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Re: [ontolog-forum] Ontology and Databases

To: <matthew.west@xxxxxxxxx>
Cc: ontolog-forum@xxxxxxxxxxxxxxxx
From: Pat Hayes <phayes@xxxxxxx>
Date: Tue, 24 Oct 2006 11:41:23 -0500
Message-id: <p06230912c163ee9d011c@[]>
>Dear Antoinette,
>Well I think this is only part of what you need to look at. Logic
>based ontology languages have elements that are both classes and
>instances.    (01)

Not all of them, and in fact the DL folk argue 
strongly against this. OWL-DL for example 
prohibits classes as instances, though they have 
work-arounds to handle some tricky cases. Common 
Logic is of course totally unrestricted in this 
regard, and allows anything. In CL, a class can 
be an instance of itself (example: rdfs:Class in 
RDFS).    (02)

>When you translate that into a database, the instances
>become database records. Therefore there is a key design decision
>about what in your ontology to have in the database structure, and
>what to hold as data.
>Apart from that, and looking at what Chris mentions below, my
>experience is that different languages have different capabilities
>and limitations, and you need to first of all look at the limitations
>in your source format, and try to make sure when you translate, not
>to introduce the unintended limiations from the first language in
>the second.    (03)

Amen to that :-)    (04)

>PS. Note to Chris on contradictions:
>Data models are ontologies    (05)

Really?? Matthew, what IS a 'data model', exactly?    (06)

>Common Logic has a Data Model    (07)

There is a formalization of CL *syntax* in a 
'datamodelling' formalism. I'm sure this will be 
useful to someone, but it really is only useful 
for parsing CL, not for interpreting it. It is a 
description of a class of labelled tree 
structures, in fact. Seems to me this is about 
the same information that you would have by 
simply writing CL in XML, just expressed in a 
different formalism.    (08)

>Therefore Common logic is NOT an ontology???    (09)

As I understand it, an ontology is, or is 
semantically equivalent to, a particular logical 
theory of something. CL is not a logical theory 
of anything, its the logic (more properly, the 
abstract logic) in which an ontology can be 
written. Now, you could imagine having an 
ontology of CL syntax, where the actual topic was 
the syntax. That would be like the data model 
mentioned above, but re-construed as an ontology. 
But (a) this doesnt seem very interesting, (b) it 
doesn't make the logic itself into an ontology, 
only its syntax, and (c) in fact, its not easy to 
do. There are some technical problems connected 
with how to represent recursively defined 
structures in an assertional logic. You could do 
it in CL, just, and awkwardly, because CL extends 
strict FO logic (by the sequence marker 
construction) but you couldn't do this in strict 
first-order CL (i.e. in a "compact dialect").    (010)

Pat    (011)

>>  -----Original Message-----
>>  From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>>  [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx]On Behalf Of Arsic,
>>  Antoinette
>>  Sent: 20 October 2006 17:05
>>  To: [ontolog-forum]
>>  Subject: Re: [ontolog-forum] Ontology and Databases
>>  Yes, that better rephrases my question.
>>  Thanks,
>>  Antoinette
>>  ------------------------------
>>  Antoinette Arsic , Information Scientist, M.S.
>>  The MITRE Corporation
>>  703-983-5286 (office)
>>  443-567-2703 (cell)
>>  -----Original Message-----
>>  From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>>  [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of
>>  Christopher Menzel
>>  Sent: Friday, October 20, 2006 11:44 AM
>>  To: [ontolog-forum]
>  > Subject: Re: [ontolog-forum] Ontology and Databases
>>  On Oct 19, 2006, at 6:48 AM, Arsic, Antoinette wrote:
>>  > I'm in desperate need of knowledge on how to move from an ontology 
>>  > to a
>>  > data model or how to develop the two together - I'm in a position 
>>  > where
>>  > we are developing the ontology and data model simutaneously (uggh),
>>  > just because that is how it has to be.
>>  I'm not sure I understand the question.  From a logical point of 
>>  view, a well-defined data model just *is* a type of ontology.  So, 
>>  from that perspective, to develop a data model is to develop an 
>>  ontology.  I'm suspecting therefore that your question has to
>  > do more 
>>  with how to express the same ontology (in the logical sense) in both 
>>  a specific data modeling language like ER and a specific ontology 
>>  language like OWL-DL.  Is that your question?
>>  Chris Menzel
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>    (012)

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