Publications in 2007

Articles in Refereed Journals:

1. L. Baresi, D. Bianculli, C. Ghezzi, S. Guinea, P. Spoletini. Validation of web service compositions. IET Software, Vol. 1, Num. 6, pages 219-232, December 2007.
   Abstract: Web services support software architectures that can evolve dynamically. In particular, in this paper the focus is on architectures where services are composed (orchestrated) through a workflow described in the business process execution language (BPEL). It is assumed that the resulting composite service refers to external services through assertions that specify their expected functional and non-functional properties. On the basis of these assertions, the composite service may be verified at design time by checking that it ensures certain relevant properties. Because of the dynamic nature of web services and the multiple stakeholders involved in their provision, however, the external services may evolve dynamically, and even unexpectedly. They may become inconsistent with respect to the assertions against which the workflow was verified during development. As a consequence, validation of the composition must extend to run time. In this work, an assertion language, called assertion language for BPEL process interactions (ALBERT), is introduced; it can be used to specify both functional and non-functional properties. An environment which supports design-time verification of ALBERT assertions for BPEL workflows via model checking is also described. At run time, the assertions can be turned into checks that a software monitor performs on the composite system to verify that it continues to guarantee its required properties. A TeleAssistance application is provided as a running example to illustrate our validation framework.

2. Michael P. Papazoglou, Paolo Traverso, Schahram Dustdar, Frank Leymann. Service-Oriented Computing: State of the Art and Research Challenges. IEEE Computer, To Appear, November 2007.
   Abstract: Service-oriented computing promotes the idea of assembling application components into a network of services that can be loosely coupled to create flexible, dynamic business processes and agile applications that span organizations and computing platforms. An SOC research road map provides a context for exploring ongoing research activities.

3. Ardagna, D., Pernici, B.. Adaptive Service Composition in Flexible Processes. Software Engineering, IEEE Transactions on, Vol. 33, Num. 6, pages 369-384, June 2007.
   Abstract: In advanced service oriented systems, complex applications, described as abstract business processes, can be executed by invoking a number of available Web services. End users can specify different preferences and constraints and service selection can be performed dynamically identifying the best set of services available at runtime. In this paper, we introduce a new modeling approach to the Web service selection problem that is particularly effective for large processes and when QoS constraints are severe. In the model, the Web service selection problem is formalized as a mixed integer linear programming problem, loops peeling is adopted in the optimization, and constraints posed by stateful Web services are considered. Moreover, negotiation techniques are exploited to identify a feasible solution of the problem, if one does not exist. Experimental results compare our method with other solutions proposed in the literature and demonstrate the effectiveness of our approach toward the identification of an optimal solution to the QoS constrained Web service selection problem

4. Bianculli, D., Ghezzi, C., Spoletini, P.. A Model Checking Approach to Verify BPEL4WS Workflows. Service-Oriented Computing and Applications, 2007. SOCA '07. IEEE International Conference on, To Appear, June 2007.
   Abstract: The increasing diffusion of service oriented computing in critical business transactions demands reliability and correctness of the workflow logic representing web service orchestrations. We present an approach for the formal verification of workflow-based compositions of web services, described in BPEL4WS. Workflow processes can be verified in isolation, assuming that the external services invoked are known only through their interface. It is also possible to verify that the actual composition of two or more processes behaves correctly. We can verify deadlock freedom, properties expressed as data-bound assertions written in WS-CoL, a specification language for web services, and LTL temporal properties. Our approach is based on the software model checker Bogor, whose language supports the modeling of all BPEL4WS constructs. We provide an empirical evaluation of our approach and we compare the results with other BPEL4WS model checking tools.

5. Chun Ouyanga, Eric Verbeekb, Wil M.P. van der Aalst, Stephan Breutel, Marlon Dumas, Arthur H.M. ter Hofstede. Formal semantics and analysis of control flow in WS-BPEL. Science of Computer Programming, Vol. 67, Num. 2-3, pages 162-198, April 2007.
   Abstract: 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.

