% XY Example 3. BOM: for each part X counting its basic componets Y
% "Negation and Aggregates in Recursive Rules: the LDL++ Approach", DOOD 93.

database ( {
        g(X:string, Y:string, Q:integer)
}).

export rgc(I, X, Y, C).
export final_count(X,Y,C).

rgc(0,X,Y,sum_all<Q>)	<-	g(X,Y,Q), ~g(Y,_,_).
rgc(I+1,X,Y,sum_all<Q>) <-	g(X,W,Q2), rgc(I,W,Y,Q1), Q=Q1*Q2.

final_count(X1,Y1,sum_all<Q>) <- rgc(I,X1,Y1,Q).