WSMX is an execution environment aiming to enable fully automated discovery, ... and process heterogeneity reconciliation in B2B integration is presented.
Semantic Web Services as Foundation for Enterprise Interoperability Srdjan Komazec, Omair Shafiq, Federico Facca, Michal Zaremba, Mick Kerrigan STI Innsbruck, Technikerstrasse 21a, 6020 Innsbruck, Austria, {firstname.lastname}@sti2.at Abstract This paper presents an overview of the Web Service Execution Environment (WSMX) and its basic support for issues originating in the Enterprise Interoperability (EI) problem domain. WSMX is a reference implementation of the Web Service Modeling Ontology (WSMO), which is a conceptual model used to describe various aspects related to Semantic Web Services (SWS). WSMX is an execution environment aiming to enable fully automated discovery, selection, mediation, invocation and interoperation of the SWSs. It is a platform characterized by strong component decoupling and goal-driven Web service usage. Certain components of the platform can directly contribute to the EI requirements identified by current research and technical efforts thus making WSMX suitable as the foundational platform for solving EI issues. To justify this claim a use case representing a WSMX based solution addressing data and process heterogeneity reconciliation in B2B integration is presented. Keywords Semantic Web Services, Enterprise Interoperability, WSMO, WSMX, semantics
1
Introduction
In order to take advantage of the emerging market opportunities driven by the accelerating economy, the way businesses operate is changing rapidly from traditional, centralized and static supply chains towards new, decentralized, flexible and dynamic networked organizational models. This paradigm shift establishes delivery of business functions in the form of services and the dominant approach in employing service orientation is the application of the Service Oriented Architectures (SOA) paradigm. Although well established and recognized as the nextgeneration computing paradigm, SOA has some weaknesses in terms of its adaptivity to business changes. [Vitvar et al. 2007a] state that existing SOA solutions will prove difficult to scale without a proper degree of automation. The introduction of semantics as an extension of SOA and the creation of Semantically Enabled Service Oriented Architectures (SESA) [Fensel et al. 2008] addresses these drawbacks by bringing adaptation, automation, reduction of manualintensive efforts and scalability to the SOA. The Web Service Execution Environment (WSMX) provides an open-source development and execution environment for SESA. It consists of a number of functional components dealing with specific tasks under the Semantic Web Services (SWS) umbrella such as discovery, composition, data and process mediation, choreography, orchestration and invocation of services. Enterprise Interoperability (EI) [Li et al. 2006] is defined as the set of activities aiming to improve the manner in which enterprises, by means of ICT, interoperate in order to conduct their business. The same source states that enterprises need to collaborate in order to reduce costs, raise flexibility, innovate products and gain overall competitive advantages. Such high demands for comprehensive collaboration introduces complex interoperability issues such as seamless communication and integration of data and information as well as synchronized interorganisational business processes. As shown in the Section 3, WSMX can directly contribute to the requirements identified by current EI research efforts thus making it suitable as a foundational platform for solving EI issues.
The rest of the paper is structured as follows: Section 2 gives an overview of the WSMX platform. Section 3 is devoted to the identification of current EI questions, which could be answered by the application of the WSMX. In order to justify the approach, Section 4 brings the overview of the use case that represents a WSMX based solution addressing data and process heterogeneities in the B2B integration. The last section concludes the paper and gives directions for the future research.
