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Type hierarchies are an integral part of the object oriented software reuse machinery. Software flexibility can be increased through type inheritance which, if used in accordance with Liskov Substitution Principle (LSP) enables safe object substitution.Assuming that formal specifications are available for a set of subtypes, we present our early doctoral research on the automatic inference of an extended deterministic finite automaton that describes the legal usage of abstract supertypes and ensures the behavioral subtyping relation as defined by the Liskov Substitution Principle (LSP). We obtain the supertype interface automata by incrementally exploring the specification of the subtypes, unifying correlated subtype fields, simplifying predicates through quantification, and finally creating new model fields that we associate with the remaining predicates.The inferred automaton is simulated by the behavior of each subtype and can be used for safe hierarchy extension, verification of new hierarchy clients, and emphasis of LSP non-compliant methods.

Several reengineering environments have been created to provide for a unified infrastructure in which various approaches can be employed together. While the collaboration between tools is very strong within such environments, currently the inter-environmental collaboration is very weak and happens mainly at the level of data-files exchange. Consequently, the different groups of researchers are only collaborating shallowly via data, rather than at the level of analysis. In this demo, we present NOREX, a distributed reengineering environment that allows different groups of researchers to transparently use and combine existing techniques, and share their own, transcending any parochial barriers (e.g., implementation language or environment).

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