A Petri Nets based functional validation for services composition

In service-oriented architecture (SOA), quality of service is hidden to service consumers due to the blackbox nature of SOA. In a service composition, low quality of an atomic service may cause the quality degradation of all its successors in a service composition. Hence, quality management of a service is important in SOA environment. For this, definition of a quality model especially considering the consumers' perspective is a prerequisite since consumers are the first class users of the services. Therefore, this paper proposes a quality model for evaluating services in SOA regarding customers' perspective. We first analyze the service quality requirements and define quality attributes of the quality model. Then we define metrics for each quality attribute. To show the applicability and usefulness of the quality model, we perform a case study for flight ticket reservation service and finally perform a theoretical analysis.

Online services encapsulate enterprises, people, software systems and often operate in poorly understood environments. Using such services in tandem to predictably orchestrate a complex task is one of the principal challenges of service-oriented computing. A composite service orchestration soliciting multiple atomic services is plagued by a number of sources of variation. For instance, availability of an atomic service and its response time are two important sources of variation. Moreover, the number of possible variations in a composite service increases exponentially with increase in the number of atomic services. Testing such a composite service presents a crucial challenge as its often very expensive to exhaustively examine the variation space. Can we effectively test the dynamic behavior of a composite service using only a subset of these variations? This is the question that intrigues us. In this paper, we first model composite service variability as a feature diagram (FD) that captures all valid configurations of its orchestration. Second, we apply pairwise testing to sample the set of all possible configurations to obtain a concise subset. Finally, we test the composite service for selected pairwise configurations for a variety of QoS metrics such as response time, data quality, and availability. Using two case studies, Car crash crisis management and eHealth management, we demonstrate that pairwise generation effectively samples the full range of QoS variations in a dynamic orchestration. The pairwise sampling technique eliminates over 99% redundancy in configurations, while still calling all atomic services at least once. We rigorously evaluate pairwise testing for the criteria such as: a) ability to sample the extreme QoS metrics of the service b) stable behavior of the extracted configurations c) compact set of configurations that can help evaluate QoS tradeoffs and d) comparison with random sampling.

In recent years, the use of distributed systems by software industries and academic organizations has been increased in many folds. Therefore, the web services and a service-oriented style of architecture becomes the basis for a new generation of distributed applications and system management tools. Web Services and Service-Oriented Architecture (SOA) play a significant role as a middleware for software interoperability. These technologies deploy practice for ebusiness or Enterprise Application Integration (EAI). With the success of such deployments, Quality of Service (QoS) properties such as response time, availability and service costs are in high demands for SOA-based interoperability. A service composition in Service Oriented Architecture (SOA) environment is developed dynamically by integrating services from various service providers. There may be situations where services become faulty, resulting in violation of end to end Quality of Service (QoS) constraints. This paper proposes an approach to overcome this problem of faulty service reconfiguration. The work focuses on identifying the faulty services and their replacement on the basis of QoS constraints. In spite of modifying the whole composition, reconfiguration to the faulty region shall reduce the overheads of computations and service distractions in service delivery. The proposed approach presented in this paper is compared with various other prevalent service composition strategies.

Service Oriented Architecture (SOA) refers to an architectural paradigm that describes how organizations, people and systems provide and use services to achieve their goals. Moreover, with the evolution of SOA, the focus in software development has shifted from applications to reusable services. Besides, reuse in SOA has more focused on service composition rather than reuse of existing implementations to build new services with additional functionalities. The preferred way to realize SOA remains web services which explain our interest in promoting reuse of Web services by managing variability. In this paper, we propose a model driven method for managing Web service's variability based on MDA (Model Driven Architecture). In fact, through MDA, the method enables the automation of Web service's realization regardless of the supported platforms. Moreover, we present a WSDL extension meta-model called VarWSDL which enhances Web services by variability notions. That permits Web services reuse.