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Overview of the WSMX platform
WSMX [Bussler et al. 2005] is an execution environment for SWS, which realizes dynamic discovery, selection, composition, mediation, invocation and execution and monitoring of Web services. It is a platform characterized by strong component decoupling, goal-driven Web service usage and direct support for mediation facilities. WSMX is a reference implementation of the Web Services Modeling Ontology (WSMO) [Fensel et al. 2007] that acts as the conceptual model which describes various aspects of SWS. WSMO is based on four major fundamental elements: Ontologies represent the formal specifications of the knowledge domain used by both Web Service and Goal descriptions, Web services provide a formal description of the functionality provided by the Web service defined in the terms of its capability (describing logically what the service can offer), and interface (specifying how clients should communicate with the service – choreography and how the service integrates functionality of other services orchestration), Goals provide a means for the user to formally describe desired requirements, i.e. what the user wants to achieve, and Mediators are used to solve data, protocol and process level heterogeneity issues, e.g. differences in the ontologies used in description of Web Services and Goals respectively. WSMX can achieve the goal of the user by dynamically discovering and selecting a matching Web service, mediating the data that needs to be communicated to this service and invoking it. The detailed architecture which introduces the abstract software components that build up WSMX is shown in the Figure 1. In order to provide for complete SWS lifecycle support, WSMX platform comprises several components with clear functional responsibilities [Zaremba et al. 2005]: WSMX Manager Core component is the central part of WSMX, managing all other components and interactions between them. The Core is responsible for a number of the tasks such as the business logic of the system, the events engine, the internal workflow engine, and the loading of distributed components, Resource manager offers an interface for WSMX persistent storage facilities. It contracts repository access to four different WSMO concept elements, events exchanged inside the environment, messages used during environment execution and WSDL files used to ground WSMO service descriptions to SOAP or SOAP/HTTP, Discovery component is concerned with finding Web service descriptions that match the goal specified by the service requester. The responsibility of the component is to compare WSMO description of the goal a user wishes to achieve (described in terms of desired capability) to the WSMO description of Web services known to WSMX (described in terms of offered capabilities). The component returns a (possibly empty) list of Web service descriptions, Selector component is used in cases where there is more than one service capable of fulfilling the requester’s goal in order to select the most suitable service based on non-
functional properties like price, guaranteed response time, etc. Selection doesn’t involve making an invocation on the service, Data Mediator component has the role of reconciling the data heterogeneity problems that can appear during discovery, composition, selection or invocation of Web Services. During the run-time phase it retrieves mappings from the storage that have been created in advance during design-time phase, transforms them into rules, and finally executes them against the specified incoming data instances in order to obtain the target data instances. Since the mappings represent the connection point between the two subcomponents (design-time and run-time) one of the dependencies for the run-time component relates to the mapping storage level. Another crucial dependency relates to the reasoning system used for executing the rules in the final stage of the mediation process, Process Mediator component reconciles the process heterogeneity that can appear during the invocation of Web services, i.e. it ensures that the public processes of the invoker and the invoked Web service match. Since since both the invoker and the Web Service publish their public processes as choreographies, and the public processes are executed by sending and receiving messages, the Process Mediator will deal with reconciliation of message exchange patterns based on choreography descriptions, Communication manager component is responsible for dealing with the protocols for sending and receiving messages to and from WSMX. Its external behaviour is accessed through the Invoker and Receiver interfaces. The Invoker is used by WSMX when a Web service needs to be invoked. The Receiver interface accepts the messages expressed in WSML and handles any transport and security protocols used by the message sender and Choreography Component defines the communication patterns in terms of messages exchanged in order to interact with the Web service. The components of the WSMX extensively use parser in order to check if the syntax of received WSML descriptions is correct and to create WSMO4J1 object model that stands for internal data representation of the WSMO elements.
