ACME is a mapping engine based on the theory that mapping is a result of structural, semantic, and pragmatic constraints (Holyoak & Thagard 1989b). Structure, in this sense, is does not necessarily mean a physical makeup, but the nature of the representation: elements are structurally similar if they share the same relational structure with other elements. Semantic similarity means elements are either identical symbols or share predicates (e.g. a common super ordinate). Pragmatic constraints involve relative importance of some propositions in the representation given the goals of the agent. The mapping is generated as a result of a constraint-satisfaction spreading activation network. Transfer in ACME involves transferring relations and postulating new elements from the source analog, but it does not have a mechanism for the transfer of a solution procedure. That is, it is made to transfer facts, not instructions.