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For the sake of someone like me that lacks the rigour to readily read
your relational set notation, could you possibly restate the problem
at hand in English, which tends to be the language of choice of my
users (and me!)
Can you map this to a real world requirement, or is this an obtuse theoretical device that has little relevance to the everyday world of the programmer that you are trying to measure the productivity of, as your relationships would surely be part of the DBMS in the first instance (though become relevant in some environments when trying to optimise an arbitrary query against Rik(A,Aik)
"x" <x-false_at_yahoo.com> wrote in message news:<40854c6a$1_at_post.usenet.com>...
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>
> Periodical discussions about the relational model/DBMS versus PICK or object
> model/DBMS take place in this newsgroup.
> I have some training in the relational model, but none in object/PICK like
> DBMS.
> I would like to know which model/DBMS perform better (in terms of
> programmers productivity, system requirements, etc.) on the following
> problems (stated in terms of relational model) :
>
> 1)Been given the domains {A,A1,A2,...,An}, with large n and the following
> database schema:
> - for all i in 1..n, Ri(A,Ai) is a base relation
> - for all i in 1..n, A is a candidate key for the relation Ri
>
> answer the questions:
> a) 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.
> b) for a in A given, find R(A,Ai1,Ai2,...,Aip) with the constraints:
> - R(A,Aik) = Rik(A,Aik) for all k in 1..p
> - {Ai1,...,Aip} is maximal
> - R is minimal
>
> 2) 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:
> a) No NULLs are allowed
> b) R(X1,X2,...,Xp) is the projection of R on the attributes (X1,...,Xp)
>
>
>
>
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Received on Wed Apr 21 2004 - 01:28:10 CDT