University of Birmingham > Talks@bham > Theoretical computer science seminar > Realizability in Cyclic Proof: Extracting Ordering Information for Infinite Descent

## Realizability in Cyclic Proof: Extracting Ordering Information for Infinite DescentAdd to your list(s) Download to your calendar using vCal - Reuben Rowe (University of Kent at Canterbury)
- Friday 06 October 2017, 11:00-12:00
- Computer Science, The Sloman Lounge (UG).
If you have a question about this talk, please contact Paul Taylor. In program verification, measures for proving the termination of programs are typically constructed using (notions of size for) the data manipulated by the program. Such data are often described by means of logical formulas. For example, the cyclic proof technique makes use of semantic approximations of inductively defined predicates to construct Fermat-style infinite descent arguments. However, logical formulas must often incorporate explicit size information (e.g. a list length parameter) in order to support inter-procedural analysis. In this paper, we show that information relating the sizes of inductively defined data can be automatically extracted from cyclic proofs of logical entailments. We characterise this information in terms of a graph-theoretic condition on proofs, and show that this condition can be encoded as a containment between weighted automata. We also show that under certain conditions this containment falls within known decidability results. Our results can be viewed as a form of realizability for cyclic proof theory. This talk is part of the Theoretical computer science seminar series. ## This talk is included in these lists:- Computer Science Departmental Series
- Computer Science Distinguished Seminars
- Computer Science, The Sloman Lounge (UG)
- Theoretical computer science seminar
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