To summarize the iTech approach to recommending the next-best-test:

1. which is the quickest test (time)

2. in the area with the highest probability of failure (probability)

3. that will eliminate as close to half the remaining suspect components as possible (split-half reasoning)

of course the logical chaining of components in the model covers the forward and backward chaining methods.

So iTech actually combines all the traditional methods into one optimized method which includes the MOST important factor TIME!

Of course you may also optimize by cost rather than time, if cost is more important.