Marc Pantel

A set-constraint-based analysis of actors

This paper presents a type inference system for a primitive actor calculus (Cap) based on set-constraints resolution. In contrast with concurrent objects, actors can change dynamically their interface (the set of messages they can handle). Therefore, the Cap calculus reduction rules can lead to orphan messages which will never be handled. The aim of the inference system is to detect statically many orphan messages and to produce information leading to the dynamic detection of the others. In this purpose, we define a flattening operation which abstracts the various behaviors of an actor. This static analysis is based on Aiken and Wimmers set-constraints resolution. It gives slightly better results than Vasconcelos or Yonezawa kinded types based analysis for concurrent objects.

From Design to Implementation: An Automated, Credible Autocoding Chain for Control Systems

In a context of heightened safety requirements for safety-critical embedded systems and ever-increasing costs of verification and validation, we describe a fully automated, credible autocoding chain for control systems. This chain generates code, along with guarantees of high level functional properties, which cans be independently verified. The platform relies on domain specific knowledge and formal analysis methods to bridge the semantic gap between domain experts and code verification experts. First, a graphical dataflow language is extended with annotation symbols, enabling the control engineer to express high level properties of its control law within the framework of a familiar block-diagram language. A public-domain autocoder is enhanced not only to generate the code implementing the initial design, but also to carry high level properties down to annotations at the level of the code. Finally, using customized code analysis tools, certificates are generated, which guarantee the correctness of the annotations with respect to the code, and can be verified using existing static analysis tools. For now, we limit the conclusions to the bounded-input bounded-output characteristic of linear controllers, however the approach appears readily extendable to a broader array of properties and systems.

Static safety analysis for non-uniform service availability in Actors

The main purpose of this work is the static detection of orphan messages in actor based languages. An orphan is a message which may not be handled by its target in some execution paths. Two kinds of orphan messages may be encountered, i.e., safety and liveness ones. Safety orphans occur when all target behaviors on a given execution path do not know how to handle the message. Liveness orphans occur when one of the target behaviors in each execution path knows how to handle the message but the target is deadlocked and will never assume the corresponding behavior. This paper presents a safe static analysis which detects all safety orphan messages in actor-based programs. This result extends previous work derived from sequential object-oriented languages type systems to non-uniform behaviors.

Towards an incremental development of discrete-event simulators for batch plants: Use of object-oriented concepts

Abstract This paper deals with the development of a general methodology for designing discrete-event simulators (DES) for batch plants, using object-oriented techniques. This approach was first applied to the design of a DES model for a semiconductor facility (MELISSA) and to the extension to a fine chemistry environment (AD-HOC). It is shown that the use of an object-oriented language led to a great reduction in the rewriting cost from MELISSA to AD-HOC.

Advanced service trading for scientific computing over the grid

One of the great benefits of computational grids is to give access to a wide range of scientific software and computers with different architectures. It is then possible to use a huge variety of tools for solving the same problem and even to combine these tools in order to obtain the best solution.Grid service trading (searching for the best combination of software and execution platform according to the user requirements) is thus a crucial issue. Trading relies on the description of available services and computers, on the current state of the grid, and on the user requirements. Given the large amount of services that may be deployed over the grid, this description cannot be reduced to a simple service name.A sophisticated service specification approach similar to algebraic data type is presented in this paper. Services are described in terms of their algebraic and semantic properties. This is nothing else than proceeding to a description of algorithms and objects properties for a given application domain.We then illustrate how this specification can be used to determine the service or the combination of services that best answer a user request. As a major benefit, users are not required to explicitly call grid-services, but instead manipulate high-level domain-specific expressions.Our approach is fully generic and can be used in almost all application domains. We illustrate this approach and its possible limitations within the framework of dense linear algebra. More precisely, we focus on Level 3 BLAS (ACM Trans Math Softw 16:1–17, 1990; ibid 16:18–28, 1990) and LAPACK (Society for Industrial and Applied Mathematics, Philadelphia, 1999). Some examples in nonlinear optimization are also given to demonstrate how generic our approach is and report on experiments where both domains interact to show the multi-domain possibilities.

