JessWorkings

• JESS's purpose it to continuously apply a set of if-then statements, called rules, to a set of data, called the fact list.
• In a typical expert system a fixed set of rules is used, but the fact list changes continuously. However, it is an empirical fact that in most expert systems, much of the fact list is also fairly fixed; although new facts are arriving and old ones being removed at all times, the percentage of facts that change per unit time is generally fairly small.
• JESS implements the Rete (Latin for "net") algorithm ("Rete: A Fast Algorithm for the Many Pattern/ Many Object Pattern Match Problem", Charles L. Forgy, Artificial Intelligence 19(1982), 17-37)
• Rete algorithm is implemented by building a network of nodes, each of which represents one or more tests found on a rule LHS. At the bottom of the network are nodes representing individual rules. When a set of facts filters all the way down to the bottom of the network, it has passed all the tests on the LHS of a particular rule and this set becomes an "activation".

		[JessIntroduction | JessAndAgents | ReteExample]