Robert,
 
ISO 1087-1 and ISO 704, which are standards for creating vocabularies and definitions (and did not arise from a formal logic community), specify two  mechanisms
 for defining a ‘concept’ or ‘class’:
  1) identify a more general concept and the delimiting characteristics of the subordinate concept being defined
    This is exactly:  An A is a B that C.
2) identify a list of subordinate concepts that together cover the more general concept being defined – the union of other defined classes:
    An A is a B or a C or a D.
 
One can also define a Class as the intersection of two or more classes, but that is just a special case of (1):  An A is a B that is also a C.
 
I’m not aware of any others.
 
-Ed
 
From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx]
On Behalf Of rrovetto@xxxxxxxxxxx
Sent: Saturday, June 21, 2014 9:32 PM
To: [ontolog-forum]
Subject: [ontolog-forum] Types of Formal (logical) Definitions in ontology
 
 
 
1) How many types of formal (logical) definitions of terms/classes do you know of?
 
For example, a term can be defined in a genus-species form: 
An A is a B that C.
What others do you know of?
 
2) For ontologies, are there non-FOL definitions?
Are there definitions not based on syllogistic logic?
 
3) And what are the pro's and con's of each?