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KazaX
Starting Member
28 Posts |
 Posted - 2008-12-01 : 17:44:33
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| Hello!Have been stuck.... appreciate any idea...Consider three schemas T1, T2, T3:T1 = {G(A,B)}T2 = {G'(A,B),R(A,C)}T3 = {D(C1,C2)}Let M12 be the mapping from T1 to T2 given byG'(x, y) :– G(x, y)R(x, c1),R(y, c2) :– G(x, y)and let M23 be the mapping from T2 to T3 given byD(c1, c2) :– R(x, c1),R(y, c2),G'(x, y)what will composition mapping M13 from T1 to T3 look like?D(c1, c2) :– ?Cheera |
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tkizer
Almighty SQL Goddess
38200 Posts |
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KazaX
Starting Member
28 Posts |
Posted - 2008-12-01 : 19:46:02
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quote:
Originally posted by tkizer
I'm unable to decipher your issue. Could you put this into more general terms?Tara KizerMicrosoft MVP for Windows Server System - SQL Serverhttp://weblogs.sqlteam.com/tarad/Subscribe to my bloghi!Actually, it is obvious if u r aquainted with the term schema mapping in data integration and exchange. We have source relations and Target ones. We have data in source relations and some formalisms in transfering the data to target schemas, the formalisms are called mapping constraints. we have Sources (S1,S2,S3) there is a mapping S1 to S2 -M12 and S2 to S3- M23. The mapping rules are specified. We are asked to find composition mapping, namely M13 from S1 to S3 directly. For instance in "T1 to T2": We have target schema G'(x,y):-G(x,y) --this means we copy the source G(x,y) to target G'(x,y), this can alternatively denoted G(x,y)-->G'(x,y). Hope could explain
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sodeep
Master Smack Fu Yak Hacker
7174 Posts |
Posted - 2008-12-01 : 20:10:01
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| All of your questions resembles Set theory .You need to show relational theory with Cardinality, tuples and attributes so we can help you:http://www.sqlteam.com/forums/pop_profile.asp?mode=display&id=42717 |
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composition mapping