Data Dependency

Data dependency reveal how the value of the variable is assigned during the program execution

int a = 1; // Step 1
int b = a + 1; // Step 2
int c = a + b; // Step 3

From the above example

• Variable c is defined by variable a and b, making Step 1 and Step 2 is the data dominator of Step 3.
• Variable b is defined by variable a, making Step 1 also the data dominator of Step 2.

Control Dependency

Control dependency indicate relation between condition predicate and the branch of steps executed

boolean condition = true; // Step 1
if (condition) {  // Step 2
    function1();  // Step 3
} else {          
    function2();  // Step 4
}

Variable condition determine which code is executed (i.e. Step 3). So that Step 2 is the control dominator of Step 3.

Back Tracing

Back tracinig is the technique of debugging. Starting from output program, if we trace back via data and control dependency, we can eventually find out the root cause of the bug.