A Cooperative Service Composition Language and Its Formal Semantics

Nowadays, service oriented architecture has been given strong attention as an important approach to integrate heterogeneous systems, in which complex services are created by composing simpler services offered by various systems. The correctness of composition requires techniques to verify if the composite service behaves properly. To this end, in this paper we propose a new method for runtime monitoring of composite services which uses Communicating Sequential Processes (CSP) to specify properties formally. Then, the CSP specification of properties is translated to a Labeled Transition System (LTS). In order to verify the safety of a composite service, we traverse the generated LTS at runtime. Existing methods almost use temporal logic to specify safety properties. There are two advantages in using CSP: 1) similarity of CSP operators and service composition patterns makes CSP straightforward to be used by users. 2) there are some properties which can not be specified by temporal logic, while they can be expressed using CSP.

A Study On The Potential Active Names of π-Agents

PROMELA is a high level modeling language for model checking purpose. PROMELA model can be checked using SPIN (Simple PROMELA Interpreter) model checker to ensure formally some specifications hold in the model. However, PROMELA does not have formal and clear semantics. It is interpreted under SPIN implementation only and thus is bounded into SPIN. With high-level language it has, PROMELA has gain fame in model checker world due to its easiness to capture process model using high level language. Describing PROMELA formal semantic is a good way to broaden PROMELA usage. One of PROMELA feature is the ability to model concurrent processes, in which the concurrent process may not start from the same time point. This feature, called dynamic process creation, is essential to be noticed, to ensure that state-transition of PROMELA model is correct. Dynamic process creation in PROMELA should be defined formally, we use Labeled Transition Systems (LTSs) to describe formal semantic of PROMELA dynamic process creation.

Wireless sensor networks (WSNs) are expected to run unattendedly for critical tasks. To guarantee the correctness of WSNs is important, but highly nontrivial due to the distributed nature. In this work, we present an automatic approach to directly verify WSNs built with TinyOS applications implemented in the NesC language. To achieve this target, we firstly define a set of formal operational semantics for most of the NesC language structures for the first time. This allows us to capture the behaviors of sensors by labelled transition systems (LTSs), which are the underlying semantic models of NesC programs. Secondly, WSNs are modeled as the composition of sensors with a network topology. Verifications of individual sensors and the whole WSN become possible by exploring the corresponding LTSs using model checking. With substantial engineering efforts, we implemented this approach in the tool NesC@PAT to support verifications of deadlock-freeness, state reachability and temporal properties for WSNs. NesC@PAT has been applied to analyze and verify WSNs, with unknown bugs being detected. To the best of our knowledge, NesC@PAT is the first model checker which takes NesC language as the modeling language and completely preserves the interrupt-driven feature of the TinyOS execution model.KeywordsWireless Sensor NetworkModel CheckerOperational SemanticLinear Temporal LogicState ReachabilityThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

In software markets of the future, customer-specific software will be developed on demand based on distributed software and hardware services. Based on a customer-specific request, available service offers have to be discovered and composed into sophisticated IT services that fulfill the customer's request. A prerequisite of this vision are rich service descriptions, which comprise structural as well as behavioral aspects of the services, otherwise an accurate service discovery and composition is not possible. However, automatic matching of service requests and offers specified in rich service descriptions for the purpose of service discovery is a complex task, due to the multifaceted heterogeneity of the service partners. This heterogeneity includes the use of different specification languages, different underlying ontologies, or different levels of granularity in the specification itself. In this article, we present a comprehensive approach for service discovery and composition, which overcomes the underlying heterogeneity of the service partners. Based on a realistic case study of our industrial partner from the e-tourism domain, we first introduce an automatic matching mechanism for service requests and offers specified in a rich service description language. In addition, we propose an automatic service composition approach, which determines possible service compositions by composing the service protocols through a composition strategy based on labeled transition systems.

The paper presents the design and implementation of ARC-a tool for automated verification of concurrent systems. The tool is based on the untimed CSP language, its semantic models and theory of refinement. We alleviate the combinatorial explosion problem using ordered binary decision diagrams (OBDDs) for the internal representation of complex data structures-sets and labeled transition systems (LTS). The semantically complex external choice operator is translated into the corresponding LTS using an optimized algorithm. This and some other implementation improvements allow verifying systems with up to 10/sup 33/ states, which is consistent with the capabilities of other OBDD based approaches. Compared to two existing CSP tools, FDR and MRC, ARC has fewer language restrictions and is more memory efficient. A performance comparison based on the n-schedulers and dining philosophers problems suggests that the checking algorithm of ARC is, in most cases, faster than those of the other tools.

We propose a Calculi in process algebraic framework to formally model Intrusion Detection System (IDS) for secure routing in Mobile Ad-hoc Networks. The proposed calculi, named as dRi, is basically an extension of Distributed pi calculus (Dpi). The calculi models unicast, multicast & broadcast communication, node mobility, energy conservation at node and detection of malicious node(s) in Mobile Ad-hoc Networks. The Calculi has two syntactic categories: one for describing nodes and another for processes which reside in nodes. We also present two views of semantic reductions; one as reduction on configurations whereas another as LTSs (Labelled Transition Systems), behavioural semantics, where reduction on configurations are described on various actions. We present an example described using LTSs to show the capability of the proposed calculi. We define a bisimulation based equivalence between configurations. Further we define a touch-stone equivalence on its reduction semantics & also present prove outline for bisimulation based equivalence that can be recovered from its touch-stone equivalence and vice-versa.