6. Roberto Lucchi, Manuel Mazzara. A pi-calculus based semantics for WS-BPEL . Journal of Logic and Algebraic Programming, Vol. 70, Num. 1, pages 96-118, January 2007.
   Abstract: Recently, the term Web services orchestration has been introduced to address some issues related to Web services composition, that is the way of defining a complex service out of simpler ones. Several proposals for describing orchestration for business processes have been presented in the last years and many of these languages make use of concepts as long-running transactions and compensations for coping with error handling. WS-BPEL 2.0, the most credited candidate for becoming a standard, provides three different mechanisms allowing to cope with abnormal situations: exception, event and compensation handling. This complexity makes it difficult to formally define the framework, thus limiting the formal reasoning about the designed applications. In this paper we advocate that three different mechanisms for error handling are not necessary and we formalize a novel orchestration language based on the idea of event notification as the unique error handling mechanism. To this end, we formally define the three BPEL mechanisms in terms of our calculus. It is possible to take advantages of this formal description in two ways. Firstly, this language represents by itself a proposal of simplification for WS-BPEL 2.0 including an unambiguous specification. Secondly, an implementor of an actual WS-BPEL 2.0 orchestration engine could implement simply this single mechanism providing all the remaining ones by compilation. With this attempt we intend to give a concrete contribute towards the improvement of the quality of the BPEL specification, the applicability of BPEL itself and the implementation of real orchestration engines. Finally, as a case study we consider some of the hundreds of open issues met by the WS-BPEL designers and we propose a solution making use of the experience gained developing our algebra.

7. D. Ardagna, M. Comuzzi, E. Mussi, B. Pernici, P. Plebani. PAWS: A Framework for Executing Adaptive Web-Service Processes. IEEE Software, To Appear, 2007.
   Abstract: The processes with adaptive Web services framework couples design-time and runtime mechanisms to flexibly and adoptively execute managed Web-services-based business processes.

8. Stefano Bistarelli, Ugo Montanari, Francesca Rossi, Francesco Santini. Unicast and Multicast Qos Routing with Soft Constraint Logic Programming. CoRR, Vol. abs/0704.1783, 2007.
   Abstract: We present a formal model to represent and solve the unicast/multicast routing problem in networks with Quality of Service (QoS) requirements. To attain this, first we translate the network adapting it to a weighted graph (unicast) or and-or graph (multicast), where the weight on a connector corresponds to the multidimensional cost of sending a packet on the related network link: each component of the weights vector represents a different QoS metric value (e.g. bandwidth, cost, delay, packet loss). The second step consists in writing this graph as a program in Soft Constraint Logic Programming (SCLP): the engine of this framework is then able to find the best paths/trees by optimizing their costs and solving the constraints imposed on them (e.g. delay < 40msec), thus finding a solution to QoS routing problems. Moreover, c-semiring structures are a convenient tool to model QoS metrics. At last, we provide an implementation of the framework over scale-free networks and we suggest how the performance can be improved.

9. J. Cardoso. Complexity analysis of BPEL Web processes. Software Process: Improvement and Practice, Vol. 12, Num. 1, pages 35-49, Whiley-Interscience, 2007.
   Abstract: Several organizations have already realized the potential of using WS-BEPL, the Process Execution Language for Web Services, to model the behavior of Web services in business processes. WS-BPEL provides a model for describing simple or complex interactions between business partners. In some cases, WS-BPEL process designs can be highly complex, due, for example, to the vast number of Web services carried out in global markets. High complexity in a process has several undesirable drawbacks; it may result in poor understandability, more errors, defects, and exceptions, leading to processes requiring more time to be developed, tested, and maintained. Therefore, excessive complexity should be avoided. Processes that are highly complex tend be less flexible, since it is more complicated to make changes to the process. The major goal of this article is to present two metrics to analyze the control-flow complexity (CFC) of WS-BPEL Web processes. The metrics are to be used at design-time to evaluate the complexity of a process design before implementation actually takes place.

10. Giorgia Lodi, Fabio Panzieri, Davide Rossi, Elisa Turrini. SLA-Driven Clustering of QoS-Aware Application Servers. IEEE Trans. Software Eng., Vol. 33, Num. 3, pages 186-197, 2007.
    Abstract: In this paper, we discuss the design, implementation, and experimental evaluation of a middleware architecture for enabling service level agreement (SLA)-driven clustering of QoS-aware application servers. Our middleware architecture supports application server technologies with dynamic resource management: application servers can dynamically change the amount of clustered resources assigned to hosted applications on-demand so as to meet application-level quality of service (QoS) requirements. These requirements can include timeliness, availability, and high throughput and are specified in SLAs. A prototype of our architecture has been implemented using the open-source J2EE application server JBoss. The evaluation of this prototype shows that our approach makes possible JBoss' resource usage optimization and allows JBoss to effectively meet the QoS requirements of the applications it hosts, i.e., to honor the SLAs of those applications.

