1. Expert systems are information systems which use information about a specific area (usually consisting of highly complex issues) to serve as an expert consultant to users. Typically, expert systems contain a knowledge base and various modules which build on the information supplied by users to arrive at solutions or provide additional information. Decision support systems use decision models and databases to reach a specific decision using a predefined set of rules. An expert system might be used by physicians to help arrive at a diagnosis for a patient whose symptoms are not clearly indicative of any one illness, while a decision support system might be used by a manager to determine whether to buy or lease new equipment. In the first case, the physician would enter the various symptoms based on questions supplied by the expert system. The questions which are asked vary with the answers given, and various diagnoses are ruled out. In the case of the decision support system, the user enters predefined parameters (interest rates, required rate of return, purchase cost and so forth) and the decision support system process the information and renders a decision.
2. Effectiveness is whether or not a particular decision or action achieves the desired result. Efficiency is whether a particular result is achieved with the best use of resources. For example, a data entry clerk who has a stack of invoices to enter into a system is effective if all of the invoices are entered correctly. Clerks who are unable to complete this task, or who have a large number of errors, would be deemed ineffective.
Efficiency, on the other hand, relates to the way in which the task is performed. Some clerks will simply enter all of the invoices in order and quickly, while others might enter a handful, take a break, alphabetize the remaining invoices, resort them by numerical order, or perform other tasks which are not critical to the primary goal...