Heuristic search, theory

The set of candidate solutions considered by a search procedure is often called the search space of the problem. For molecular design problems, there are several possible search spaces, the most common being sequence space, the space of all molecules being considered [4,37-39], The concept of a sequence space is important because it provides a framework for formal theory and it has heuristic value in developing intuition for searches and communicating ideas. Sequence spaces are discrete, though search spaces in general may be discrete, continuous, or discrete on some axes and continuous on others. 

Concerning tactics, in many cases, heuristic devices or rules of thumb are used. For the intramolecular dynamics problem, low-order (meaning usually first-order) perturbation theory is frequently used in the tactical search. Imagine that we begin with state )) in tier t. This state has the zero-order energy ) . We compute the first-order coupling strength to the candidate state fc) in tier t + 1 ... 

ACM [22,23] is similar to CIRRUS. It is based on the theory that problem solving is search through a problem space. It takes as its model a specific problem space, and builds a set of operator selection heuristics that will cause search through this problem space to simulate answer data given to the program. 

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