Hi, say we have entities A,B,C in a Relational Database. Is there a sort-of operational algebra that allows us to determine that if, say, A and B are in a many-many relation and B and C are in a 1-many relation, then A,C are in a certain relationship, i.e., a composition algebra between relations (whenever "composable", of course)? And, while we are at it, when are relations "composable" (in a formal way, ignoring semantic issues of whether the composition is meaningful) , meaning if A is related to B and B to C, can we say A is related to C? Any Mathematical Analogies more than welcome. Thanks.