Mathematical Service Trading Based on Equational Matching

Mathematical software libraries provide many computational services. Mathematical operators properties can be used to combine several services in order to provide more complex ones or to adapt a given service to a slightly different use. The computational grid provides users with access to most of the available software libraries. Service trading, that is searching for services able to fulfil a user requirements is therefore difficult as many different services and service combinations from different libraries can fulfil the same requirements. Usual proposals rely on the use of the service interface and/or domain specific meta-data and ontologies. The service semantics defined in these framework are either easy to use but too poor or application dependent (interface and meta-data); or too complex and sophisticated (ontologies logic) for the common user. The purpose of our work is to provide a trading framework which is both easy to use for specialist of application domains and precise enough to allow service adaptation and combination during the trading process. Our proposal is based on algebraic specification (related to OpenMath) for domain and service description and equational matching for service trading, adaptation and combination. This paper presents our framework proposal and the associated trading algorithm which is both sound and complete: it can find all the appropriate services and combinations according to the given semantics.

Development of flexible peer-to-peer information systems using adaptable mobile agents

Wide-area networks provide an easy access to many different distributed and heterogeneous data sources. The development of automated operating tools is still complex, particularly because of evolution and adaptation requirements (to the data sources structures and to the network quality of service). The purpose of this paper is to evaluate the advantages of adaptable mobile agents in order to simplify the development and the deployment. As an experiment, we develop a prototype of peer-to-peer information system, and we show how agent mobility and adaptation abilities help in implementing various forms of adaptation: adaptation to the execution context, access to new servers with initially unknown communication protocols, dynamic modification of search algorithms based on results provided by the servers. Then, we show how these techniques can be easily extended to other problems such as search and upgrade of software components.

Semantic-based service trading: application to linear algebra

One of the great benefit of computational grids is to provide access to a wide range of scientific software and computers with different architectures. It is then possible to use a variety of tools for solving the same problem and even to combine these tools in order to obtain the best solution technique. n nGrid service trading (searching for the best combination of software and execution platform according to the user requirements) is thus a crucial issue. Trading relies both on the description of available services and computers, on the current state of the grid, and on the user requirements. Given the large amount of services available on the Grid, this description cannot be reduced to a simple service name. n nWe present in this paper a more sophisticated service description similar to algebraic data type. We then illustrate how it can be used to determine the combinations of services that answer a user request. As a side effect, users do not make direct explicit calls to grid-services but talk to a more applicative-domain specific service trader. n nWe illustrate this approach and its possible limitations within the framework of dense linear algebra. More precisely we focus on Level 3 BLAS ([DDDH90a, DDDH90b]) and LAPACK ([ABB+99]) type of basic operations.

Management of services based on a semantic description within the GRID-TLSE project

The goal of the GRID-TLSE Project is to design an expert site that provides an easy access to a number of tools allowing comparative analysis of sparse matrix packages on a user-submitted problem, as well as on particular matrices from the matrix collection also available on the site. n nWhen making available a large amount of software over a computational Grid, facilitating its deployment and its exploitation become crucial. Within the GRID-TLSE Project, we use a software component approach based on a high level semantic description of the scientific computing services. In this paper, we focus on one aspect of this description of the computational services: the use of meta-data called abstract parameters. Our approach allows the automatic discovery and the exploitation of new services throught the concept of scenario.

Temporal Logic Based Static Analysis for Non-uniform Behaviours

The main purpose of our work is the typing of concurrent, distributed and mobile programs based on the actor programming model, that is non-uniform behaviour concurrent objects communicating by asynchronous message passing. One of the key difficulties is to give a precise definition of ”message not understood” errors in this context. In this paper, we investigate temporal logic and model-checking based technologies for an asynchronous message passing process calculi. We focus on non uniform input interfaces for processes, and then define a temporal logic tailored to their description and analyses. This logic deals with infinite-state systems, as mailboxes of actors are unbounded multisets of messages, but yet happens to be decidable. We use our logic to specify possible communication errors in actor-based programs in order to give precise and sound definition of type disciplines.