Today’s trend in Web engineering is the automation of Web service interoperation. With this aim, web content is noted with semantic information, using Web Semantic languages. Web Services is becoming the leading technology that provides functionality of an enterprise. This functionality carries out the activities that form a process. Business processes are a set of activities that can be seen as offered business services. Therefore, this article presents a process to derive web services specifications and service composition from business models. The paper considers DAML-S as the web services markup language to represent the description of web services and specify their composition. Rational Unified Process business model is the language used as input. The article shows the set of derivation rules that allows the atomatic generation of DAML-S modules from business models.

The Web service composition problem involves the creation of a choreographer that provides the interaction between a set of component services to realize a goal service. Several methods have been proposed and developed to address this problem. In this paper, we consider those scenarios where the composition process may fail due to incomplete specification of goal service requirements or due to the fact that the user is unaware of the functionality provided by the existing component services. In such cases, it is desirable to have a composition algorithm that can provide feedback to the user regarding the cause of failure in the composition process. Such feedback will help guide the user to re-formulate the goal service and iterate the composition process. We propose a failure analysis technique for composition algorithms that views Web service behavior as multiple sequences of input/output events. Our technique identifies the possible cause of composition failure and suggests possible recovery options to the user. We discuss our technique using a simple e-Library Web service in the context of the MoSCoE Web service composition framework.KeywordsFailure AnalysisService CompositionComposite ServiceLabel Transition SystemComposition ProcessThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

With web services growing and accumulating in application area, service discovery has become a hot issue for service composition and service management. Service clustering provides a promising way to split the whole searching space into small regions so as to minimize the discovery time effectively. However, semantic information is a critical element during the whole disposing process. Current industrialized Web Service Description Language (WSDL) does not contain enough information for service description. Therefore, a service clustering method has been proposed, which enhances original WSDL document with semantic information by means of Linked Open Data (LOD). Experiment based on real service data has been performed, and comparison with similar methods has also been provided to demonstrate the effectiveness of the method. It is shown that utilizing semantic information from LOD enhances the precision of service clustering. And it forms a sound base for further comprehensive processing with semantic information.

In this paper, we present a Maude-based tool for embedded systems specification, performance estimation and formal verification of some properties. In our case, the application is modeled as a network of concurrent tasks with coarse grained actions (CGAs) that communicate with each other via abstract channels following Kahn Process Networks (KPNs) model of computation semantics. In order to achieve high level performance estimation, the hardware architecture should be abstracted too. Consequently, each hardware component of the architecture is parameterized by a set of abstract parameters matching the abstraction level of the application.

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Service-oriented computing (SOC) is an emerging paradigm of system design and aims at replacing complex monolithic systems by a composition of interacting systems, called services. A service encapsulates self-contained functionality and offers it over a well-defined, standardized interface. This modularization may reduce both complexity and cost. At the same time, new challenges arise with the distributed execution of services in dynamic compositions. In particular, the correctness of a service composition depends not only on the local correctness of each participating service, but also on the correct interaction between them. Unlike in a centralized monolithic system, services may change and are not completely controlled by a single party. We study correctness of services and their composition and investigate how the design of correct service compositions can be systematically supported. We thereby focus on the communication protocol of the service and approach these questions using formal methods and make contributions to three scenarios of SOC. The correctness of a service composition depends on the correctness of the participating services. To this end, we (1) study correctness criteria which can be expressed and checked with respect to a single service. We validate services against behavioral specifications and verify their satisfaction in any possible service composition. In case a service is incorrect, we provide diagnostic information to locate and fix the error. In case every participating service of a service composition is correct, their interaction can still introduce problems. We (2) automatically verify correctness of service compositions. We further support the design phase of service compositions and present algorithms to automatically complete partially specified compositions and to fix incorrect compositions. A service composition can also be derived from a specification, called choreography. A choreography globally specifies the observable behavior of a composition. We (3) present an algorithm to deduce local service descriptions from the choreography which—by design—conforms to the specification. All results have been expressed in terms of a unifying formal model. This not only allows to formally prove correctness, but also makes results independent of the specifics of concrete service description languages. Furthermore, all presented algorithms have been prototypically implemented and validated in experiments based on case studies involving industrial services.

In the past a few years, the Web has undergone a tremendous change towards a highly user-centric environment. Millions of users can participate and collaborate for their own interests and benefits. Service oriented computing and Web services have created great potential opportunities for the users to build their own applications. Then, it is a pressing issue that, the users can compose services without too complex tasks and efforts. In this paper, we introduce a user-oriented approach which aims to simplify service composition. We leverage the plentiful information residing in service tags, both from service descriptions (such as WSDL) and the annotations tagged by users. Employing some mining algorithms, a direct acyclic graph is built up to represent potential composition opportunities. With a simple and intuitive search, it allows users to explore the space of potentially composable services and achieve service composition in a heuristic manner. We have developed a composition advisor to provide recommendations guiding and assisting the users. It also lets the users discover and make use of services without having to understand too many details of individual candidate services. To enable the users to accomplish service composition in a more interactive access channel, we finally provide a user-friendly prototype based on Web browsers. It undoubtedly reduces the complexity and lowers the entry barrier for the users, and makes them better play their role in the service-oriented Web environment.

Statechart diagrams provide a graphical notation for describing dynamic aspects of system behaviour within the Unified Modelling Language (UML). In this paper, we present a branching-time model-checking approach to the automatic verification of the formal correctness of UML Statechart diagram specifications. We use a formal operational semantics for building a labelled transition system (automaton) which is then used as a model to be checked against correctness requirements expressed in Action-Based Temporal Logic (ACTL). Our reference verification environment is JACK, where automata are represented in a standard format, which facilitates the use of different tools for automatic verification.