A variety of mechanisms for producing directional orientations have been proposed in the literature. Two serial approaches are the Perfect Grid Rules of Prince (1983) and the Parametric Foot Construction approach of Hayes (1995). The Perfect Grid Rules are implemented in a grid-only framework. They construct the metrical grid entry by entry working either from left to right or from right to left. The Parametric Foot Construction Rules perform a parallel function in a foot-based framework. They build feet from syllables one at a time working either from left to right or from right to left. In a parallel approach like Optimality Theory, the grammar cannot create structures step by step. It cannot start at one edge and work towards the other. Alignment constraints allow parallel approaches to reproduce the directional effects of the earlier serial approaches. Alignment constraints accomplish this by discouraging misalignment between domain edges. Distance-sensitive Alignment takes degree of misalignment into account. It assesses a greater number of violations as the degree of misalignment increases. Distance-insensitive Alignment does not take degree of misalignment into account. It assesses the same single violation for each instance of misalignment, regardless of degree.