Many application domains are increasingly leveraging service-oriented architecture (SOA) techniques to facilitate rapid system deployment. Many of these applications are time-critical and, hence, real-time assurance is an essential step in the service composition process. However, there are gaps in existing service composition techniques for real-time systems. First, admission control is an essential technique to assure the time bound for service execution, but most of the service composition techniques for real-time systems do not take admission control into account. A service may be selected for a workflow during the composition phase, but then during the grounding phase, the concrete service may not be able to admit the workload. Thus, the entire composition process may have to be repeated. Second, communication time is an important factor in real-time SOA, but most of the existing works do not consider how to obtain the communication latencies between services during the composition phase. It is clear that maintaining a full table of communication latencies for all pairs of services is infeasible. Obtaining communication latencies between candidate services during the composition phase can also be costly, since many candidate services may not be used for grounding. Thus, some mechanism is needed for estimating the communication latency for composite services. In this paper, we propose a three-phase composition approach to address the above issues. In this approach, we first use a highly efficient but moderately accurate algorithm to eliminate most of the candidate compositions based on estimated communication latencies and assured service response latency. Then, a more accurate timing prediction is performed on a small number of selected compositions in the second phase based on confirmed admission and actual communication latency. In the third phase, specific concrete services are selected for grounding, and admissions are actually performed. The approach is scalable and can effectively achieve service composition for satisfying real-time requirements. Experimental studies show that the three-phase approach does improve the effectiveness and time for service composition in SOA real-time systems. In order to support the new composition approach, it is necessary to effectively specify the needed information. In this paper, we also present the specification model for timing-related information and the extension of OWL-S to support this specification model.

With the increasing volume of data to be analysed, one of the challenges in Service Oriented Architecture (SOA) is to make web services efficient in processing large-scale data. Parallel execution and cloud technologies are the keys to speed-up the service invocation. In SOA, service providers typically employ policies to limit parallel execution of the services based on arbitrary decisions. In order to attain optimal performance improvement, users need to adapt to the services policies. A composite service is a combination of several atomic services provided by various providers. To use parallel execution for greater composite service efficiency, the degree of parallelism (DOP) of the composite services need to be optimized by considering the policies of all atomic services. We propose a model that embeds service policies into formulae to calculate composite service performance. From the calculation, we predict the optimal DOP for the composite service, where it attains the best performance. Extensive experiments are conducted on real-world translation services. We use several measures such as mean prediction error (MPE), mean absolute deviation (MAD) and tracking signal (TS) to evaluate our model. The analysis results show that our proposed model has good prediction accuracy in identifying optimal DOPs for composite services.

With the increasing adoption of the web-services stack of standards, service-oriented architecture has attracted substantial interest from the research community which has produced several languages and methods for describing and reasoning about services. These languages cover many concepts ranging from individual services and their code generation from specifications, service semantics, service compositions and networks, economics and business aspects around service ecosystems etc. However, this abundance of specification languages has also resulted in communication difficulties between stakeholders and hinders tasks such as service composition, discovery and maintenance. The presented work is a step towards the unification of the specifications and different aspects of service systems using Model-Driven Engineering. We propose a generic and abstract web service meta-model called WSMeta, which has the ability to describe both operation-centric web services (WS-*) and data-centric web services (REST) and can be used in tasks such as service evolution analysis and service systems maintenance.

Architectural mismatch; the semantic and syntactic gap preventing component composition, can be partially alleviated through the ubiquity of the protocols for service composition (syntax). And yet, the semantics of service or component composition have remained elusive. The contribution of this paper builds on the notions introduced by grammar-oriented object design (GOOD) using the notion of manners to specify the semantics of services and drive their automated composition through dynamically reconfigure architectures enabled through GOOD. This leads to the use of manners for explicit service semantics representation in a re-configurable architectural style. We describe the base requirements for automated component and services composition and show how automated assembly of components and services can be accomplished through a dynamically reconfigurable (DyRec) architectural style. In addition, we show how this vision of dynamic reconfiguration is naturally supported by the Web services framework, because it derives from some of the core requirements of the service oriented architectures (SOA) style embodied by Web services. Further, we discuss how such a DyRec architectural style can be implemented using grammar-oriented object design (GOOD) and describe a project that led to a tool called the Business Compiler, to accomplish dynamic composition and collaboration.

Enterprise application integration makes data sharing easier, efficient and provides flexibility for organizations to seize opportunities and respond to stakeholder needs. Faculty of Mathematics and Natural Sciences (FMIPA) Tanjungpura University is an organization that wants to apply information technology effectively to support its business processes. Currently the application at FMIPA is built with different platforms and databases so that it cannot be integrated to share data between parts of the organization. FMIPA intends to build a service-oriented technology architecture to support the realization of organizational goals. SOA (Service Oriented Architecture) can be used as a framework for enterprise application integration. SOA adoption is often not as expected because organizations do not plan their processes comprehensively. It is necessary to measure the maturity level of the organization's SOA adoption so that the current state of the organization's SOA and future expectations can be found. ISO/IEC 16680 (OSIMM) is a method for measuring the SOA maturity level with 7 levels of maturity and 7 dimensions. To expedite the SOA adoption process in FMIPA, SOA maturity level was measured using ISO/IEC 16680. Based on measurements of the seven dimensions of SOA at ISO/IEC 16680, it was found that the current level of SOA adoption maturity (As-Is) at FMIPA Untan was at the level one (Silo), while the expected maturity level (To-Be) is level four (Service). Gap analysis then carried out related to the gap in maturity levels, and is followed by making recommendations dan roadmap for SOA adoption.

