Comparison

Efficiency. Choosing the type of analysis (top down or bottom-up) depends on the configuration tree, which carried out a search. If, on average, each element should be a larger number of elements, rather than precede, the analysis of top-down (or the reverse analysis) would be more effective and vice versa. Consider the extreme case. Assume that the search area forms a tree with a vertex in the initial state. Then, using the direct approach, we will have to search for virtually the entire tree, while the opposite approach - only in its linear part.

Comparison and unification. In systems with a set of logical rules, or systems analysis to select direct or reverse the chain of analysis affects the degree of difficulty of the comparison. A direct chain analysis of the system is constantly subject to new facts that have no free variables. Thus constantly compares the background, it is likely with free variables, with the facts that do not have such.

On the other hand, systems with a backward chain analysis of the honor of asking specific questions. If the rules are set out in the logic of predicates and not the logic of judgments, then a comparison is made between the question of variable in the investigation of variables. Secondary queries can contain variables, so in general the system with the opposite chain analysis should be designed in such a way that they could compare two character structures, each of which can contain variables, which would require the creation of an algorithm unification.