Re: [ontolog-forum] Simplifying the language and tools for teaching and

[William Frank <williamf.frank@xxxxxxxxx>]

On Fri, Jan 4, 2013 at 3:04 PM, Matthew West <dr.matthew.west@xxxxxxxxx> wrote:

Dear John,

You seem to be reading selectively.

 

JS: I believe that the failure to clarify that distinction and observe it consistently is the source of the disagreements.
 
>> On Mon, December 31, 2012 21:14, William Frank wrote:
>> ...
>> But what seems to me to be most fundamentally wrong in this
>> discussion
>>  is the notion that there is a good reason to define 'kind of
>> activity' separately from 'kind of stone' or kind of hope'.

JS: If Activity, Stone, and Hope, are categories (or classes or types) in your ontology, then you only need two metalevel terms:  'instance of' and 'subtype of' (or 'subclass of').

MW: As I explained, this does not work with a data model where you want to be able to extend your ontology in data, in particular being able to add subtypes as data instead of changing the data model by adding entity types each time you identify something new. Changing data models is expensive compared to changing data. You therefore need the entity type that the subtypes of e.g. activity would be instances of, and this is class_of_activity (or activity_type whatever your taste is).

So, perhaps defining class_of_activity as a special kind of class *is* peculiar, but useful, as a way to get run-time subclasses in a relational database.   
Perhaps I was misunderstanding your models as intended to be optimal for understand and formalizing the ontology of a domain of human endeavor,
while instead they are intended to optimally support that understanding in a way that can be used in a given kind of technology.  A way to avoid the 'impedence mismatch' between classes or E/R entity types and relational tables.   
 
As below:

MW: Well I wish you luck when you are working for a client and saying every time they want a new category they have to change the data model rather than adding a data record.

This is indeed a problem, I can see how this might be a very good solution.  I think there is more than one solution to it. 

 

Regards

 

Matthew West                           

Information  Junction

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-- 
William Frank

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