11. Fabrizio Montesi, Claudio Guidi, Roberto Lucchi, Gianluigi Zavattaro. JOLIE: a Java Orchestration Language Interpreter Engine. Electr. Notes Theor. Comput. Sci., Vol. 181, pages 19-33, 2007.
    Abstract: Service oriented computing is an emerging paradigm for programming distributed applications based on services. Services are simple software elements that supply their functionalities by exhibiting their interfaces and that can be invoked by exploiting simple communication primitives. The emerging mechanism exploited in service oriented computing for composing services -in order to provide more complex functionalities- is by means of orchestrators. An orchestrator is able to invoke and coordinate other services by exploiting typical workflow patterns such as parallel composition, sequencing and choices. Examples of orchestration languages are XLANG [IBM, "XLANG: Web Services for Business Process Design," http://www.gotdotnet.com/team/xml_wsspecs/xlang-c/default.htm] and WS-BPEL [OASIS, "Web Services Business Process Execution Language Version 2.0, Working Draft," http://www.oasis-open.org/committees/download.php/10347/wsbpel-specification-draft-120204.htm]. In this paper we present JOLIE, an interpreter and engine for orchestration programs. The main novelties of JOLIE are that it provides an easy to use development environment (because it supports a more programmer friendly C/Java-like syntax instead of an XML-based syntax) and it is based on a solid mathematical underlying model (developed in previous works of the authors [N. Busi, R. Gorrieri, C. Guidi, R. Lucchi and G. Zavattaro, Towards a formal framework for Choreography, in: Proc. of 3rd International Workshop on Distributed and Mobile Collaboration (DMC 2005) (2005), N. Busi, R. Gorrieri, C. Guidi, R. Lucchi and G. Zavattaro, Choreography and orchestration conformance for system design, in: Proc. of 8th International Conference on Coordination Models and Languages (COORDINATION'06), LNCS to appear, 2006, C. Guidi and R. Lucchi, Mobility mechanisms in service oriented computing, in: Proc. of 8th International Conference on on Formal Methods for Open Object-Based Distributed Systems (FMOODS'06), LNCS to appear, 2006]).

12. Mike P. Papazoglou, Benedikt Kratz. Web services technology in support of business transactions. Service Oriented Computing and Applications, Vol. 1, Num. 1, pages 51-63, 2007.
    Abstract: Advanced business applications typically involve well-defined business functions such as payment processing, shipping and tracking, determining new product offerings, granting/extending credit, managing market risk and so on. These reflect commonly standard business functions that apply to a variety of application scenarios. Although such business functions drive transactional applications between trading partners they are completely external to current Web services transaction mechanisms and are only expressed as part of application logic. To remedy this situation, this paper proposes a business-aware Web services transaction model and support mechanisms, which is driven by common business functions. The model allows expressing business functions such as payment and credit conditions, delivery conditions, business agreements stipulated in SLAs, liabilities and dispute resolution policies. It allows blending these business functions with QoS criteria such as security support to guarantee integrity of information, confidentiality, and non-repudiation.

Articles in Refereed Conferences:

1. Kyriakos Kritikos, Dimitris Plexousakis. OWL-Q for Semantic QoS-based Web Service Description and Discovery. First International Joint Workshop on Service Matchmaking and Resource Retrieval in the Semantic Web, November 2007.
   Abstract: Semantic Web Services are emerging for their promise to produce a more accurate and precise Web Service discovery process. However, most of research approaches focus only on the functional part of semantic Web Service description. The above fact along with the proliferation of Web Services is highly probable to lead to a situation where Web Service registries will return many functionally-equivalent Web Service advertisements for each user request. This problem can be solved with the semantic description of QoS for Web Services. QoS is a set of non-functional properties encompassing performance and network- related characteristics of resources. So it can be used for distinguishing between functionally-equivalent Web Services. Current research approaches for QoS-based Web Service description are either syntactic or poor or non-extensible. To solve this problem, we have developed a rich and extensible ontological specification called OWL-Q for semantic QoS-based Web Service description. We analyze all OWL-Q parts and reason that rules should be added in order to support property inferencing and constraint enforcement. Finally, we line out our under-development semantic framework for QoS-based Web Service description and discovery.

