On Modelling and Analysis of Dynamic Reconfiguration of Dependable Real-Time Systems

This paper motivates the need for a formalism for the modelling and analysis of dynamic reconfiguration of dependable real-time systems. We present requirements that the formalism must meet, and use these to evaluate well established formalisms and two process algebras that we have been developing, namely, Webpi and CCSdp. A simple case study is developed to illustrate the modelling power of these two formalisms. The paper shows how Webpi and CCSdp represent a significant step forward in modelling adaptive and dependable real-time systems.Comment: Presented and published at DEPEND 201

Formal Power Analysis of Systems-on-Chip

The design methods and languages targeted to modern System-on-Chip designs are facing tremendous pressure of the ever-increasing complexity, power, and speed requirements. To estimate any of these three metrics, there is a trade-off between accuracy and abstraction level of detail in which a system under design is analyzed. The more detailed the description, the more accurate the simulation will be, but, on the other hand, the more time consuming it will be. Moreover, a designer wants to make decisions as early as possible in the design flow to avoid costly design backtracking. To answer the challenges posed upon System-on-chip designs, this thesis introduces a formal, power aware framework, its development methods, and methods to constraint and analyze power consumption of the system under design. This thesis discusses on power analysis of synchronous and asynchronous systems not forgetting the communication aspects of these systems. The presented framework is built upon the Timed Action System formalism, which offer an environment to analyze and constraint the functional and temporal behavior of the system at high abstraction level. Furthermore, due to the complexity of System-on-Chip designs, the possibility to abstract unnecessary implementation details at higher abstraction levels is an essential part of the introduced design framework. With the encapsulation and abstraction techniques incorporated with the procedure based communication allows a designer to use the presented power aware framework in modeling these large scale systems. The introduced techniques also enable one to subdivide the development of communication and computation into own tasks. This property is taken into account in the power analysis part as well. Furthermore, the presented framework is developed in a way that it can be used throughout the design project. In other words, a designer is able to model and analyze systems from an abstract specification down to an implementable specification.Siirretty Doriast

09091 Abstracts Collection -- Formal Methods in Molecular Biology

From 23. February to 27. February 2009, the Dagstuhl Seminar 09091 ``Formal Methods in Molecular Biology \u27\u27 was held in Schloss Dagstuhl~--~Leibniz Center for Informatics. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

Orchestrating Tuple-based Languages

The World Wide Web can be thought of as a global computing architecture supporting the deployment of distributed networked applications. Currently, such applications can be programmed by resorting mainly to two distinct paradigms: one devised for orchestrating distributed services, and the other designed for coordinating distributed (possibly mobile) agents. In this paper, the issue of designing a pro- gramming language aiming at reconciling orchestration and coordination is investigated. Taking as starting point the orchestration calculus Orc and the tuple-based coordination language Klaim, a new formalism is introduced combining concepts and primitives of the original calculi. To demonstrate feasibility and effectiveness of the proposed approach, a prototype implementation of the new formalism is described and it is then used to tackle a case study dealing with a simplified but realistic electronic marketplace, where a number of on-line stores allow client applications to access information about their goods and to place orders

Behavioral types in programming languages

A recent trend in programming language research is to use behav- ioral type theory to ensure various correctness properties of large- scale, communication-intensive systems. Behavioral types encompass concepts such as interfaces, communication protocols, contracts, and choreography. The successful application of behavioral types requires a solid understanding of several practical aspects, from their represen- tation in a concrete programming language, to their integration with other programming constructs such as methods and functions, to de- sign and monitoring methodologies that take behaviors into account. This survey provides an overview of the state of the art of these aspects, which we summarize as the pragmatics of behavioral types

Real and stochastic time in process algebras for performance evaluation

Process algebras are formalisms for abstract modeling of systems for the purpose of qualitative veri¯cation and quantitative evaluation. The purpose of veri¯cation is to show that the system behaves correctly, e.g., it does not contain a deadlock or a state with some desired property is eventually going to be reached. The quantitative or performance evaluation part gives an approximation how well the system will behave, e.g., the average time of a message to get through is 10 time units or the utilization (percentage of time that something is used) of some machine is 23.5 percent. Originally, process algebras were only developed for qualitative model- ing, but gradually they have been extended with time, probabilities, and Markovian (exponential) and generally-distributed stochastic time. The ex- tensions up to stochastic time typically conservatively extended previous well-established theories. However, mostly due to the nature of the under- lying (non-)Markovian performance models, the stochastic process algebras were built from scratch. These extensions were carried out as orthogonal extensions of untimed process theories with exponential delays or stochastic clocks. The underlying performance model is obtained by abstracting from the qualitative behavior using some weak behavioral equivalence. The thesis investigates several issues: (1) What is the relationship be- tween discrete real and generally-distributed stochastic time in the process theories? (2) Is it possible, and if so, how, to extend timed process theories with stochastic time? (3) Reversely, is it possible, and if so, how, to embed discrete real time in generally distributed process theories? Additionally, (4) is the abstraction using the weak behavioral equivalence in Markovian process theories (and other modeling formalisms as well) performance pre- serving, and is such an approach compositional? In the end, (5) how can we do performance analysis using discrete-time and probabilistic choices? The contents of the thesis is as follows. First, we introduce the central concept of a race condition that de¯nes the interaction between stochastic timed delays. We introduce a new type of race condition, which enables the synchronization of stochastic delays with the same sample as in timed process theories. This gives the basis for the notion of a timed delay in a racing context, which models the expiration of stochastic delays. In this new setting, we de¯ne a strong bisimulation relation that deals with the (probabilistic) race condition on a symbolic level. Next, we show how to derive stochastic delays as guarded recursive speci¯cation involving timed delays in a racing context and we derive a ground-complete stochastic-time process theory. Then, we take the opposite viewpoint and we develop a stochastic process theory from scratch, relying on the same interpretation of the race condition. We embed real time in the stochastic-time setting by using context-sensitive interpolation, a restricted notion of time additiv- ity. Afterwards, we turn to Markovian process theories and we show com- positionality of the Markov reward chains with fast and silent transitions with respect to lumping-based and reduction-based aggregation methods. These methods can be used to show preservation of performance measures when eliminating probabilistic choices and non-deterministic silent steps in Markovian process theories. Then, we specify the underlying model of prob- abilistic timed process theories as a discrete-time probabilistic reward graph and we show its transformation to a discrete-time Markov reward chain. The approach is illustrated by extending the environment of the modeling language Â. The developed theories are illustrated by specifying a version of the concurrent alternating bit protocol and analyzing it in the  toolset