Formal semantics and analysis of control flow in WS-BPEL

Web service composition refers to the creation of new (Web) services by combination of functionality provided by existing ones. This paradigm has gained significant attention in the Web services community and is seen as a pillar for building service-oriented applications. A number of domain-specific languages for service composition have been proposed with consensus being formed around a process-oriented language known as WS-BPEL (or BPEL). The kernel of BPEL consists of simple communication primitives that may be combined using control-flow constructs expressing sequence, branching, parallelism, synchronisation, etc. As a result, BPEL process definitions lend themselves to static flow-based analysis techniques. In this report, we describe a tool that performs two useful types of static checks and extracts meta-data to optimise dynamic resource management. The tool operates by translating BPEL processes into Petri nets and exploiting existing Petri net analysis techniques. It relies on a comprehensive and rigorously defined mapping of BPEL constructs into Petri net structures

Formal semantics and analysis of control flow in WS-BPEL

Web service composition refers to the creation of new (Web) services by combination of functionality provided by existing ones. This paradigm has gained significant attention in the Web services community and is seen as a pillar for building service-oriented applications. A number of domain-specific languages for service composition have been proposed with consensus being formed around a process-oriented language known as WS-BPEL (or BPEL). The kernel of BPEL consists of simple communication primitives that may be combined using control-flow constructs expressing sequence, branching, parallelism, synchronisation, etc. As a result, BPEL process definitions lend themselves to static flow-based analysis techniques. In this report, we describe a tool that performs two useful types of static checks and extracts meta-data to optimise dynamic resource management. The tool operates by translating BPEL processes into Petri nets and exploiting existing Petri net analysis techniques. It relies on a comprehensive and rigorously defined mapping of BPEL constructs into Petri net structures

Data-Flow Based Model Analysis

The concept of (meta) modeling combines an intuitive way of formalizing the structure of an application domain with a high expressiveness that makes it suitable for a wide variety of use cases and has therefore become an integral part of many areas in computer science. While the definition of modeling languages through the use of meta models, e.g. in Unified Modeling Language (UML), is a well-understood process, their validation and the extraction of behavioral information is still a challenge. In this paper we present a novel approach for dynamic model analysis along with several fields of application. Examining the propagation of information along the edges and nodes of the model graph allows to extend and simplify the definition of semantic constraints in comparison to the capabilities offered by e.g. the Object Constraint Language. Performing a flow-based analysis also enables the simulation of dynamic behavior, thus providing an "abstract interpretation"-like analysis method for the modeling domain

On Dead Path Elimination in Decentralized Process Executions

There has been a great deal of interest in recent years in the use of service oriented approach and relevant standards to implement business processes. Following the concepts of workflow-based process management, the major focus has been on service composition. Not surprisingly, this default composition approach suffers from the limitations of centralized workflow management. It is well recognized that a decentralized execution setting where composed services can establish P2P interactions, is central to a wide range of ubiquitous, mobile, large-scale and secure business process management. A natural way to enable the decentralized execution is to implement the relevant distributed cooperating processes of a centralized process on composed services. In this way, composed services can establish P2P interactions following the semantics of their processes. In this report, we present a generic approach that enables decentralized executions with such cooperating processes. Precisely, we present our method that derives the latter. We focus on the sophisticated control/data flow, conversationional aspects and especially Dead Path Elimination that run counter to naive intuition, most of which, we explain using deeper analysis of the algorithms and data structures that we employed

A transformation-based approach to business process management in the cloud

Business Process Management (BPM) has gained a lot of popularity in the last two decades, since it allows organizations to manage and optimize their business processes. However, purchasing a BPM system can be an expensive investment for a company, since not only the software itself needs to be purchased, but also hardware is required on which the process engine should run, and personnel need to be hired or allocated for setting up and maintaining the hardware and the software. Cloud computing gives its users the opportunity of using computing resources in a pay-per-use manner, and perceiving these resources as unlimited. Therefore, the application of cloud computing technologies to BPM can be extremely beneficial specially for small and middle-size companies. Nevertheless, the fear of losing or exposing sensitive data by placing these data in the cloud is one of the biggest obstacles to the deployment of cloud-based solutions in organizations nowadays. In this paper we introduce a transformation-based approach that allows companies to control the parts of their business processes that should be allocated to their own premises and to the cloud, to avoid unwanted exposure of confidential data and to profit from the high performance of cloud environments. In our approach, the user annotates activities and data that should be placed in the cloud or on-premise, and an automated transformation generates the process fragments for cloud and on-premise deployment. The paper discusses the challenges of developing the transformation and presents a case study that demonstrates the applicability of the approach

An Integrated Methodology for Creating Composed Web/Grid Services

This thesis presents an approach to design, specify, validate, verify, implement, and evaluate composed web/grid services. Web and grid services can be composed to create new services with complex behaviours. The BPEL (Business Process Execution Language) standard was created to enable the orchestration of web services, but there have also been investigation of its use for grid services. BPEL specifies the implementation of service composition but has no formal semantics; implementations are in practice checked by testing. Formal methods are used in general to define an abstract model of system behaviour that allows simulation and reasoning about properties. The approach can detect and reduce potentially costly errors at design time. CRESS (Communication Representation Employing Systematic Specification) is a domainindependent, graphical, abstract notation, and integrated toolset for developing composite web service. The original version of CRESS had automated support for formal specification in LOTOS (Language Of Temporal Ordering Specification), executing formal validation with MUSTARD (Multiple-Use Scenario Testing and Refusal Description), and implementing in BPEL4WS as the early version of BPEL standard. This thesis work has extended CRESS and its integrated tools to design, specify, validate, verify, implement, and evaluate composed web/grid services. The work has extended the CRESS notation to support a wider range of service compositions, and has applied it to grid services as a new domain. The thesis presents two new tools, CLOVE (CRESS Language-Oriented Verification Environment) and MINT (MUSTARD Interpreter), to respectively support formal verification and implementation testing. New work has also extended CRESS to automate implementation of composed services using the more recent BPEL standard WS-BPEL 2.0