2. Cinzia Cappiello, Marco Comuzzi, Pierluigi Pleban. On Automated Generation of Web Service Level Agreements . Advanced Information Systems Engineering, Vol. 4495, Springer Verlag, June 2007.
   Abstract: Before a service invocation takes place, an agreement between the service provider and the service user might be required. Such an agreement is the result of a negotiation process between the two parties and defines how the service invocation has to occur. Considering the Service Oriented Computing paradigm, the relationship among providers and users is extremely loose. Traditional agreements are likely to concern long term relationships and to be manually performed. In this paper, we propose a model to generate service level agreement on-the-fly. Just before the invocation commences, the quality of the service is negotiated in order to generate a service level agreement tied to that specific invocation. Such an approach relies on a quality model that supports both users requirements and providers capabilities definition.

3. Jonatha Anselmi, Danilo Ardagna, Paolo Cremonesi. A QoS-based selection approach of autonomic grid services. SOCP '07: Proceedings of the 2007 workshop on Service-oriented computing performance: aspects, issues, and approaches, pages 1-8, ACM, 2007.
   Abstract: The Web service composition (WSC) is the process of building an instance of an abstract workflow by combining appropriate Web services that satisfies given QoS requirements. In general, QoS requirements consists of a number of constraints. The selection process requires global optimization and can be formalized as a mixed integer linear programming problem which cannot be solved in polynomial time. However, since the number of submitted workflows is large and the QoS is highly dynamic, the fast selection of composite Web Services is particularly important. In this paper, we present a QoS broker-based framework for Web services execution in autonomic grid environments. The main goal of the framework is to support the broker in selecting Web services based on the required QoS. To achieve this goal, we propose a novel approach: since successive composed Web services requests can have the same task to Web service assignment, we address the Multiple Instance WSC (MI-WSC) problem optimizing simultaneously the set of requests which will be submitted to the system in the successive time interval instead of independently computing a solution for each incoming request. Experimental results show that the proposed algorithm has better performance with respect to existing techniques. Moreover, the qualities of the selected composite Web services are not significantly different from the optimal ones.

4. Gero Decker, Oliver Kopp, Frank Leymann, Mathias Weske. BPEL4Chor: Extending BPEL for Modeling Choreographies. ICWS, pages 296-303, 2007.
   Abstract: The Business Process Execution Language (BPEL) is a language to orchestrate web services into a single business process. In a choreography view, several processes are interconnected and their interaction behavior is described from a global perspective. This paper shows how BPEL can be extended for defining choreographies. The proposed extensions (BPEL4Chor) distinguish between three aspects: (i) participant behavior descriptions, i.e. control flow dependencies in each participant, (ii) the participant topology, i.e. the existing participants and their interconnection using message links and (iii) participant groundings, i.e. concrete configurations for data formats and port types. As BPEL itself is used unchanged, the extensions facilitate a seamless integration between service choreographies and orchestrations. The suitability of the extensions is validated by assessing their support for the Service Interaction Patterns.

5. Ester Giallonardo, Eugenio Zimeo. More Semantics in QoS Matching. SOCA, pages 163-171, 2007.
   Abstract: The evolution of the Web towards a global computing environment is promoting new research efforts aimed at the formal characterization of Web Services QoS. Reasoning on QoS is a key to improve matching process during the discovery of desired services and a step towards the transformation of applications in collections of loosely coupled services virtually connected by semantic similarities. The paper presents the on QoS ontology, an openly available OWL ontology for QoS, and evaluates it in a QoS-aware matching environment. The ontology can be used to express functions of QoS metrics useful to improve the recall tied to the matching of a template request with target Web Services. To this end, the ontology introduces the concept of derivation in the matching process. This gives the possibility of matching a QoS template with published Web Services by deriving different QoS parameters when a one-to-one matching fails. The proposed matching algorithm utilizes a reasoner that exploits the ontology to avoid apparent mismatches. An experimental evaluation shows that exploiting QoS knowledge significantly improves matching recall without deteriorating precision.

6. Dimka Karastoyanova, Branimir Wetzstein, Tammo van Lessen, Daniel Wutke, Jörg Nitzsche, Frank Leymann. Semantic Service Bus: Architecture and Implementation of a Next Generation Middleware. ICDE Workshops, pages 347-354, 2007.
   Abstract: In this paper we present a middleware for the service oriented architecture, called the Semantic Service Bus. It is an advanced middleware possessing enhanced features, as compared to the conventional service buses. It is distinguished by the fact that it uses semantic description of service capabilities, and requirements towards services to enable more elaborate service discovery, selection, routing, composition and data mediation. The contributions of the paper are the conceptual architecture of the Semantic Service Bus and a prototypical implementation supporting different semantic Web service technologies (OWL-S and WSMO) and conventional Web services. Since mission critical application scenarios (for SOA) involve complex orchestrations of services, we have chosen to utilize semantically annotated service orchestrations as the applications to employ this middleware.

