Functional programs: conversions between deep and shallow embeddings

Abstract. This paper presents a method which simplifies verification of deeply embedded functional programs. We present a technique by which proof-certified equations describing the effect of functional programs (shallow embeddings) can be automatically extracted from their operational semantics. Our method can be used in reverse, i.e. from shallow to deep embeddings, and thus for implementing certifying code synthesis: we have implemented a tool which maps HOL functions to equivalent Lisp functions, for which we have a verified Lisp runtime. A key benefit, in both directions, is that the verifier does not need to understand the operational semantics that gives meanings to the deep embeddings.

A trustworthy monadic formalization of the armv7 instruction set architecture

Abstract. This paper presents a new HOL4 formalization of the current ARM instruction set architecture, ARMv7. This is a modern RISC architecture with many advanced features. The formalization is detailed and extensive. Considerable tool support has been developed, with the goal of making the model accessible and easy to work with. The model and supporting tools are publicly available – we wish to encourage others to make use of this resource. This paper explains our monadic specification approach and gives some details of the endeavours that have been made to ensure that the sizeable model is valid and trustworthy. A novel and efficient testing approach has been developed, based on automated forward proof and communication with ARM development boards.

Post-traumatic mutism in children: clinical characteristics, pattern of recovery and clinicopathological correlations.

Among the numerous clinical syndromes observed after severe traumatic head injury, post-traumatic mutism is a disorder rarely reported in adults and not studied in any detail in children. We report seven children between the ages of 3 1/2 and 14 years who sustained severe head injury and developed post-traumatic mutism. We aim to give a precise clinical characterization of this disorder, discuss differential diagnosis and correlations with brain imaging and suggest its probable neurological substrate. After a coma lasting from 5 to 25 days, the seven patients who suffered from post-traumatic mutism went through a period of total absence of verbal production lasting from 5 to 94 days, associated with the recovery of non-verbal communication skills and emotional vocalization. During the first days after the recovery of speech, all patients were able to produce correct small sentences with a hypophonic and monotonous voice, moderate dysarthria, word finding difficulties but no signs of aphasia, and preserved oral comprehension. The neurological signs in the acute phase (III nerve paresis in three of seven patients, signs of autonomic dysfunctions in five of seven patients), the results of the brain imaging and the experimental animal data all suggest the involvement of mesencephalic structures as playing a key role in the aetiology of post-traumatic mutism

An automata-theoretic approach to reasoning about infinite-state systems

Abstract. We develop an automata-theoretic framework for reasoning about infinitestate sequential systems. Our framework is based on the observation that states of such systems, which carry a finite but unbounded amount of information, can be viewed as nodes in an infinite tree, and transitions between states can be simulated by finite-state automata. Checking that the system satisfies a temporal property can then be done by an alternating two-way tree automaton that navigates through the tree. As has been the case with finite-state systems, the automatatheoretic framework is quite versatile. We demonstrate it by solving several versions of the model-checking problem for §-calculus specifications and prefixrecognizable systems, and by solving the realizability and synthesis problems for §-calculus specifications with respect to prefix-recognizable environments.