Conditions, constraints and contracts: on the use of annotations for policy modeling.

Organisational policies express constraints on generation and processing of resources. However, application domains rely on transformation processes, which are in principle orthogonal to policy specifications and domain rules and policies may evolve in a non-synchronised way. In previous papers, we have proposed annotations as a flexible way to model aspects of some policy, and showed how they could be used to impose constraints on domain configurations, how to derive application conditions on transformations, and how to annotate complex patterns. We extend the approach by: allowing domain model elements to be annotated with collections of elements, which can be collectively applied to individual resources or collections thereof; proposing an original construction to solve the problem of annotations remaining orphan , when annotated resources are consumed; introducing a notion of contract, by which a policy imposes additional pre-conditions and post-conditions on rules for deriving new resources. We discuss a concrete case study of linguistic resources, annotated with information on the licenses under which they can be used. The annotation framework allows forms of reasoning such as identifying conflicts among licenses, enforcing the presence of licenses, or ruling out some modifications of a licence configuration

A framework for deadlock detection in core ABS

We present a framework for statically detecting deadlocks in a concurrent object-oriented language with asynchronous method calls and cooperative scheduling of method activations. Since this language features recursion and dynamic resource creation, deadlock detection is extremely complex and state-of-the-art solutions either give imprecise answers or do not scale. In order to augment precision and scalability we propose a modular framework that allows several techniques to be combined. The basic component of the framework is a front-end inference algorithm that extracts abstract behavioural descriptions of methods, called contracts, which retain resource dependency information. This component is integrated with a number of possible different back-ends that analyse contracts and derive deadlock information. As a proof-of-concept, we discuss two such back-ends: (i) an evaluator that computes a fixpoint semantics and (ii) an evaluator using abstract model checking.Comment: Software and Systems Modeling, Springer Verlag, 201

On the Realization of TractsTool

Model transformations play an important role in Model-Driven Engineering (MDE), and as their size and complexity grow, there is an increasing need to count on tool support for testing their correctness. In this presentation, we introduce TractsTool, a tool for specifying and testing several different kinds of model transformations, e.g., model-to-model, model-to-text, and text-to-model transformations, based on contracts. We explain the main principles behind the tool, demonstrate some of its capabilities by a running example, and show how it is internally realized by using MDE techniques. In particular, we describe the transformation chain that is used to compute the test results. TractsTool with accompanying information is available at: http://atenea.lcc.uma.es/index.php/Main_Page/Resources/Tract

On conservativity of concurrent Haskell

The calculus CHF models Concurrent Haskell extended by concurrent, implicit futures. It is a process calculus with concurrent threads, monadic concurrent evaluation, and includes a pure functional lambda-calculus which comprises data constructors, case-expressions, letrec-expressions, and Haskell’s seq. Futures can be implemented in Concurrent Haskell using the primitive unsafeInterleaveIO, which is available in most implementations of Haskell. Our main result is conservativity of CHF, that is, all equivalences of pure functional expressions are also valid in CHF. This implies that compiler optimizations and transformations from pure Haskell remain valid in Concurrent Haskell even if it is extended by futures. We also show that this is no longer valid if Concurrent Haskell is extended by the arbitrary use of unsafeInterleaveIO

Legendre's Relation and the Quantum Equivalence osp(4|4)_(1) = osp(2|2)_(-2) + su(2)_(0)

Using explicit results for the four-point correlation functions of the Wess-Zumino-Novikov-Witten (WZNW) model we discuss the conformal embedding osp(4|4)_(1) = osp(2|2)_(-2) + su(2)_(0). This embedding has emerged in Bernard and LeClair's recent paper [1]. Given that the osp(4|4)_(1) WZNW model is a free theory with power law correlation functions, whereas the su(2)_(0) and osp(2|2)_(-2) models are CFTs with logarithmic correlation functions, one immediately wonders whether or not it is possible to combine these logarithms and obtain simple power laws. Indeed, this very concern has been raised in a revised version of [1]. In this paper we demonstrate how one may recover the free field behaviour from a braiding of the solutions of the su(2)_(0) and osp(2|2)_(-2) Knizhnik-Zamolodchikov equations. We do this by implementing a procedure analogous to the conformal bootstrap programme [2]. Our ability to recover such simple behaviour relies on a remarkable identity in the theory of elliptic integrals known as Legendre's relation.Comment: 13 pages, RevTe