In most cases, the line of embusen (direction of performance, or line of attack) of a kata is the same as the direction of movement. However you run into some cases where it's not so clear, and it seems to be where you get interesting applications. For example the end of pinan sandan. I was explicitly taught that I should be looking over my shoulder behind me (both in shotokan and in shito-ryu), with the implication that the line of embusen continued to be to the rear, however the body movement is lateral at this particular point and if you look at most embusen diagrams they indicate the direction of movement, in fact most just indicate the shape of the kata rather than vectors pointing a direction.
Looking at youtube performances for this particular kata it seems pretty hit or miss whether people look over their shoulders. Some look in the direction of movement, some look to the front.
Any thoughts? Particularly on head position indicating the line of embusen where it differs from the direction of movement. What were you taught?