Figure 1 – Detailed architecture of the WSMX
It is envisioned that concrete usage scenarios do not need to employ all WSMX components. For example, sometimes only Web service discovery (including discovery, selection and mediation
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http://wsmo4j.sourceforge.net
components) is desired, without the need to proceed with the actual service invocation. The notion of execution semantics is introduced in order to support the formal specification of the operational behaviour of a concrete WSMX deployment. The execution semantics can be regarded as abstract process definitions governing WSMX’s business activity (i.e. orchestration of various components) undertaken by a core component in pursuit of the defined goal. Different execution semantics are hidden behind WSMX entry points which represent the gateway to access functionality provided by the environment. Accessing WSMX through its entry point means instantiating and enacting assigned execution semantics. WSMX entry points can be published in the form of Web service endpoints, thus making the functionality offered by the platform behave according to SOA principles. While syntactic level messaging (e.g. in the format of XML) is generally used to transmit and process messages over the public infrastructure, internal WSMX operation relies upon semantic representation of data (i.e. data represented in an ontological format). One of the main roles of the Data and Communications Protocols Adapters layer is to translate the goal to its WSML representation (i.e. to lift the goal description to its semantically described counterpart). The Web Services Modelling Toolkit (WSMT) [Kerrigan et al. 2007] is an integrated development environment for Semantic Web Services that enables developers to develop Ontologies, Web Services, Goals and Mediators through the Web Service Modeling Language (WSML) formalism of WSMO. The WSMT is implemented as a collection of plug-ins for the Eclipse2 framework and provides textual as well as graphical means for all WSMO elements. Additionally it integrates a number of reasoners, discovery engines, and data mediation into the design time environment enabling the Semantic Web Service engineer to test their descriptions in the design time environment prior to deploying them to WSMX. It also provides functionality for monitoring and managing instances of the WSMX environment and is especially useful for deploying descriptions to and from a given WSMX instance.
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SWS as a solution for EI Issues
As EI becomes a fundamental necessity that pervades all industries, research efforts in this area are gaining in momentum. [Li et al. 2006] proposed and [Charalabidis et al. 2008] further refined Grand Challenges (GCs) that represent global domains of research in the EI problem domain. The GCs constitute frames which define more concrete and indicative research challenges. In the rest of the section we will match the properties of the envisioned comprehensive EI framework shaped according to the identified research challenges with the current properties of the WSMX platform.
3.1
Interoperability Service Utility
The Interoperability Service Utility (ISU) GC defines interoperability as the utility-like capability that should be used ubiquitously and transparently by enterprises. The ISU envisions delivery of IT functionalities as services based on an end-to-end principle (i.e. Internet design principle). The ISU should leverage its functionality on the suite of open standards and specifications on top of which exchange of information and knowledge meaningful to computers should be implemented. In order to define additional and new capabilities to be built on the top of the ISU it must support transparency. The WSMX platform is capable of addressing all aforementioned properties. It is build around the notion of the service and SOA, thus inheriting all their design principles. The functionality of the platform is adjusted to the set of open standards and specifications (such as WSDL, SOAP, XML, XSLT, etc) but it is not bound to any of them (the internal operational model is based on the semantic representation of the data that could be lowered to arbitrary representations). 2
http://www.eclipse.org
Additionally, the platform functionality heavily leverages ontologies as the prime knowledge representation mechanism shared between other WSMO elements. WSMX can play the role of the integrator between distributed nodes thus transparently adding valuable capabilities (as a result of semantic descriptions and operations such as discovery, selection, mediation, etc).
3.2
Future Internet and Enterprise Systems
The Future Internet and Enterprise Systems GC deals with the application of concepts, technologies and solutions arising from novel approaches on the Internet in the area of EI. The value of the services provided by the enterprise should be enhanced with a higher degree of control in the configuration and delivery of the service. The applications should be able to request remote execution of functions in a distributed architecture. The technologies for automating semantic reconciliation and process flow management among diverse systems and services should also be part of the EI framework. The problems raised by this GC envision heavy usage of semantics and ontologies in many areas (service specifications, remote functions specifications, data and process heterogeneities reconciliations, etc). Semantically rich descriptions of services (and remaining WSMO elements) processed by the WSMX enable dynamic, on-the-fly search and adaptability of services. Furthermore, features like service composition and selection provided by the WSMX directly contribute to the configurability in the delivery of services. Web service capability and interface descriptions (Section 2) can be used during the whole SWS execution. The data and process heterogeneities reconciliation are addressed by the usage of mediators (one of the top-level elements of WSMO).
