An incremental prototyping methodology for distributed systems based on formal specifications

This thesis presents a new incremental prototyping methodology for formally specified distributed systems. The objective of this methodology is to fill the gap which currently exists between the phase where a specification is simulated, generally using some sequential logical inference tool, and the phase where the modeled system has a reliable, efficient and maintainable distributed implementation in a main-stream object-oriented programming language. This objective is realized by application of a methodology we call Mixed Prototyping with Object-Orientation (in short: OOMP). This is an extension of an existing approach, namely Mixed Prototyping, that we have adapted to the object-oriented paradigm, of which we exploit the flexibility and inherent capability of modeling abstract entities. The OOMP process proceeds as follows. First, the source specifications are automatically translated into a class-based object-oriented language, thus providing a portable and high-level initial implementation. The generated class hierarchy is designed so that the developer may independently derive new sub-classes in order to make the prototype more efficient or to add functionalities that could not be specified with the given formalism. This prototyping process is performed incrementally in order to safely validate the modifications against the semantics of the specification. The resulting prototype can finally be considered as the end-user implementation of the specified software. The originality of our approach is that we exploit object-oriented programming techniques in the implementation of formal specifications in order to gain flexibility in the development process. Simultaneously, the object paradigm gives the means to harness this newly acquired freedom by allowing automatic generation of test routines which verify the conformance of the hand-written code with respect to the specifications. We demonstrate the generality of our prototyping scheme by applying it to a distributed collaborative diary program within the frame of CO-OPN (Concurrent Object-Oriented Petri Nets), a very powerful specification formalism which allows expressing concurrent and non-deterministic behaviours, and which provides structuring facilities such as modularity, encapsulation and genericity. An important effort has also been accomplished in the development or adaptation of distributed algorithms for cooperative symbolic resolution. These algorithms are used in the run-time support of the generated CO-OPN prototypes

Flexible and Efficient Measurement of Dynamic Bytecode Metrics

Code instrumentation is finding more and more practical applications, but the required program transformations are often difficult to implement, due to the lack of dedicated, high-level tools. In this paper we present a novel instrumentation framework that supports the partial evaluation of compiled Java code transformation templates, with the goal of efficiently measuring chosen dynamic bytecode and control flow metrics. This framework, as well as the instrumentation code it generates, is implemented in pure Java and hence completely platform-independent. We show the benefits of our approach in several application areas, such as platform-independent resource management and profiling of software components

Program Transformations for Light-Weight CPU Accounting and Control in the Java Virtual Machine - A Systematic Review

This article constitutes a thorough presentation of an original scheme for portable CPU accounting and control in Java, which is based on program transformation techniques at the bytecode level and can be used with every standard Java Virtual Machine. In our approach applications, middleware, and even the standard Java runtime libraries (i.e., the Java Development Kit) are modified in a fully portable way, in order to expose details regarding the execution of threads. These transformations however incur a certain overhead at runtime. Further contributions of this article are the systematic review of the origin of such overheads and the description of a new static path prediction scheme targeted at reducing them

Monitoring of Resource Consumption in Java-based Application Servers

To realize dependable and profitable information and communication systems, computing resources (CPU, memory, network bandwidth) should be taken into account to a much wider extent than they are today. E-commerce infrastructure, such as application servers, are especially concerned by this issue. This paper shows how an existing Java-based code transformation framework was extended to enable transparent monitoring of resource consumption within the open source Apache Tomcat servlet engine

A Quantitative Evaluation of the Contribution of Native Code to Java Workloads

Many performance analysis tools for Java focus on tracking executed bytecodes, but provide little support in determining the specific contribution of native code libraries. This paper introduces and assesses a portable approach for characterizing the amount of native code executed by Java applications. A profiling agent based on the JVM Tool Interface (JVMTI) accurately keeps track of all runtime transitions between bytecode and native code. It relies on a combination of JVMTI events, Java Native Interface (JNI) function interception, bytecode instrumentation, and hardware performance counters

