Given functions f:A→B and g:C→D with ran(f)C we can define a third function called the composite function from A to D.(We will usually call this the composition,rather than the composite function.)This composition is the function g of:A-D defined by (gof)(x)=g(f(x)). Let R be a relation from A to B and S be a relation from B to C.Then we can define a relation,the composition of R and S written as SoR.The relations SoR is a relation from the set A to the set C and is defined as follows: If aA,and c A,then (a.c)SoR if and only if for some be B.we have (a,b)R and (b,c)eS. 间题7：这两个定义有什台关联？有区别吗？