3.3
Knowledge-Oriented Collaboration and Semantic Interoperability
The Knowledge-Oriented Collaboration and Semantic Interoperability GC builds around the notion of “virtual organization” (VO), which defines a group of legally distinct or related enterprises that are joining in order to exploit a particular product or service opportunity. Such an environment establishes knowledge sharing as the key during the formation, operation and evolvement of the VOs. Some of the distinguishing properties of the EI framework compliant to VO principles should be novel methodologies, techniques and tools for the discovery, capture, representation and reuse of knowledge collaborative capabilities and services as well as ontology development and management. WSMX platform extensively uses knowledge represented in the form of ontologies in order to provide for overall SWS execution lifecycle. Although the WSMT (Section 2) could provide partial support for the properties identified by this GC there are additional requirements that are not currently covered by the WSMX platform. The generality of the platform would require further customizations in order to support acquisition, retaining and accessing of the enterprise level knowledge (core competencies and process knowledge), formation and management of knowledge repositories and business intelligence.
3.4
Science Base for Enterprise Interoperability
The Science Base for Enterprise Interoperability GC assists in defining the EI as a scientific discipline by leveraging on both established and emerging sciences. The contribution of this GC in the definition of the EI framework properties is not of a direct nature. Nevertheless, SWS have their roots in a number of sciences, which form the EI science base: Networks and Communications, Cognitive science, Distributed Computing, Information Systems, etc. The comprehensive overview of the current trends, roadmaps and value propositions of the Enterprise Interoperability can be seen in [Le et al. 2006], [Le et al. 2008] and [Charalabidis et al. 2008].
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Use case
To justify the claims raised in previous section an overview of the use case representing a WSMX based solution addressing data and process heterogeneity reconciliation in B2B integration is presented. The scenario is the part of the SWS Challenge3 initiative. The Purchase order mediation scenario focuses on the data and process mediation problems of existing systems. In order to purchase goods service requester (Blue) must contact service provider (Moon). While Blue follows RosettaNet 4 specifications which govern message structures and protocols used in inter-enterprise information exchange, Moon internally uses proprietary legacy system in which data model and message exchange patterns differ from those of the RosettaNet. As depicted in Figure 2 an integration system should provide answers to the raised interoperability problems. The problem description includes definitions of messages that should be exchanged (in the form of XML Schema documents), examples of the messages and WSDL definitions of the Blue’s and Moon’s services. The detailed description of the scenario can be found at SWS Challenge Wiki5.
Figure 2 – Purchase order mediation scenario overview
The WSMX based solution of the problem consists of a number of artefacts compliant to the four basic WSMO elements. Leveraging on the definitions of messages, ontologies that describe main entities communicated between Blue and Moon are developed. Furthermore, Web services which consume these messages are semantically described (in terms of capabilities and choreographies relying on the ontologies). Additionally, lifting of the request messages from the syntactic XML-based format to the correspondent semantic WSML-based format is defined by the appropriate XSL transformations used by the adapters. Finally, request messages received from the Moon are expressed in the form of goals. The detailed description of the solution can be found in [Vitvar et al. 2007b].
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http://sws-challenge.org
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http://www.rosettanet.org
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http://sws-challenge.org/wiki/index.php/Scenario:_Purchase_Order_Mediation
Although WSMX based solution is not covering all aspects of the full-fledged EI framework (as envisioned by the GCs presented in Section 3) it tackles most of them, thus providing a foundational platform for solving problems found in the EI domain.
