I'm new to sudoku and until yesterday I was under the impression that Nishio techniques in sudoku are just picking a candidate at random, then trying to solve the puzzle. Then yesterday I saw at sudokuwiki.org that Nishio is actually a chaining technique and realized it similarity to weak linked discontinuous NICE loops. In my opinion, finding NICE loops and all other similar alternating inference chains (x cycles, xy chains, forcing chains etc.) with exception to the Nishio chain are valid sudoku solving techniques because they use logic to find , and that these techniques do not assume a candidate to be true.

My question is this. In your opinion, do you consider Alternating Inference Techniques to be valid sudoku solving techniques? If not, what techniques do you consider valid, considering that many of the other patterned based techniques are chains themselves?