If the rule has never visited Y, however, then such an exit arc is not considered a valid candidate. Lambda Graphs Lambda abstraction is a powerful form of referring to non-numeric calculatory items such as functions and, in the case of Tamerlane, graphs. Y Y is like a 'local variable' in this respect. When the rule is applied to the node, and the pattern match succeeds, the nodes named Y and Z need not actually exist, as they are simply created dynamically and 'attached' to the program graph. Lambda graphs are subject to garbage collection, since they can only be used by the rule that created them.
Pigeonholes acknowledge events.
Their assignment is associated with both nodes and arcs. Horn Rules Horn rules only succeed if all of their rules succeed. Note also that arcs are unordered amongst themselves.