7. Kyriakos Kritikos, Dimitris Plexousakis. Requirements for QoS-based Web Service Description and Discovery. COMPSAC (2), pages 467-472, 2007.
   Abstract: The goal of Service Oriented Architectures is to enable the creation of business applications through the automatic discovery and composition of independently developed and deployed (Web) services. Automatic discovery of Web Services (WSs) can be achieved by incorporating semantics into a richer WS description model (WSDM) and the use of Semantic Web (SW) technologies in the WS matchmaking and selection models. A sufficiently rich WSDM should encompass not only functional but also non-functional aspects like Quality of Service (QoS). QoS is a set of performance attributes that has a substantial impact on WS requesters' expectations. Thus, it can be used as a discriminating factor of functionally-equivalent WSs. The focus of this paper is twofold: to analyze the requirements of a semantically rich QoS-based WSDM and to provide SW and constrainedbased mechanisms for enriching syntactic QoS-based WS Discovery (WSDi) algorithms. In addition, a roadmap of extending WS standard techniques for realizing semantic, functional and QoS-based WSDi is presented.

8. Kyriakos Kritikos, Dimitris Plexousakis. Semantic QoS-based Web Service Discovery Algorithms. Fifth European Conference on Web Services, pages 181-190, IEEE Computer Society, 2007.
   Abstract: The success of the Web Service (WS) paradigm has led to a proliferation of available WSs, which are advertised in WS registries. While sophisticated semantic WS discovery algorithms are operating on these registries to return matchmaking results with high precision and recall, many functionally-equivalent WSs are returned. The solution to the above problem comes in terms of semantic QoS-based description and discovery of WSs. We have already presented a rich and extensible ontology language for QoS-based WS description called OWL-Q. We have also proposed a semantic QoS metric matching algorithm. Based on this algorithm, we have extended a CSP-based approach for QoS-based WS discovery. In this paper, we firstly analyze the evolution of OWL-Q and its extension with SWRL rules, we propose a modification to the metric matching algorithm and we show the way the metric alignment process takes place. Then we propose two novel semantic QoS-based WS Discovery algorithms that return matches even for over-constrained QoS-based WS requests. The first one deals with unary constraints while the second one is more generic. Finally, implementation aspects of our QoS-based WS discovery system are discussed.

9. Anca Muscholl, Igor Walukiewicz. A Lower Bound on Web Services Composition. FoSSaCS, pages 274-286, 2007.
   Abstract: A web service is modeled here as a finite state machine. A composition problem for web services is to decide if a given web service can be constructed from a given set of web services; where the construction is understood as a simulation of the specification by a fully asynchronous product of the given services. We show an EXPTIME-lower bound for this problem, thus matching the known upper bound. Our result also applies to richer models of web services, such as the Roman model.

10. Elisabetta Di Nitto, Massimiliano Di Penta, Alessio Gambi, Gianluca Ripa, Maria Luisa Villani. Negotiation of Service Level Agreements: An Architecture and a Search-Based Approach. ICSOC, pages 295-306, 2007.
    Abstract: Software systems built by composing existing services are more and more capturing the interest of researchers and practitioners. The envisaged long term scenario is that services, offered by some competing providers, are chosen by some consumers and used for their own purpose, possibly, in conjunction with other services. In the case the consumer is not anymore satisfied by the performance of some service, he can try to replace it with some other service. This implies the creation of a global market of services and poses new requirements concerning validation of exploited services, security of transactions engaged with services, trustworthiness, creation and negotiation of Service Level Agreements with these services. In this paper we focus on the last aspect and present our approach for negotiation of Service Level Agreements. Our architecture supports the actuation of various negotiation processes and offers a search-based algorithm to assist the negotiating parts in the achievement of an agreement.

