Business Semantics Centric Reliability Testing for Web Services in BPEL

Testing service orchestrations is a challenging research domain due to necessity of additional testing efforts, complementing traditional software testing. Although various testing approaches and tools have been proposed, most of them provide partial solutions covering single testing activities such as test path analysis, test case generation, Web service emulation, fault injection and so on. Following the current research direction, we have developed an integrated testing framework, called TASSA, which aims to provide end-to-end testing of Business Process Execution Language (BPEL) orchestrations. This paper introduces its core capability for automation of test cases generation, execution and management implemented in an open source tool for WSDL-based testing of both single Web services and composite Web services, described with BPEL. The tool's functionality includes identification of web service operations as well BPEL variables in case of service composition testing, generation of SOAP request templates, data driven testing, definition of assertions at different levels (HTTP, SOAP and BPEL variable), execution and management of test cases.

The Business Process Execution Language (BPEL) is now a de facto standard for specifying and executing business process for web service composition and orchestration. As more and more web services are composed using BPEL, tuning these compositions and gain better performance becomes increasingly important. This paper presents our approach for optimizing the BPEL process and introduces OptBPEL, a tool for performance optimization of BPEL process. The approach starts from the optimization of synchronization structure concerning link in BPEL. After that, some concurrency analysis techniques are applied to obtain further performance improvement. Finally, we give some experiments and prove the efficiency of these optimization algorithms used in OptBPEL.

The concept of software as a service has been increasingly adopted to develop distributed applications. Ensuring the reliability of loosely coupled compositions is a challenging task because of the open, dynamic, and independent nature of composable services; this is especially true when the execution of a service-based process relies on independent but correlated services. Transactions are the prototypical case of compositions spanning across multiple services and needing properties to be valid throughout the whole execution. Although transaction protocols and service composition languages have been proposed in the past decade, a true viable and effective solution is still missing. In this article, we propose a systematic aspect-based approach to integrating transactions into service compositions, taking into account the well-known protocols: Web Service Transaction and Business Process Execution Language (BPEL). In our approach, transaction policies are first defined as a set of aspects. They are then converted to standard BPEL elements. Finally, these transaction-related elements and the original BPEL process are weaved together, resulting in a transactional executable BPEL process. At runtime, transaction management is the responsibility of a middleware, which implements the coordination framework and transaction protocols followed by the transactional BPEL process and transaction-aware Web services. To automate the proposed approach, we developed a supporting platform called Salan to aid the tasks of defining, validating, and weaving aspect-based transaction policies, and of deploying the transactional BPEL processes. By means of a case study, we demonstrate the proposed approach and evaluate the performance of the supporting platform. Experimental results show that this approach is effective in producing reliable business processes while reducing the need for direct human involvement.

Business Process Execution Language (BPEL) has been popularly used to describe a collaborative business processes which is executed by Web services. However, the original BPEL language is defined in a strict format which the developers must follow. This leads to difficulties to create or modify the BPEL documents. In order to overcome the problem, the original BPEL has been extended to an annotated-BPEL so that BPEL documents can be freely modified. One of the applications of annotated-BPEL is that it is employed to describe "request" Web service information. Since Web service discovery systems may support different Web service description languages, annotated BPEL must be translated into specific description languages so that it can be readable and understood. This paper introduces a system that generates "request" Web services from the annotated BPEL. The system supports the two most popular Web services description languages, namely, OWL-S and WSDL. The description is first translated into OWL-S since it contains semantics in describing the service. This is done by searching 'the best matched' OWL concepts in a OWL repository and then filling these concepts into an predefined OWL-S template. If we cannot find any suitable concepts, a WSDL document will be generated.

Web services technology is the most common implementation of service oriented architecture. Web services are based on open technologies such as eXtensible Markup Language (XML) and offer a distributed approach for the integration of heterogeneous applications across the internet. The process of combining web services functionalities into one composite service is called web services composition. To perform this task, several languages such as Business Process Execution Language (BPEL), Web Services Flow Language (WSFL) and Web Service Choreography Interface (WSCI) have emerged. These languages are based on programming concepts and neglect the specification step which is very important in any software development process. In this paper, we address the formal specification of web services descriptions and the modelling of their composition using the model driven engineering principles. To this end, we propose a domain specific language (DSL) called S-GNet. The proposed DSL introduces new modelling elements which make it well adapted to the web services characteristics. We also propose a graph grammar which transforms Web Services Description Language (WSDL) descriptions into their equivalent S-GNet specifications. This grammar is integrated within an S-GNet modelling tool.

RESTful Web service composition with BPEL for REST

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.

