%
% Understanding Relational Database Query Languages, S. W. Dietrich, Prentice Hall, 2001.
%
%---------------------------------------------------------------------------------------------------------------------------
%        DRC By-Name (DBN)
%---------------------------------------------------------------------------------------------------------------------------
%  Abstract Division Example
%
%  abTable(a,b)
%       primary key (a, b)
%  bTable(b)
%       primary key (b)
%---------------------------------------------------------------------------------------------------------------------------



universalDivision(a: A) <- abTable(a:A) and 

  (forall B) (not bTable(b:B) or abTable(b: B,a: A)); 



forallExistsEquivalence(a: A ) <- abTable(a:A) 

  and not (exists B) (not (not bTable(b:B) or abTable(a:A,b:B)));



existentialDivision(a: A) <- abTable(a:A) 

  and not (exists B) (bTable(b:B) and not abTable(a:A,b:B));