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Foundations of Data Exchange - download pdf or read online

By Arenas M., Barcelo P., Libkin L., Murlak F.

ISBN-10: 1107016169

ISBN-13: 9781107016163

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Finally, a tgd V (x1 , x2 , x3 ) ∧V (y1 , y2 , y3 ) → ∃zi j V (xi , y j , zi j ) 1≤i, j≤3 states that the function encoded by V is total. Indeed, this tgd says that if two elements a and b appear in the interpretation of V , then there must be an element c such that V (a, b, c) holds.

But others are possible too, for instance T = {ROUTES(⊥1 , Paris, Santiago), INFO FLIGHT(⊥1 , 2320, ⊥1, AirFrance)}, or even a solution with no nulls: T = {ROUTES(AF406, Paris, Santiago), INFO FLIGHT(AF406, 2320, 920, AirFrance)}. On the other hand, assume that M is the extension of M with the target dependency (an egd) stating that src is a key in ROUTES(f#,src,dest). Then it is no longer true that every source instance has a solution under M . Indeed, consider a source instance S = {FLIGHT(Paris, Santiago, AirFrance, 2320), FLIGHT(Paris, Rio, TAM, 1720)}.

2) The target schema Rt consists of the ternary relation ROUTES(flight#,source,destination) and the 4-ary relations INFO FLIGHT(flight#,departure time,arrival time,airline) and SERVES(airline,city,country,phone). (3) Σst consists of the following source-to-target dependencies: 36 The problem of relational data exchange FLIGHT(src,dest,airl,dep) −→ ∃f#∃arr (ROUTES(f#,src,dest) ∧ INFO FLIGHT(f#,dep,arr,airl)) FLIGHT(city,dest,airl,dep) ∧ GEO(city,country,popul) −→ ∃phone SERVES(airl,city,country,phone) FLIGHT(src,city,airl,dep) ∧ GEO(city,country,popul) −→ ∃phone SERVES(airl,city,country,phone).

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Foundations of Data Exchange by Arenas M., Barcelo P., Libkin L., Murlak F.


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