not globular proteins.
>
>    2. defined concepts are those whose description is both necessary 
>and sufficient for a thing to be a member of the class. For example, 
>Eukaryotic cells are kinds of cells that have a nucleus. Not only 
>does every eukaryotic cell have a nucleus, every nucleus containing 
>cell is eukaryotic.


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