Fibrational Induction Rules for Initial Algebras

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Patricia Johann Ph.D, Professor (Creator)
Institution
Appalachian State University (ASU )
Web Site: https://library.appstate.edu/

Abstract: This paper provides an induction rule that can be used to prove properties of data structures whose types are inductive, i.e., are carriers of initial algebras of functors. Our results are semantic in nature and are inspired by Hermida and Jacobs’ elegant algebraic formulation of induction for polynomial data types. Our contribution is to derive, under slightly different assumptions, an induction rule that is generic over all inductive types, polynomial or not. Our induction rule is generic over the kinds of properties to be proved as well: like Hermida and Jacobs, we work in a general fibrational setting and so can accommodate very general notions of properties on inductive types rather than just those of particular syntactic forms. We establish the correctness of our generic induction rule by reducing induction to iteration. We show how our rule can be instantiated to give induction rules for the data types of rose trees, definite hereditary sets, and hyperfunctions. The former lies outside the scope of Hermida and Jacobs’ work because it is not polynomial; as far as we are aware, no induction rules have been known to exist for the latter two in a general fibrational framework. Our instantiation for hyperfunctions underscores the value of working in the general fibrational setting since this data type cannot be interpreted as a set.

Additional Information

Publication
Neil Ghani, Patricia Johann, and Clement Fumex (2010) "Fibrational Induction Rules For Initial Algebras". Proceedings, Computer Science Logic (CSL'10), pp. 336 - 350. Version Of Record Available At www.springer.com
Language: English
Date: 2010
Keywords
initial algebras, fibrational induction, polynomial

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