Summary Interoperability and componentization are the two defining characteristics of Service Oriented Architectures (SOA). From a middleware perspective this means standardized quality of service (QoS) protocols and QoS-rich service descriptions. This paper provides an architectural overview of quality of service issues in SOA environments and a review of open problems and current research directions.

Service composition is an aggregate of services often leveraged to automate the enterprise business processes. While Service Oriented Architecture (SOA) has been a forefront of service composition, services can be realized as efficient distributed and parallel constructs such as MapReduce, which are not typically exploited in service composition. With the advent of Software-Defined Networking (SDN), global view and control of the entire network is made available to the networking controller, which can further be leveraged in the application level. This paper presents FIRM, an approach for Software-Defined Service Composition by leveraging SDN and MapReduce. FIRM comprises Find, Invoke, Return, and Manage, as the core procedures in achieving a QoS-Aware Service Composition.

Service Oriented Architecture (SOA) introduced the web services as distributed computing components that can be independently deployed and invoked by other services or software to execute composite services that represent an end-to-end business process. An important problem in the SOA is the web service selection and composition problem which involves selecting the right web services mix to construct the best service composition that achieves the consumers Service Level Agreement (SLA) requirements. In this chapter we propose different methods to solve the problem of the business processes execution engine web service selection and services composition construction in the Service Oriented Architecture (SOA).  The chapter provides different mechanisms to improve the web services selection and composition using dynamic techniques. The main goal is to satisfy the services' requirements expressed as the SLA and to enhance the services selection and composition by increasing the availability and decreasing the response time of the service compositions.

Service composition in service oriented architecture is an important activity. In regard to achieve the quality of service and secured activities from the web service compositions, they need to be verified about their impact towards fault proneness before deploying that service composition. Henceforth, here in this paper, we devised set of exploratory metrics, which enables to assess the services by multi objective QOS factors. These devised explorative measures reconnoitres the higher and lower ranges of the SCFI, which is from the earlier compositions that are notified as either fault inclined or hale. The experimental results explored from the empirical study indicating that the devised metrics are significant towards estimating the state of given service composition is fault tending or hale.

In Service-Oriented Architecture (SOA), applications can be assembled by a set of existing distributed services spanning across organizations and platforms. SOA increases reuse and cooperation among services. Therefore, applications can be built in a rapid way with relatively low cost. With the increasing adoption of SOA solutions to application integration, the ability to compose services efficiently and effectively becomes more and more important. A lot of efforts have been devoted to service composition. Service composition integrates existing reusable services together as a process to fulfill business requirements, and exposes the process as a service (i.e., composite service). Specifically, a composition process involves the following five steps: 1. Specify business requirements: A requirement (e.g., purchase a book online) for composing services could be a declarative expression using formal or informal languages, an abstract process model (e.g., a business process model), or design models (e.g., UML diagrams). 2. Provide service description: Service description specifies the capability of services, such as inputs/outputs, exceptions, functional and non-functional description. 3. Discover relevant services: Service discovery is the process of locating a service that meets a certain searching criteria. For example, we search for an appropriate service to offer forecasting service. The searching criteria for the service discovery could be specified using keywords, such as weather forecast. 4. Generate composition process model: A composition process model contains a set of selected services, control flows and data flows among those services. Standards, such as BPEL (Business Process Execution Language), are used to formally specify process models. A business requirement usually cannot be fulfilled by a single service. Various services are integrated using composition process models. 5. Evaluate composition results: It is quite common that many returned services have the same or similar functionalities. It leads to more than one composition result to fulfill the business requirements. The different composition results can be evaluated to select the best one that meets the functional and nonfunctional requirements.

In this paper, Petri nets are used to model the different components of service composition, and form the energy consumption model of service composition based on the relationship between components, Agent is also introduced in the energy consumption management process. Then, an adaptive energy consumption strategy are proposed to dynamically ensure that service composition can get the lowest energy consumption. The operational semantics and related theories of Petri nets help establish the correctness of our proposed method. We have also performed two simulations to evaluate our proposed approach. Results show that it can help reveal the structural and behavioral characteristics of energy consumption in service composition. Index Terms—Service composition, Agent, Petri nets, energy consumption