Multi-Head Finite Automata: Data-Independent Versus Data-Dependent Computations

We develop a framework on multi-head nite automata that allows us to study the relation of parallel logarithmic time and sequential logarithmic space in a uniform and nonuniform setting in more detail. In both settings it turns out that NC 1 requires data-independent computations|the movement of the input-heads only depends on the length of the input|whereas logarithmic space is caught with data-dependent computations on multi-head nite state machines. This shed new light on the question whether these two classes coincide or not.