Structure mapping engine

In artificial intelligence and cognitive science, the structure mapping engine is an implementation in software of an algorithm for analogical matching based on the psychological theory of Dedre Gentner. The basis of Gentner's structure-mapping idea is that an analogy is a mapping of knowledge from one domain (the base) into another (the target). The structure-mapping engine, or SME, is a computer simulation of the analogy and similarity comparisons.

As of 1990, more than 40 projects had used it [Falkenhainer, 2005]. R.M. French said that structure mapping theory is "unquestionably the most influential work to date of the modeling of analogy-making" [2002].

The theory is useful because it ignores surface features and finds matches between potentially very different things if they have the same representational structure. For example, SME could determine that a pen is like a sponge because both are involved in dispensing liquid, even though they do this very differently.

Structure mapping theory is based on the systematicity principle, which states that connected knowledge is preferred over independent facts. Therefore, the structure mapping engine should ignore isolated source-target mappings unless they are part of a bigger structure. The SME, the theory goes, should map objects that are related to knowledge that has already been mapped.

The theory also requires that mappings be done one-to-one, which means that no part of the source description can map to more than one item in the target and no part of the target description can be mapped to more than one part of the source. The theory also requires that if a match maps subject to target, the arguments of subject and target must also be mapped. If both these conditions are met, the mapping is said to be "structurally consistent."

SME maps knowledge from a source into a target. SME calls each description a dgroup. Dgroups contain a list of entities and . Entities represent the objects or concepts in a description — such as an input gear or a switch. Predicates are one of three types and are a general way to express knowledge for SME.

Functions and attributes have different meanings, and consequently SME processes them differently. For example, in SME’s true analogy rule set, attributes differ from functions because they cannot match unless there is a higher-order match between them. The difference between attributes and functions will be explained further in this section’s examples.

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