1. A method, executed on a computing device, for using an expert system to recommend a customized solution for a customer, the method comprising: providing in the expert system a set of scenarios each of which includes default facts and is associated with a detailed rule base that when applied in isolation to the default facts fully determines a prototype solution; selecting a particular scenario from the set of scenarios based at least on user input, wherein the selecting comprises: posing at least one specific question to a user who is a representative of the customer and obtaining supplied facts from answers to the questions; in a context of the supplied facts, inferring facts from parseable input supplied to the expert system; determining a subset of the scenarios from the inferred facts and the supplied facts; and enabling the user to select a particular scenario from the subset of the scenarios; generating a customized solution by applying the detailed rule base associated with the particular scenario to a set of candidate facts that comprises the inferred facts, the supplied facts, and assumed facts, where the assumed facts are any default facts of the particular scenario that complement and do not conflict with the inferred facts and the supplied facts iteratively refining the customized solution; and presenting the user with the customized solution and with a log of the parseable input supplied to the expert system; and indicating to the user which of the candidate facts are most significant in determining the customized solution.