# Relational vs. PICK/Object DBMS

From: x <x-false_at_yahoo.com>
Date: Wed, 21 Apr 2004 10:04:13 +0300
Message-ID: <40861c4a\$1_at_post.usenet.com>

Sorry for the omissions/errors in the previous post.

1)Been given the domains {A,A1,A2,...,An}, with large n and the following  database schema:

1. for {i1,i2,...,ip} given , find R(A,Ai1,Ai2,...,Aip) with the constraints R(A,Aik) = Rik(A,Aik) for all k in 1..p, R is minimal.
2. for a in A given, find R(A,Ai1,Ai2,...,Aip) with the constraints:
• R(A=a,Aik) = Rik(A=a,Aik) for all k in 1..p
• {Ai1,...,Aip} is maximal
• R is minimal
3. Let P(A) be the power set of domain A for any domain A. Been given the domains {A,B,C} and the database schema R1(P(A),P(B)), R2(P(B),P(C)) answer the question: find R(P(A),P(B),P(C)) with the contstraints:
• R(P(A),P(B))=R1(P(A),P(B))
• R(P(B),P(C))=R2(P(B),P(C))
• R minimal

Note:

1. No NULLs are allowed
2. R(X1,X2,...,Xp) is the projection of R on the attributes (X1,...,Xp)
3. R(X1=a,X2,...,Xp) is the projection of R on the attributes (X1,...,Xp) followed by the selection upon X1=a (or viceversa)
4. R1(P(A1),P(A2), ..., P(Ap))=R2(P(A1),P(A2),...,P(Ap)) iff
• for any (X1,...,Xp) in R1, for any (x1,...,xp) in X1xX2,...xXp there is an (Y1,...,Yp) in R2 such that (x1,...,xp) is in Y1xY2x...xYp
• for any (Y1,...,Yp) in R2, for any (y1,...,yp) in Y1xY2,...xYp there is an (X1,...,Xp) in R1 such that (y1,...,yp) is in X1xX2x...xXp
5. for any R(P(A1),P(A2),...,P(Ap)), for any two distinct (X1,X2,...,Xp) , (Y1,Y2,...,Yp) from R, X1x...xXp /\ Y1x...xYp is void where /\ stands for intersection and x for cartesian product.
6. A maximal (minimal) means A has a maximal (minimal) number of elements.

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Received on Wed Apr 21 2004 - 09:04:13 CEST

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