Mechanized semantics

The goal of this lecture is to show how modern theorem provers---in this case, the Coq proof assistant---can be used to mechanize the specification of programming languages and their semantics, and to reason over individual programs and over generic program transformations, as typically found in compilers. The topics covered include: operational semantics (small-step, big-step, definitional interpreters); a simple form of denotational semantics; axiomatic semantics and Hoare logic; generation of verification conditions, with application to program proof; compilation to virtual machine code and its proof of correctness; an example of an optimizing program transformation (dead code elimination) and its proof of correctness

Fusing Logic And Control With Local Transformations: An Example Optimization

Programming supports the separation of logical concerns from issues of control in program construction. While this separation of concerns leads to reduced code size and increased reusability of code, its main disadvantage is the computational overhead it incurs. Fusion techniques can be used to combine the reusability of abstract programs with the efficiency of specialized programs. In this paper we illustrate some of the ways in which rewriting strategies can be used to separate the definition of program transformation rules from the strategies under which they are applied. Doing so supports the generic definition of program transformation components. Fusion techniques for strategies can then be used to specialize such generic components. We show how the generic innermost rewriting strategy can be optimized by fusing it with the rules to which it is applied. Both the optimization and the programs to which the optimization applies are specified in the strategy language Stratego. The optimization is based on small transformation rules that are applied locally under the control of strategies, using special knowledge about the contexts in which the rules are applied

High-precision calculation of multi-loop Feynman integrals by difference equations

We describe a new method of calculation of generic multi-loop master integrals based on the numerical solution of systems of difference equations in one variable. We show algorithms for the construction of the systems using integration-by-parts identities and methods of solutions by means of expansions in factorial series and Laplace's transformation. We also describe new algorithms for the identification of master integrals and the reduction of generic Feynman integrals to master integrals, and procedures for generating and solving systems of differential equations in masses and momenta for master integrals. We apply our method to the calculation of the master integrals of massive vacuum and self-energy diagrams up to three loops and of massive vertex and box diagrams up to two loops. Implementation in a computer program of our approach is described. Important features of the implementation are: the ability to deal with hundreds of master integrals and the ability to obtain very high precision results expanded at will in the number of dimensions.Comment: 55 pages, 5 figures, LaTe

Solving the TTC 2011 Reengineering Case with MOLA and Higher-Order Transformations

The Reengineering Case of the Transformation Tool Contest 2011 deals with automatic extraction of state machine from Java source code. The transformation task involves complex, non-local matching of model elements. This paper contains the solution of the task using model transformation language MOLA. The MOLA solution uses higher-order transformations (HOT-s) to generate a part of the required MOLA program. The described HOT approach allows creating reusable, complex model transformation libraries for generic tasks without modifying an implementation of a model transformation language. Thus model transformation users who are not the developers of the language can achieve the desired functionality more easily.Comment: In Proceedings TTC 2011, arXiv:1111.440

The suitability of MSP for engineering infrastructure

This paper arose from empirical investigations of practitioner views of both governance and program definitions together with investigations of practitioner reference documents. These investigations indicated that some confusion had arisen in infrastructure project management as a result of approaches used in IT. This paper contributes to the literature evaluating project standards and methodologies by conducting an examination of the suitability of one such source (MSP) for use in engineering infrastructure program management. A deductive definitional approach is taken to identify features that could cause difficulty. Eight features were examined, and six were found to have difficulty in application to engineering infrastructure. The remaining two were found to be terminology differences that are unlikely to cause too much difficulty. The features causing difficulty include an inappropriate definition of a program, use of a non-generic process flow unsuitable for rolling programs, confusion of transformation projects with programs, the presumption of a board governance model, and confusion of large projects with programs. The paper concludes that MSP is quite poorly suited to managing rolling programs, whether they are in engineering infrastructure or IT. Various changes to MSP and PMI publications are recommended