11. Qing Zhu, Shan Wang, Guorong Li, Guangqiang Liu, Xiaoyong Du. QoS-Based Services Selecting and Optimizing Algorithms on Grid. APWeb/WAIM Workshops, pages 156-167, 2007.
    Abstract: QoS-Based Services Selecting and Optimizing Composition between the peers play an increasingly important role to ensure interoperability on Grid environment. However, the prohibitive cost of selecting, matching, mapping and composing algorithm has now become a key bottleneck hindering the deployment of a wide variety of Grid services. In this paper, we present QoS-Based Services Selecting and Optimizing Composition on Grid. First, it checks requesters' semantic in order to form candidate service graph. Second, it designs service selecting and mapping algorithms for optimizing the model. Third, it creates an executed plan of optimum composition on Grid. We conducted experiments to simulate and evaluate our approach.

Articles in Books and Other Collections:

1. Natasha Sharygina, Daniel Kröning. Model Checking with Abstraction for Web Services. Test and Analysis of Web Services, pages 121-145, 2007.
   Abstract: Web services are highly distributed programs and, thus, are prone to concurrency-related errors. Model checking is a powerful technique to identify flaws in concurrent systems. However, the existing model checkers have only very limited support for the programming languages and communication mechanisms used by typical implementations of web services. This chapter presents a formalization of communication semantics geared for web services, and an automated way to extract formal models from programs implementing web services for automatic formal analysis. The formal models are analyzed by means of a symbolic model checker that implements automatic abstraction refinement. Our implementation takes one or more PHP5 programs as input, and is able to verify joint properties of these programs running concurrently.

Technical Reports and Manuals:

1. Oliver Kopp, Rania Khalaf, Frank Leymann. Reaching Definitions Analysis Respecting Dead Path Elimination Semantics in BPEL Processes. Num. 2007/04, Institut für Architektur von Anwendungssystemen, November 2007.
   Abstract: The Business Process Execution Language for Web Services (BPEL) is a workflow language geared towards Service Oriented Computing. BPEL provides basic workflow capabilities, such as the ability to impose control on a set of activities via explicit links, as well as advanced features such as recovery and event handling. The area of workflow often requires understanding the data dependencies as well as the control dependencies between activities. This aids in business process design as well as in analysis and rengineering. BPEL, however, uses shared variables to model data. Activities read and write data to these variables, i.e. there is no explicit data link construct. In order to draw out the flow of data between the activities of a BPEL process, one must therefore perform data-flow analysis on that process. To address this problem, we present an algorithm that statically determines such data dependencies. "Statically" means, that we do not determine the dependencies per process instance at runtime, but on the process model without creating any instances. Mainstream data-flow analysis techniques are presented in [ALSU06, Muc97, NNH04]. However, these techniques cannot be directly applied to a BPEL process, since BPEL supports both parallelism and dead path elimination (DPE, [CDG+ 03, OAS07, CKLW03, BK05, LR00]). DPE is a technique used in BPEL to propagate activity disablement down paths that can no longer be executed. The algorithm in this paper consists of reaching definitions analysis dealing with DPE, enabling it to reduce the number of data dependencies when compared to approaches not dealing with DPE.

2. Diane Jordan, John Evdemon, Alexandre Alves, Assaf Arkin, Sid Askary, Charlton Barreto, Ben Bloch, Francisco Curbera, Mark Ford, Yaron Goland, Alejandro Guízar, Neelakantan Kartha, Canyang Kevin Liu, Rania Khalaf, Dieter König, Mike Marin, Vinkesh Mehta, Satish Thatte, Danny van der Rijn, Prasad Yendluri, Alex Yiu . Web Services Business Process Execution Language Version 2.0. IBM, Microsoft, BEA, Intalio, Individual, Adobe Systems, Systinet, Active Endpoints, JBoss, Sterling Commerce, SAP, Deloitte, TIBCO Software, webMethods, Oracle, 2007.
   Abstract: This document defines a language for specifying business process behavior based on Web Services. This language is called Web Services Business Process Execution Language (abbreviated to WS-BPEL in the rest of this document). Processes in WS-BPEL export and import functionality by using Web Service interfaces exclusively. Business processes can be described in two ways. Executable business processes model actual behavior of a participant in a business interaction. Abstract business processes are partially specified processes that are not intended to be executed. An Abstract Process may hide some of the required concrete operational details. Abstract Processes serve a descriptive role, with more than one possible use case, including observable behavior and process template. WS-BPEL is meant to be used to model the behavior of both Executable and Abstract Processes. WS-BPEL provides a language for the specification of Executable and Abstract business processes. By doing so, it extends the Web Services interaction model and enables it to support business transactions. WS-BPEL defines an interoperable integration model that should facilitate the expansion of automated process integration in both the intra-corporate and the business-to- business spaces.