Platform-independent profiling in a virtual execution environment

Virtual execution environments, such as the Java virtual machine, promote platform-independent software development. However, when it comes to analyzing algorithm complexity and performance bottlenecks, available tools focus on platform-specific metrics, such as the CPU time consumption on a particular system. Other drawbacks of many prevailing profiling tools are high overhead, significant measurement perturbation, as well as reduced portability of profiling tools, which are often implemented in platform-dependent native code. This article presents a novel profiling approach, which is entirely based on program transformation techniques, in order to build a profiling data structure that provides calling-context-sensitive program execution statistics. We explore the use of platform-independent profiling metrics in order to make the instrumentation entirely portable and to generate reproducible profiles. We implemented these ideas within a Java-based profiling tool called JP. A significant novelty is that this tool achieves complete bytecode coverage by statically instrumenting the core runtime libraries and dynamically instrumenting the rest of the code. JP provides a small and flexible API to write customized profiling agents in pure Java, which are periodically activated to process the collected profiling information. Performance measurements point out that, despite the presence of dynamic instrumentation, JP causes significantly less overhead than a prevailing tool for the profiling of Java code

Conception collaborative du jeu Péroll'ard ::outils, méthodes et processus

La création de dispositifs à visée éducative et ludique est un processus complexe qui rend nécessaire l’adoption d’une ingénierie spécifique et collaborative. Cet article a pour objectif de décrire les outils, méthodes et processus mis en place lors de la conception d’un jeu permettant la découverte de l’Université de Fribourg. Sur la base de méthodes agiles et centrées utilisateurs, un groupe de chercheurs, experts pédagogiques et informaticiens collaborent à la réalisation de dispositifs pédagogiques et à l’intégration de mécaniques de jeux. L’analyse de l’ensemble du processus permet, par itération, d’adapter et d’affiner les méthodologies de conception de ressources ludo-pédagogiques

Frugal Mobile Objects

This paper presents a computing model for resource-limited mobile devices. The originality of the model lies in the integration of a strongly-typed event-based communication paradigm with abstractions for frugal control, assuming a small footprint runtime. With our model, an application consists of a set of distributed reactive objects, called FROBs, that communicate through typed events and dynamically adapt their behavior reacting to notifications typically based on resource availability. FROBs have a logical time-slicing execution pattern that helps monitor resource consuming tasks and determine resource profiles in terms of CPU, memory, and bandwidth. The behavior of a FROB is represented by a set of stateless first-class objects. Both state and behavioral objects are referenced through a level of indirection within the FROB. This facilitates the dynamic changes of the set of event types a FROB can accept, say based on the available resources, without requiring a significant footprint of the underlying FROB runtime. We demonstrate the usability of the FROB model through our Java-based prototype and a peer-to-peer audio streaming scenario where an audio provider dynamically adjusts its quality of service by adapting to demand. The performance results of our prototype convey the small footprint of our FROB runtime (86 kilobytes). We also augmented the KVM to enable resource profiling with however a negligible overhead (less than 0.5%) and a decrease in speed of the virtual machine of at most 7%

An Evolutive Distributed Algebraic Petri Nets Simulator

This paper presents a new prototyping methodology for large concurrent systems modelled by the means of hierarchical algebraic Petri nets. First, the source specifications are automatically translated into a main-stream object-oriented language, thus providing a portable and high-level initial implementation. The generated class hierarchy is designed so that the developer may then independantly derive new sub-classes in order to make the simulator more efficient or to add functionalities that could not be specified with Petri nets. This prototyping process is performed incrementally in order to safely validate the modifications against the semantics of the specification. The resulting simulator can finally be considered as the end-user implementation of the specified software system. The originality of our scheme is that we exploit object-oriented programming techniques in the implementation of formal specifications in order to gain flexibility in the development process, and simultaneously to harness this newly acquired freedom