Send a message requesting information, or receive a message and place the information at the front of short term memory. Place an item into short term memory. In each cycle, tests are evaluated sequentially. Problem should lend itself to a modular solution. Solution should be based more on declarative than procedural knowledge.
All knowledge is represented using the same kind of rules in the same kind of format.
In theory, each rule is independent. Allows well-defined and almost unrestricted communication between pieces of knowledge. Natural way to represent many kinds of knowledge. Opaqueness, unexpected interactions. Difficult to design.