Service Composition Language Research Articles

Guest Editors' Introduction on eHealth and Services Computing in Healthcare

is often perceived to lag behind other industry sectors in its uptake and adoption of new technology. eHealth is one such technology which includes the areas of Health Informatics, Electronic Medical/Patient Records, Clinical Decision Support, Telehealth. The main purpose of eHealth is to provide better use of information in health care settings, to improve the quality of patient care and the efficiency of clinical processes. Many situations exist where the use of eCommerce principles would be appropriate to establish new eHealth solutions, and these warrant extensive research investigation. Computing has been described as a cross-discipline that covers the science and technology of bridging the gap between Business and IT Services (Site 1). This role is supported by Web services and service-oriented architecture (SOA), business consulting methodology and utilities, business process modelling, transformation and integration. The goal of Computing is to enable IT services and computing technology to perform business services more efficiently and effectively. Opportunities abound for the unique aspects of healthcare to drive fundamental computing and IT research together with leading applied research within the healthcare domain that could potentially be reapplied to areas outside of healthcare. This special issue contains articles addressing eHealth and Computing in from several different perspectives. The first three articles set the scene for research within this domain by focusing on business process modelling within healthcare and e-health, otherwise known as patient flow or patient journey modelling. While many healthcare organisations are utilising Lean Thinking (Site 2) based approaches, these research articles show that improvements can be made to these initiatives through approaches that better support the nuances of healthcare when compared to the retail and manufacturing sectors for example. The first paper entitled An Evaluation Framework for Business Process Modelling Languages in Healthcare coauthored by Amir Afrasiabi Rad, Morad Benyoucef and Craig E. Kuziemsky sets the scene by introducing the healthcare domain, the business processes within it; healthcare's modeling requirements, and challenges of healthcare business process modeling. With this in mind they present the difficulties of modeling complex healthcare processes in a service based environment. They present a set of healthcare modeling requirements and propose an evaluation framework for process modeling languages based on these requirements. This is demonstrated through the evaluation of the suitability of two major process based service composition languages supporting services computing, namely BPEL and WS-CDL. The second paper entitled Using Visual Analytics to Improve Hospital Scheduling and Patient Flow co-authored by Janna Anneke Fitzgerald and Ann Dadich presents an innovative approach to extend the lean thinking approach premised on visual analytics. They demonstrate that this approach can identify areas for improvement without having to make changes to the physical environment through a visual communication mechanism with staff. …

An Evaluation Framework for Business Process Modeling Languages in Healthcare

Web services composition is an emerging paradigm for enabling inter and intra organizational integration, and a landscape of languages and techniques for modeling business processes in web service based environments has emerged and is continuously being enriched. With the advent of modeling standards, different business sectors are investigating the options for modeling their workflows. In terms of business process modeling, healthcare is a rather complex sector of activity. Indeed, modeling healthcare processes presents special requirements dictated by the complicated and dynamic nature of these processes as well as by the specificity and diversity of the actors involved in these processes. Little effort has been dedicated to evaluating the capabilities and limitations of modeling languages based on healthcare requirements. This paper presents a set of healthcare modeling requirements and proposes an evaluation framework for process modeling languages based on these requirements. The suitability of two major process based service composition languages, namely BPEL and WS-CDL, is evaluated.

COMPOSING SERVICES INTO STRUCTURED PROCESSES

Service composition languages like BPEL and many enactment tools only support structured process models, but most service composition approaches only consider unstructured process models. This paper defines an efficient algorithm that composes a set of cooperative services with their dependencies into a structured process. The algorithm takes as input a dependency graph and returns a structured process model that orchestrates the services while respecting their dependencies. The algorithm is embedded in a lightweight, semi-automated service composition approach, in which first dependencies between services are derived in a semi-automated way and next the algorithm is used to construct a structured composition. The approach has been implemented in a prototype that supports the dynamic formation and collaboration of dynamic virtual enterprises using cross-organizational service-oriented technology.

RESTful Web service composition with BPEL for REST

Current Web service technology is evolving towards a simpler approach to define Web service APIs that challenges the assumptions made by existing languages for Web service composition. RESTful Web services introduce a new kind of abstraction, the resource, which does not fit well with the message-oriented paradigm of the Web service description language (WSDL). RESTful Web services are thus hard to compose using the Business Process Execution Language (WS-BPEL), due to its tight coupling to WSDL. The goal of the BPEL for REST extensions presented in this paper is twofold. First, we aim to enable the composition of both RESTful Web services and traditional Web services from within the same process-oriented service composition language. Second, we show how to publish a BPEL process as a RESTful Web service, by exposing selected parts of its execution state using the REST interaction primitives. We include a detailed example on how BPEL for REST can be applied to orchestrate a RESTful e-Commerce scenario and discuss how the proposed extensions affect the architecture of a process execution engine.

Composing software services in the pervasive computing environment: Languages or APIs?

