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Greater concept

From The Concept-Oriented Portal
Revision as of 14:38, 15 May 2009 by Savinov (Talk | contribs)

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A greater concept is specified as a type of this concept dimensions. Thus a concept has as many greater concepts as it has dimensions (fields).

This concept in this case is called a lesser concept. A concept has as many lesser concepts as it is used as a dimension type in other concepts.

For example, if concept Person has a dimension of type Address (where this person lives) then Address is a greater concept while Person is a lesser concept:

   CONCEPT Address // Greater concept 
       IDENTITY 
           CHAR(3) addrId 
       ENTITY 
           CHAR(256) address 
   
   CONCEPT Person // Lesser concept 
       IDENTITY 
           CHAR(3) persId 
       ENTITY 
           CHAR(256) name 
           Address address // Points to a greater concept 

Thus concept dimensions (fields) play a very important role in the concept-oriented model because they allow us to establish a partial order among concepts (and their instances as a consequence). This feature is unique for COM and distinguishes it from other models. It is precisely why we say that COM relies on the theory of ordered sets. In particular, this ordering is then used to define two main operations: projection and de-projection.

Example

Let us assume that each employee (concept Employee) belongs to one department (concept Department) and each department has one manager (concept Manager):

   CONCEPT Manager 
       IDENTITY 
           CHAR(8) managerId 
       ENTITY 
           ... 
   
   CONCEPT Department 
       IDENTITY 
           CHAR(8) deptId 
       ENTITY 
           Manager manager // Points to greater concept 
   
   CONCEPT Employee 
       IDENTITY 
           CHAR(8) empId 
       ENTITY 
           Department department // Points to greater concept 

From this definition we see that concept Employee is a lesser concept of concept Department because it references it in its dimension department. Concept Department is a greater concept of concept Employee but it is a lesser concept of concept Manager because it references it in its dimension manager.

See also

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