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Conclusions and future work
This paper presented WSMX as the platform to address selected EI problems. Based on the current trends and research roadmap as envisioned by EI Cluster 6 founded by European Commission the properties of the ideal EI framework are derived following identified EI GCs and covered research challenges. These properties are matched with the properties of the WSMX platform. It turns out that current state-of-the-art SESA implementation can provide the foundation platform for solving EI issues. A number of untouched issues still remain opened. The WSMX environment needs better integration with the repositories of enterprise level knowledge and systems for its acquisition, retaining and access. WSMX also lacks strong support for orthogonal services such as security, transactional behaviour and monitoring. As presented in [Shafiq et al. 2008] the research efforts of the IP COIN project 7 are aiming at enhancing WSMX with these scarce functionalities in order to develop a comprehensive EI framework. Acknowledgement This work has been partly funded by the European Commission through IP COIN: Collaboration and Interoperability for networked enterprises (Project No. 216256). The authors wish to acknowledge the Commission for their support. References Bussler, C; Cimpian, E; Fensel, D; Miguel Gomez, J; Haller, A; Haselwanter, T; Kerrigan, M; Mocan, A; Moran, M; Oren, E; Sapkota, B; Toma, I; Viskova, J; Vitvar, T; Zaremba, M; Zaremba, M. (2005) Web Service Execution Environment (WSMX), W3C Member Submission, June 2005. WWW page. http://www.w3.org/Submission/ WSMX, accessed 08.04.2008 Charalabidis, Y; Gionis, G; Hermann, K; Martinez, K. (2008) Enterprise Interoperability: Research Roadmap. Update Version 5.0. March 5th, 2008. WWW page. http://cordis.europa.eu/ist/ict-ent-net/ei-roadmap_en.htm, accessed 09.04.2008 Fensel, D; Lausen, H; Polleres, A; Bruijn, J; Stollberg, M; Roman, D; Domingue, J. (2007) Enabling Semantic Web Services: The Web Service Modeling Ontology, Springer-Verlag, 2007. Fensel, D; Kerrigan, M; Zaremba, M. (2008) Implementing Semantic Web Services: The SESA Framework, Springer-Verlag, 2008. Kerrigan, M; Mocan, A; Tanler, M; Fensel, D. (2007) The Web Service Modeling Toolkit - An Integrated Development Environment for Semantic Web Services (System Description), Proceedings of the 4th European Semantic Web Conference (ESWC), June 2007, Innsbruck, Austria Li, M; Cabral, R; Doumeingts, G; Popplewell, K. (2006) Enterprise Interoperability: Research Roadmap. Final Version 4.0. 31 July, 2006. WWW page. http://cordis.europa.eu/ist/ict-ent-net/ei-roadmap_en.htm, accessed 09.04.2008 Li, M; Crave, S; Grilo, A; Berg, R. (2008) Unleashing the Potential of the European Knowledge Economy: Value Proposition for Enterprise Interoperability. Final Version 4.0. 21 January 2008. ftp://ftp.cordis.europa.eu/pub/ist/docs/ict-ent-net/unleashing-potential-eke-final_en.pdf, accessed 09.04.2008 Shafiq, O; Komazec, S; Zaremba, M; Facca, F. (2008) Role of Semantic Web Services in Enterprise Collaboration & Interoperability, in Workshop on Interoperability and Cooperation of Organizations in Networked ecosystems (ICON'08), 4th International Conference Interoperability for Enterprise Software and Applications (I-ESA 2008), March 2008, Berlin, Germany.
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http://cordis.europa.eu/ist/ict-ent-net/ei.htm
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http://www.coin-ip.eu
Vitvar, T; Mocan, A; Kerrigan, M; Zaremba, M; Zaremba, M; Moran, M; Cimpian, E; Haselwanter, T; Fensel, D. (2007) Semantically-enabled Service Oriented Architecture: Concepts, Technology and Application. Service Oriented Computing and Applications, Springer London, 2007 Vitvar, T; Moran, M; Zaremba, M; Haller, A; Kotinurmi, P. (2007) Semantic SOA to Promote Integration of Heterogeneous B2B Services, in IEEE Joint Conference on E-Commerce Technology (CEC'07) and Enterprise Computing, E-Commerce and E-Services (EEE '07), IEEE, Tokyo, Japan, 2007. Zaremba, M; Moran, M; Haselwanter, T; Lee, H; Han, S. (2005) D13.4v0.3 WSMX Architecture, WSMX Working Draft 12.10.2005, WWW page. http://www.wsmo.org/TR/d13/d13.4/v0.3/20051012/, accessed 08.04.2008
