Hierarchical Defaults in Speciications
نویسندگان
چکیده
The goal of this paper is to explain the usage and semantics of hierarchical defaults in logical speciications. We discuss the usefulness of defaults for diierent speciication scenarios like specialization, aggregation, explanation, revision, etc. To understand defaults formally, we introduce a general framework parameterized on the underlying logical institution extended by an instantiation mechanism for formulae. It is shown that hierarchical defaults have intended models if the extended institution is compact. As an example for a non-standard logic, we give the semantics of defaults in the multi-modal object calculus of the is-core project. To structure and compose speciications with defaults, default-preserving speciication morphisms are deened and corresponding colimit constructions are sketched.
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