# Computer-Aided Formal Verification: 2020-2021

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| Schedule S1(CS&P) — Computer Science and Philosophy Schedule S1 — Computer Science Schedule S1(M&CS) — Mathematics and Computer Science |

| Michaelmas Term 2020 (16 lectures) |

## Overview

This course introduces the fundamentals of computer-aided formal verification. Computer-aided formal verification aims to improve the quality of digital systems by using logical reasoning, supported by automated software tools, to analyse their designs. The idea is to build a mathematical model of a system and then try to prove formal properties of it that validate the system's correctness, or at least that help discover subtle bugs. The proofs can be millions of lines long, so specially-designed computer algorithms are used to search for and check them. Properties are formalised as formulae in proper temporal logics.This course provides a survey of several major software-assisted verification methods, covering both theory and practical applications. The aim is to familiarise students with the mathematical principles behind current verification technologies, and provide them with an appreciation of how these technologies are used in industrial system design today.

## Synopsis

- Introduction to CAFV
- Modelling sequential systems as labelled transition systems (Kripke structures)
- Linear time properties
- Linear temporal logic (LTL)
- Computation tree logic (CTL) and CTL*
- Counterexamples and witnesses
- Model checking CTL
- Model checking LTL
- Binary decision diagrams (BDD)
- Symbolic model checking
- Model checking with SAT, bounded model checking
- Completeness thresholds and k-induction
- Craig interpolation
- Equivalences and abstractions
- Decision procedures in model checking
- Practical, industrial-scale verification; present challenges

## Syllabus

Introduction to computer-aided formal verification. Modelling sequential systems as labelled transition systems (Kripke structures). Linear time properties. Linear temporal logic (LTL). Computation tree logic (CTL) and CTL*. Model checking CTL. Model checking LTL. Counterexamples and witnesses. Binary decision diagrams (BDD). Symbolic model checking. Model checking with SAT, bounded model checking. Completeness thresholds and k-induction. Craig interpolation. Equivalences and abstractions. Decision procedures in model checking. Practical, industrial-scale verification; present challenges

## Reading list

The lectures will be supplemented with notes and pointers to published articles in the field. The following may be helpful for reference or further reading on specific topics.

**Surveys**

*Formal Verification in Hardware Design: A Survey*, by C. Kern and M. R. Greenstreet, ACM Transactions on Design Automation of Systems, v. 4, pp. 123-193, 2009-
*A Survey of Automated Techniques for Formal Software Verification*, by D'Silva et al.,*IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems*, v. 27(7), pp. 1165-1178, 2008

**Temporal Logics**

*From Philosophical to Industrial Logics*, by M. Vardi, ICLA 2009

**Binary Decision Diagrams and SAT**

- An Introduction to Binary Decision Diagrams, by Henrik Reif Andersen, Lecture Notes (Technical University of Denmark, October 1997)
*Formal Hardware Verification with BDDs: An Introduction*, by Alan J. Hu, IEEE Pacific Rim Conference on Communications, Computers, and Signal Processing, pp. 677-682, 1997*Decision Procedures*, by Daniel Kroening and Ofer Strichman (Springer Verlag, 2008)

**Model Checking**

- Logic in Computer Science: Modelling and reasoning about systems, by Michael Huth and Mark Ryan (Cambridge University Press, 2000)
- Model Checking, by Edmund M. Clarke, Jr., Orna Grumberg, and Doron A. Peled, Second edition (The MIT Press, 2000)
*Principles of Model Checking*, by C. Baier and J.-P. Katoen (The MIT Press, 2008)

## Related research

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| Model Checking | Concurrency | Software Model Checking | Hardware Verification | Quantitative Analysis and Verification | Verification |