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24-DeducDatabases

# 24-DeducDatabases - Discussion#24 Deductive Databases...

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Discussion #24 Deductive Databases 1/21 Discussion #24 Deductive Databases

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Discussion #24 Deductive Databases 2/21 Topics Deductive Databases Turning Datalog into Relational Algebra Recursive Rules & the Least Fixed Point Algorithm
Discussion #24 Deductive Databases 3/21 Deductive Databases Deductive database management systems answer queries based on methods related to proofs from rules and facts. Relational algebra operations can be used to more efficiently process deductive database queries.

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Discussion #24 Deductive Databases 4/21 Correspondence Between Relational Databases & Deductive Databases Schemes: f(A,B) b(C,D) Facts: f(1,1). f(1,2). f(2,3). Rules: b(x,y) :- f(y,x). b(x,y) :- f(x,z),f(z,y). Queries: b(1,x)? f(A, B) b(C, D) 1 1 1 2 2 3 b b ρ x C ρ y D π xy ( ρ A y ρ B x f ) b b ρ x C ρ y D π xy ( ρ A x ρ B z f | × | ρ A z ρ B y f) π x ρ D x σ C=1 b
Discussion #24 Deductive Databases 5/21 Correspondence Between Relational Databases & Deductive Databases Schemes: f(A,B) b(C,D) Facts: f(1,1). f(1,2). f(2,3). Rules: b(x,y) :- f(y,x). b(x,y) :- f(x,z),f(z,y). Queries: b(1,x)? f(A, B) b(C, D) 1 1 1 1 1 2 2 1 2 3 3 2 b b ρ x C ρ y D π xy ( ρ A y ρ B x f ) b b ρ x C ρ y D π xy ( ρ A x ρ B z f | × | ρ A z ρ B y f) π x ρ D x σ C=1 b

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Discussion #24 Deductive Databases 6/21 Correspondence Between Relational Databases & Deductive Databases Schemes: f(A,B) b(C,D) Facts: f(1,1). f(1,2). f(2,3). Rules: b(x,y) :- f(y,x). b(x,y) :- f(x,z),f(z,y). Queries: b(1,x)?
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