Functional Dependencies .X->Y is an assertion about a relation R that whenever two tuples of R agree on all the attributes of X,then they must also agree on all attributes in set Y. Say "X->Y holds in R." Convention:...X,Y,Z represent sets of attributes;A,B, C,...represent single attributes. Convention:no set formers in sets of attributes,just ABC. rather than [A,B,C 44 Functional Dependencies z X ->Y is an assertion about a relation R that whenever two tuples of R agree on all the attributes of X, then they must also agree on all attributes in set Y. – Say “X ->Y holds in R.” – Convention: …, X, Y, Z represent sets of attributes; A, B, C,… represent single attributes. – Convention: no set formers in sets of attributes, just ABC, rather than {A,B,C }