The pervasive computing environment will be composed of heterogeneous services. In this work, we have explored how a domain specific language for service composition can be implemented to capture the common design patterns for service composition, yet still retain a comparable performance to other systems written in mainstream languages such as Java. In particular, we have proposed the use of the method delegation design pattern, the resolution of service bindings through the use of dynamically adjustable characteristics and the late binding of services as key features in simplifying the service composition task. These are realised through the Scooby language, and the approach is compared to the use of APIs to define adaptable services.

Formal semantics and analysis of control flow in WS-BPEL

Web service composition refers to the creation of new (Web) services by combining functionalities provided by existing ones. 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, synchronization, etc. We present a comprehensive and rigorously defined mapping of BPEL constructs onto Petri net structures, and use this for the analysis of various dynamic properties related to unreachable activities, conflicting messages, garbage collection, conformance checking, and deadlocks and lifelocks in interaction processes. We use a mapping onto Petri nets because this allows us to use existing theoretical results and analysis tools. Unlike approaches based on finite state machines, we do not need to construct the state space, and can use structural analysis (e.g., transition invariants) instead. We have implemented a tool that translates BPEL processes into Petri nets and then applies Petri-net-based analysis techniques. This tool has been tested on different examples, and has been used to answer a variety of questions.

Applying Triple Graph Grammars For Pattern-Based Workflow Model Transformations.

Workflow and business process modeling approaches have become essential for designing service collaborations when developing SOA-based systems. To derive actual executable business process descriptions from the high-level workflow models, model transformation techniques can be used. Various service composition and business process languages are available for describing the executable processes. They have been developed having slightly different aims and requirements in mind. They do, however, share common key constructs, called workflow patterns that recur in descriptions given in these languages. We propose a model-driven approach for transforming workflow models given as UML activity diagrams into service composition descriptions. This paper will show how to realize a transformation from UML to BPEL and XPDL with a technology based on Triple Graph Grammars (TGGs). TGGs allow structural relationships between the different model elements to be elegantly expressed in graphical, declarative rules. We will show, in particular, how the commonly known workflow patterns recurring in the different business process languages can act as a guideline for designing the transformation rules. Based on the experiences in this application domain, we furthermore outline ways to enhance the usability and applicability of TGG for this purpose.

Interface theory-based formalisation and verification of orchestration in BPEL4WS

BPEL4WS (BPEL) is a web service composition language for service-oriented computing. Service orchestration can be specified by executable processes in BPEL. However, it lacks of a formal foundation for specification and verification of service-oriented systems. This paper presents an improved protocol interface for web services. Compared to the existing interface theory, the presented interface can describe some more advanced features of long running transaction such as nested transaction. An interface theory-based formalisation is presented for service orchestration in BPEL. The transformational approach is proposed for translating BPEL processes to protocol interfaces. With the formalisation, a formal technique is presented for model checking of BPEL program with respect to the protocol properties. A set of case studies are demonstrated to illustrate our approach.

Theoretical foundations for compensations in flow composition languages

A key aspect when aggregating business processes and web services is to assure transactional properties of process executions. Since transactions in this context may require long periods of time to complete, traditional mechanisms for guaranteeing atomicity are not always appropriate. Generally the concept of long running transactions relies on a weaker notion of atomicity based on compensations. For this reason, programming languages for service composition cannot leave out two key aspects: compensations , i.e. ad hoc activities that can undo the effects of a process that fails to complete, and transactional boundaries to delimit the scope of a transactional flow. This paper presents a hierarchy of transactional calculi with increasing expressiveness. We start from a very small language in which activities can only be composed sequentially. Then, we progressively introduce parallel composition, nesting, programmable compensations and exception handling. A running example illustrates the main features of each calculus in the hierarchy.

Modelling web service composition with UML 2.0

Web services and web service composition languages for web service choreography are becoming more and more important in the area of inter-enterprise integration. A huge amount of work has been done in the area of web service composition languages. However, the aspects of modelling these specific kinds of software systems have not been studied in detail, in contrast to the definition of business processes where a lot of well-known techniques exist. In this paper, we show how the usage of UML 2.0 and agent specific extensions of it can contribute to the specification of web service choreography. We will start by introducing the notion of web services and web service compositions languages. Then we show how business processes can be specified using UML 2.0 in general by a small case study. Next these business processes are refined to the level of negotiation and processes between web services.

An XSLT Based Framework for Automating Peer-To-Peer Interactions between Complex Business Processes

New developments in service-oriented computing allow the creation of Web services-enabled business processes that can be defined through the composition of a set of existing services. Recently many proposals have emerged along this line, including BPSS, BPML, and BPEL4WS, with little effort spent on the development of systematic methods to effectively support composition of partner business processes that dynamically discover and interact with publicly available business processes at runtime. Motivated by this, this paper proposes a framework for automatically synthesizing the partner business processes, named Co-BP, from the formal description of a target business process, and discusses preliminary work on implementing the proposed ideas by use of XSLT. The proposed framework bases its foundation on the well-known Petri net techniques such as reachability analysis and theory of regions. It is expected that the work presented in this paper can promote the rapid adoption of Web services composition languages by providing an automated tool for facilitating seamless integration of distributed business processes.