77 research outputs found
Applying Formal Methods to Networking: Theory, Techniques and Applications
Despite its great importance, modern network infrastructure is remarkable for
the lack of rigor in its engineering. The Internet which began as a research
experiment was never designed to handle the users and applications it hosts
today. The lack of formalization of the Internet architecture meant limited
abstractions and modularity, especially for the control and management planes,
thus requiring for every new need a new protocol built from scratch. This led
to an unwieldy ossified Internet architecture resistant to any attempts at
formal verification, and an Internet culture where expediency and pragmatism
are favored over formal correctness. Fortunately, recent work in the space of
clean slate Internet design---especially, the software defined networking (SDN)
paradigm---offers the Internet community another chance to develop the right
kind of architecture and abstractions. This has also led to a great resurgence
in interest of applying formal methods to specification, verification, and
synthesis of networking protocols and applications. In this paper, we present a
self-contained tutorial of the formidable amount of work that has been done in
formal methods, and present a survey of its applications to networking.Comment: 30 pages, submitted to IEEE Communications Surveys and Tutorial
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Tactics From Proofs
Proof guarantees the correctness of a formal specification with respect to formal requirements, and of an implementation with respect to a specification, and so provides valuable verification methods in high integrity system development. However, proof development by hand tends to be an erudite, error-prone and seemingly interminable task.
Tactics are programs that drive theorem-provers, thus automating proof development and alleviating some of the problems mentioned above. The development of tactics for a particular application domain also extends the domain of application of the theorem-prover. A LCF-tactic is safe in that if it fails to be applicable to a particular conjecture, then it will not produce an incorrect proof.
The current construction of tactics from proofs does not yield sufficiently robust tactics. Proofs tend to be specific to the details of a specification and so are not reusable in general, e.g. the same proof may not work when the definition of a conjecture is changed. The major challenges in proof development are deciding which proof rule and instantiations to apply in order to prove a conjecture.
Discerning patterns in formal interactive proof development facilitates the construction of robust tactics that can withstand definitional changes in conjectures. Having developed an interactive proof for a conjecture, we develop the necessary abstractions of the proof steps used, to construct a tactic th at can be applicable to other conjectures in that domain. By so doing we encode human expertise used in the proof development, and make proofs robust and thus generally reusable.
We apply our theory on the proofs of conjectures involving some set theory operators, and on the proof obligations that arise in the formal development of numerical specifications using the retrenchment method under the IEEE-854 floating-point standard in the PVS theorem-prover/proof-checker
Introduction to the Literature on Semantics
An introduction to the literature on semantics. Included are pointers to the literature on axiomatic semantics, denotational semantics, operational semantics, and type theory
Twee: An Equational Theorem Prover
Twee is an automated theorem prover for equational logic. It implements unfailing Knuth-Bendix completion with ground joinability testing and a connectedness-based redundancy criterion. It came second in the UEQ division of CASC-J10, solving some problems that no other system solved. This paper describes Twee’s design and implementation
Synchronous Digital Circuits as Functional Programs
Functional programming techniques have been used to describe synchronous digital circuits since the early 1980s and have proven successful at describing certain types of designs. Here we survey the systems and formal underpinnings that constitute this tradition. We situate these techniques with respect to other formal methods for hardware design and discuss the work yet to be done
CPO Models for GSOS Languages - Part I: Compact GSOS Languages
In this paper, we present a general way of giving denotational semantics to a class of languages equipped with an operational semantics that fits the GSOS format of Bloom, Istrail and Meyer. The canonical model used for this purpose will be Abramsky's domain of synchronization trees, and the denotational semantics automatically generated by our methods will be guaranteed to be fully abstract with respect to the finitely observable part of the bisimulation preorder. In the process of establishing the full abstraction result, we also obtain several general results on the bisimulation preorder (including a complete axiomatization for it), and give a novel operational interpretation of GSOS languages
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