From Coordination to Stochastic Models of QoS

Abstract

Science. It is sponsored by the Netherlands Organisation for Scientific Research (NWO).CWI is a founding member of ERCIM, the European Research Consortium for Informatics and Mathematics.CWI's research has a theme-oriented structure and is grouped into four clusters. Listed below are the names of the clusters and in parentheses their acronyms. From coordination to stochastic models of QoS ABSTRACT Reo is a channel-based coordination model whose operational semantics is given by Constraint Automata (CA). Quantitative Constraint Automata extend CA (and hence, Reo) with quantitative models to capture such non-functional aspects of a system's behaviour as delays, costs, resource needs and consumption, that depend on the internal details of the system. However, the performance of a system can crucially depend not only on its internal details, but also on how it is used in an environment, as determined for instance by the frequencies and distributions of the arrivals of I/O requests. In this paper we propose Quantitative Intentional Automata (QIA), an extension of CA that allow incorporating the influence of a system's environment on its performance. Moreover, we show the translation of QIA into ContinuousTime Markov Chains (CTMCs), which allows us to apply existing CTMC tools and techniques for performance analysis of QIA and Reo circuits. Abstract. Reo is a channel-based coordination model whose operational semantics is given by Constraint Automata (CA). Quantitative Constraint Automata extend CA (and hence, Reo) with quantitative models to capture such non-functional aspects of a system's behaviour as delays, costs, resource needs and consumption, that depend on the internal details of the system. However, the performance of a system can crucially depend not only on its internal details, but also on how it is used in an environment, as determined for instance by the frequencies and distributions of the arrivals of I/O requests. In this paper we propose Quantitative Intentional Automata (QIA), an extension of CA that allow incorporating the influence of a system's environment on its performance. Moreover, we show the translation of QIA into Continuous-Time Markov Chains (CTMCs), which allows us to apply existing CTMC tools and techniques for performance analysis of QIA and Reo circuits. Probability, Networks and Algorithms (PNA)SoftwareKeywords: Performance evaluation, Coordination language, Reo, MarkovChains. IntroductionService-oriented Computing (SOC) provides the means to design and deploy distributed applications that span organization boundaries and computing platforms by exploiting and composing existing services available over a network. Services are platform-and network-independent applications that support rapid, low-cost, loosely-coupled composition. Services run on the hardware of their own providers, in different containers, separated by fire-walls and other ownership and trust barriers. Their composition requires additional mechanisms (e.g., process work-flow engines, connectors, or glue code) to impos...

Reo + mCRL2 : A framework for model-checking dataflow in service compositions

“…This approach is compliant with the two principles introduced in [8], namely, that (i) a data-flow in a channel takes place from its input port to its output port, and (ii) mixed nodes receive and send data instantaneously. Thus, ACA is a suitable compositional model for reasoning about dataflow in Reo circuits with timed delays.…”

“…A number of semantic models of Reo, most notably, constraint and intentional automata, have been extended with the information to capture the QoS characteristics of the channels and their composition metrics [9,8]. However, these extensions assume that the QoS characteristics do not affect the behavior of a circuit.…”

On the reconfiguration of software connectors

“…Moreover, it makes sense to continue working on the hybrid logic presented here by extending it to deal with properties of paths within a coordination pattern and incorporating quantitative measures to express QoS constraints. We are currently working on this topic taking into account, on a reconfiguration, suitable measures of QoS levels attached to coordination patterns [2] and to their deployment context. Relevant related work includes research on Stochastic Reo [18] and on a generic QoS algebra [7,19,17].…”

Coordinating Multicore Computing

“…Reo has been used for composition of Web services [16,57,65], modeling and analysis of long-running transactions in service-oriented systems [60], coordination of multi-agent systems [10], performance analysis of coordinated compositions [12,13,17,70,71], modeling of business processes and verification of their compliance [14,59,73], and modeling of coordination in biological systems [31].…”