Syntax, Semantics and In Between
Dmitry Gaivoronsky
Из блога John'а De Oliveira - одного из разработчиков Cyc.
http://johndcyc.blogspot.com/2006/04/syntax-semantics-and-in-between.html
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*Syntax, Semantics and In Between*
I'm about to post a response to a comment I received about Thursday night's
presentation, but first I want to define some terms. (The fact that I have to
try to establish this common ground vocabulary in order to discuss these issues
ironically argues my point for me, as I hope you'll see in the next post.) I
invite corrections to my naive definitions, as long as the corrections can be
stated in something close to English.
*Syntax* is expressed by the simple grammar rules you get in any computer
language. (If you want to be more technical, I'm talking about the kind of
simple prescriptive grammars that can be defined with _BNF_
[http://en.wikipedia.org/wiki/Backus-Naur_form].) OWL and CycL also have a
syntax that can be defined with simple grammar rules.
*Vocabulary* is an agreed upon set of terms. There may be an implied connection
to the things in the world the terms refer to ("clock" is a device we use to
tell time), but it is not required that the terms be interrelated in any way.
OWL intentionally has a quite small vocabulary. Vocabularies are handled by a
proliferation of OWL ontologies. _Electronic Data Interchange_
[http://en.wikipedia.org/wiki/Electronic_Data_Interchange] (EDI) has a _large
vocabulary_ [http://www.x12.org/] of business terms. Cyc currently has a much
smaller business vocabulary that EDI. It is also smaller than the sum of the
vocabularies in OWL-based ontologies. Cyc has a very large vocabulary of terms
that refer to things in the everyday world.
*Ontology* is a formal set of statements, built from a vocabulary, and about
the things that the vocabulary terms refer to in the world. If we have a
vocabulary that includes "dog" and "mammal", an ontology made from that
vocabulary would have a statement that the set of all dogs (referred to by the
vocabulary term "dog") is a subset of the set of all mammals (referred to by
the vocabulary term "animal"). More simply, a dog is a kind of animal.
Finally, *semantics* (for the purposes of comparing knowledge representation
choices) refers to the meanings of statements ("Your mother's brother is your
uncle.") expressed in a form suitable for logical manipulation: (implies (and
(mother ?X ?M) (brother ?M ?B)) (uncle ?X ?B)). I argue that an important
distinction can be made between support for semantics and semantics. OWL has
support for semantics (and a small amount of actual semantics involving the
language primitives), and every related ontology adds to the actual semantics
expressed using OWL. Cyc contains the support for semantics as well as the
ontology content that gives it actual semantics. Cyc is compatible with OWL and
can extend its semantics the semantics of OWL in the same way that any other
ontology can.
posted by #$JohnD @ 9:45 PM Saturday, April 15, 2006
0 comments
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Sayonara... Dmitry.