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Re: [ontolog-forum] brainwaves (WAS: to concept or not to concept, is th

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Thu, 13 Dec 2007 23:15:54 -0500
Message-id: <4762037A.4070809@xxxxxxxxxxx>
Pat,    (01)

That kind of connection is very common in databases and
knowledge bases.  I agree that some way of describing it
clearly and simply would be useful.    (02)

But I agree with Chris that using the term "existential
qualifier" is confusing.  Some people use the term
"dependent entity", but that is also confusing, because
it would imply that any talk about a child would introduce
the two parents as "depedents".    (03)

There is, however, a common term in database theory:    (04)

    functional dependency.    (05)

In a relational database, for example, some columns of a table
might be "functionally dependent" on other columns.  For an
employee relation, the columns for manager, department, and
salary are functionally dependent on the employee.  That
means, for any employee x, there are functions f1, f2, f3,
such that    (06)

   f1(x) is the manager of x    (07)

   f2(x) is the department of x    (08)

   f3(x) is the salary of x    (09)

I suggest that we use the term "functional dependency"
for such entities.    (010)

John    (011)

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