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ion Selection Specialization P1/A1 Pn/An S1/G 1 Sn/G n S/G P/A 8 Abstraction For each program P i (i=1, ... , n) we identify a program schema S i which describes P i abstractly. This abstraction generates a set of substitutions q i for schema variables. The same abstraction leads from the literals A i to the abstract literals G i . In short, the abstraction step replaces each term P i /A i by its abstraction S i /G i , and we have P i /A i = S i q i /G i q i . Selection Transformation schemata transform the set of abstract terms {S 1 /G 1 , ... , S n /G n } into an abstract term S/G, i.e. a transformation schema is defined as {S 1 /G 1 , ... , S n /G n, S/G}. In general there are several transformation schemata which have {S 1 /G 1 , ... , S n /G n } as input. We select the transformation schema which generates a desired output program schema S together with an abstract literal G. Specialization We apply the substitution q = q 1 ... q n to S/G to get the transformed pr...

We present a general strategy for stepwise, sound and progressive synthesis of logic programs from specifications by examples and properties. We particularize this to schema-guided synthesis, and state a generic synthesis theorem. We justify some design choices for the development of a particular synthesis mechanism that is guided by a Divide-and-Conquer schema, is inductive and deductive, is interactive, and features a non-incremental presentation of examples. Some crucial steps of this mechanism are explained, and illustrated by a sample synthesis. We draw some conclusions on our results so far, state some related work, and outline future research directions.

In our method -- that we call Visual and Textual Composition of Logic Programs -- we have enhanced the schema-based construction of logic programs in two ways intended to bridge the conceptual gap between application domains and the programming domain. First, we define visual and textual views of programs that can be used to construct programs in application-specific concepts, and which can be understood as executable specifications of the programs being constructed. Second, in addition to schemata for Prolog programming constructs and techniques we introduce a repository of application-specific components. As a further enhancement of the method we have added schema-based transformations to increase the efficiency of the constructed programs. We have implemented both a program development system and a transformation system, and used these systems to develop programs for non-trivial applications like the well-known library data base problem and an automated teller machine. 1 Schema-Base...