Directed Graphs

Question

Conisder the following piece of code :

cin >> a >> b;
int x,y,z;
x=0; y=1; z=1;
if (a > b){
x = a*b;
while (10 > a){
y=y+z;
a=a+5;
}
else {
x=x+b;
}

Its Directed graph is shown below :

Now the next figure is Annotated tokens showing the slices on which the tokens occur

Now from the above figure we can calculate many cohesion metrics ( for example weak functional cohesion) . My question is how did we transform the directed graph to this annotated diagram . In other words I can't understand this statement "Annotated tokens showing the slices on which the tokens occur" ?

Answer 1

Take a look at the output X (its on the bottom). The notation states that the X relies only on itself. Which makes sense: evaluate(X) == X.

One step up and you have the statement x = x b. Again evaluate(X) == X so the x on the left hand side of the assignment is self-explanatory. The x and b on the right of the assignment only influence x though, hence they influence the output token X. b is the input token B, so the input token also affects the outcome of X.

Now the input token B can also influence to output token Y. It does this by the (a > b) comparison being true. This executes extra code that modifies y. You can see this by the arrows. So while it does not appear in the expressions concerning y it none the less has an effect. Similarly for a and the output token A.

What this leaves us with is each symbol being annotated with the outputs it influences.

note: I've capitalised the input/output variables to differentiate for the intermediates as lower-case.