On formal HAS-A definition
Date: Tue, 4 May 2010 14:21:49 -0700 (PDT)
Message-ID: <0b0623a8-7a8c-476b-8de2-78c31a36ab17_at_f17g2000pra.googlegroups.com>
Again, I didn't research literature, but here is my shot: the HAS-A is an inclusion dependency. Example:
Dept = [DeptNo DeptName]
Emp = [DeptNo EmpName]
10 Accounting
20 Research
;
10 King
10 Smith
;
Formally:
Emp v (Dept ^ []) < Dept v (Emp ^ []).
I suppose HAS-A shares many unconvenient properties with set
membership, for example, it is not transitive. Consider
Accounts = [EmpName Institution]
the it is not the case that "Dept HAS-A Accounts". Again, the naming
problem raises its ugly head: why would the first attributes be called
Smith BoFA
Smith WellsFargo
;
More important: is this correct formalization? Specifically, shouldn't functional dependency
Dept # DeptNo < Dept # DeptName
be a part of HAS-A constraint definition? Received on Tue May 04 2010 - 23:21:49 CEST