26. A software shell as claimed in claim 25 wherein the means for determining includes means for receiving input data, determining when knowledge source execution preconditions are met, and checking only a knowledge source whose execution preconditions are met for execution availability.
26. A software shell as claimed in claim 25 wherein the means for determining includes means for receiving input data, determining when knowledge source execution preconditions are met, and checking only a knowledge source whose execution preconditions are met for execution availability. 27. A software shell as claimed in claim 26 further including: a blackboard structure description file including object names and attribute/value pairs for each object; a rule-based description file including rules forming the rule-based knowledge source and a description of execution preconditions for the rule-based knowledge source; and a case-based description file including cases forming the case-based knowledge source and a description of execution preconditions for the case-based knowledge source; wherein the blackboard structure description file, rule-based description file, case-based description file, and input data file are user created.