Technologies for Web services facilitate the creation of business process solutions in an efficient, standard way. However, the automation of process integration with Web service technologies requires the automation of discovery and composition of Web services. In this paper, we focus on two problems of the Web service-based business process integration: (1) the discovery of Web services based on the capabilities and properties of published services, and (2) the composition of business processes based on the business requirements of submitted requests. We propose a solution to these problems, which comprises multiple matching algorithms, a micro-level matching algorithm, which matches the capabilities of services with activities in a process request, and macro-level matching algorithms, which are used to compose a business process by identifying services that satisfy the business requirements and constraints of the request. The solution from the macro-level matching algorithms is optimal in terms of meeting a certain business objective, e.g., minimizing the cost or execution time, or maximizing the total utility value of business properties of interest. Numerical examples are illustrated to show how to select the best Web service candidate for a chosen business process through the use of proposed macro-level matching algorithms. Furthermore, we show how existing Web service standards, UDDI and BPEL4WS, can be used and extended to specify the capabilities of services and the business requirements of requests, respectively.

The Business Process Modeling Notation (BPMN) was developed by an international body called the Business Process Management Initiative (BPMI). The strengths of BPMN include that it is easily readable and understandable, and could be transformed into the current widely used business process implementation language, the Business Process Execution Language (BPEL). However, there are some fundamental incompatibilities between BPMN and BPEL, which make it difficult to generate BPEL code for implementation from BPMN models.The aim of this paper is to investigate the synergic uses of BPMN and BPEL to model and implement executable business processes. To that end, we propose a Business Process Modelling framework. Then we apply it to a real life business process scenario involving a typical manufacturing process in the automotive industry. From the case study, we are able to conclude that BPMN is suitable for modelling business processes and then implementing the model in BPEL in spite of the incompatibilities between the former and the latter.

Web service composition refers to the process of combining several value-added services. It has received much interest in enterprise applications. Web Service Choreography Description Language (WSCDL) is a W3C specification for the description of peer-to-peer collaborations of participants from a global viewpoint. As an XML-based language aimed to become a Web service composition standard for choreography, WSCDL may clarify the opaque points, detect and repair design errors in the language definition, yet provide the theoretical grounding for relative tools development. Petri net is a first-class formal modeling tool that has been widely used in many fields. Based on a Petri net, this paper proposed a formal model that can be used to clarify the semantics of WSCDL and verify some relative properties throughout. The model helps analyze the semantic compatibility between a business process specified in Business Process Execution Language (BPEL) and a WSCDL process.

Web services composition is an emerging paradigm for application integration within and across organizations and enterprises. A set of languages and techniques for web services composition has emerged and is continuously being enriched with new proposals from different vendors. Among these languages we remind Business Process Execution Language (BPEL) which emphasizes the importance of modelling and simulating of business process in Web Services composition. Multi-agent Systems (MAS) are composed of autonomous agents that interact and coordinate to achieve their intentions. This makes them particularly adapted to modelling composite and complex information systems. In this paper we propose a new approach for modeling and simulating the process of web services composition using the Multi-Agent Reactive Decisional System (MARDS) Model and BPEL Language.

As the capability of an individual Web service is limited, it's necessary to create new functionalities with existing Web services. Web services composition is the ability to create a new value-added service by incorporating some existing Web services together. An important challenge for Web services composition is how to ensure the correctness and reliability of the WS-BPEL (Web services business process execution language) process and the composition. A graphical and formal modeling tool suitable for solving this problem is CPN (Colored Petri net), which provides formal semantics and a number of analysis techniques for modeling and verifying web services composition. This paper proposes a CPN-based model for web services composition, describes how to translate WS-BPEL to CPN model, and discusses the analysis and verification of services composition. The model enables efficient composition of Web services and validates the correctness of composition by formal verification.

Managing Service Level Agreement (SLA) for composite semantic web services is a very complex process, as it involves many complex tasks such as components discovery, provisioning, monitoring, recovery, and coordination. Indeed, managing all these tasks manually is a very cumbersome operation, nevertheless it is time consuming and prone to errors. To overcome such problems, automated SLA management for composite semantic web services is needed. This requires the SLA of the composite service to be described in a machine-understandable format such that it can be understood and processed by the automated SLA management tool. Currently, there is no SLA description language for composite semantic web services, but there exists an SLA description language for atomic web services, known as the Web Service Level Agreement (WSLA). Hence, in this paper, we aim to extend the WSLA language to describe composite semantic web services' SLAs, then we show how we can automatically generate the components' SLAs from the composite semantic web services' SLAs; adopting the CRECENT framework that we previously proposed for managing composite web services.

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.

An emerging technology like business process execution language (BPEL) and its implementation in BPEL for Web services (BPEL4WS) gives extra possibilities in describing business processes. It further adheres, as a technology, in a consistent way to the underlying Web service-based implementation technology and is a perfect fit for service-oriented architectures (SOA) as they are currently implemented throughout organizations as a successor to enterprise application integration (EAI). However, BPEL4WS, in its current implementation, will only serve in a static way for production workflows. In this chapter we discuss how Semantic Web services through a semantic service-oriented architecture (SSOA) can be used to extend BPEL4WS to create ad hoc and collaborative workflows.