Heuristic Synthesis from Examples

Heuristic synthesis from examples involves more or less heavy use of heuristics in order to prune the search space. 

Heuristic synthesis from examples is performed by the systems of [Hardy 75], [Shaw et al. 75], [Siklossy and Sykes 75], and [Biggerstaff 84], in the sense that they fill in the place-holders of a LISP divide-and-conquer schema (see Chapter 8) in a plausible way according to the given examples. 

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Example 14.5. Use evolutionary synthesis to seek an improvement to the sequence that was developed from heuristics in Example 14.4. 

Figure 7.12 Synthesis problem and separation train for Example 7.2 (a) paraffin separation problem (b) sequence developed from heuristics.

Choice of Process Configuration. The sequence of processing steps and flowsheet configuration must be selected concurrently with the choice of extraction chemistry. Some of the established heuristics of separation process synthesis may be helpful here. For example, in multimetal fractionation it is probably better to tiy selective stripping from a single organic stream than to do multiple selective-extraction oper-... 

Task A is done in the same fashion as in manual logic algorithm construction [Deville 90] (see Section 4.2) the induction parameter must be simple, and of an inductive type. This selection can be automated by type inference from the given examples. In case more detailed specification knowledge is available, the Functionality Heuristic (Heuristic 4-1) and the Directionality Heuristic (Heuristic 4-2) may even be used, the latter being of higher precedence in case they yield contradictory results. A reasonable implementation of this synthesis mechanism would actually even accept preference hints from the specifier. We assume that the parameter is selected as induction parameter, where [Pg.162]

The degree of automation depends on the actual implementation of the synthesis mechanism. Indeed, as it stands, the mechanism is fully automatable. However, there are critical points where interaction with the specifier is safer than blind application of the listed heuristics, however reliable they may seem. The synthesis mechanism is example-driven, and uses the properties at selected moments. This implies that synthesis cannot be done from properties alone. On the other hand, if only examples are provided, or if not enough properties are provided, then there should be a lot of interaction with the specifier. 

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