An adaptive model of virtual enterprise based on dynamic web service composition Bo Zhou1, Jing-fan Tang2, Zhi-jun He1 College of Computer Science & Technology, Zhejiang University, 310027 Hangzhou, P.R. China {bzhou, hezj}@zju.edu.cn 2 College of Computer Science & Technology, Hangzhou Dianzi University, 310018 Hangzhou, P.R. China
[email protected] 1
Abstract With the development of web services related technologies, the enterprise business systems can be encapsulated through web services. The service oriented architecture can be adopted for the enterprise business processes. Specific interfaces are introduced between the web services of different enterprises for data exchanging to achieve the cross-enterprise systems integration. Different enterprises can be organized into virtual enterprise through web services to share resources and achieve win-win. This paper introduces an adaptive model of virtual enterprise based on dynamic composition of web services (DCWS-VE). A service execution plan will be dynamically built to aim at the target of the virtual enterprise through the composition of web services. The development and deployment of web services is separated to support the dynamically deploying and binding of the web service at run time. The members in the virtual enterprise will be located through the dynamic web service discovery based on DAML+OIL logic reasoning, and selected through the dynamic web services negotiation with multi- steps protocol to organize the virtual enterprise at run time. Electronic contract is adopted in the organizing process of virtual enterprise to achieve the stable running.
1. Introduction With the development of technologies on workflow and enterprise information integration, more and more enterprises adopt workflow to automatically organize the internal business process and integrate all kinds of application systems to achieve the internal information integration. But traditional workflow system is not so effective for cross-enterprise information integration,
especially on complicate business systems. In order to join the virtual enterprise (VE) and build the communication with other enterprises, an enterprise should encapsulate the internal business system and business process to provide specific interfaces for cross-enterprise information integration. We hope the cross-enterprise workflow system can share and integrate all kinds of data and equipment resources, and also enable the automatically execution of business processes among the enterprises. With emergence of web services, it changes the ways of interaction between enterprises. The enterprise application systems can be encapsulated through web services. The service oriented architecture can be adopted for the enterprise business processes. Specific interfaces are introduced between the web services of different enterprises for data exchanging to achieve the cross-enterprise systems integration. Different enterprises can be organized into virtual enterprise through web services to share resources and achieve win-win. Based on the dynamic web service composition technologies, we present a novel model of virtual enterprise (DCWS-VE, Dynamic Composition of Web Services – Virtual Enterprise) in this paper. A service execution plan will be dynamically built to aim at the target of the virtual enterprise through the composition of web services. The development and deployment of web services is separated to support the dynamically deploying and binding of the web services at run time. The members in the virtual enterprise will be located through the dynamic web service discovery based on DAML+OIL logic reasoning, and selected through the dynamic web services negotiation with multi- steps protocol to organize the virtual enterprise at run time. Electronic contract is adopted in the organizing
Proceedings of the 2005 The Fifth International Conference on Computer and Information Technology (CIT’05) 0-7695-2432-X/05 $20.00 © 2005
IEEE
process of virtual enterprise to achieve the stable running. The rest of the paper is organized as following. Section 2 introduces the related work. Section 3 describes the whole architecture of DCWS-VE. Section 4 presents the target establishment process of virtual enterprise. Section 5 shows location of VE’s members, which is based on service discovery. Section 6 introduces the selection process of VE’s members, which is based on service negotiation. Section 7 concludes.
2. Related work There has been some research on the modeling of Virtual Enterprises to support services [4, 5, 6, 9]. A framework was presented in [4] to enable services that support the establishment, management and execution of business processes across VE boundaries. It utilized object-oriented technologies and distributed component-based development practices so as to ensure easy integration, customization and high degree of interoperability. In [6], it discussed the deployment of e-services in a networked enterprise setting. A framework was introduced to support fully webaccessible legacy system services with modern business services. It also argued in favor of three faceted services combing the following constructs: a service description language, a service request language and a functional specification language. A novel approach has been presented in [1] to address the problem of services composition and allocation in distributed environment, which caters for the dynamic changing of available distributed resources. Through service composition technology, the execution of the composite service is divided into the steps of processing series of element services, which can be seen as a workflow process. The factors of the pricing policy and trust are introduced in the evaluation of economic objective function, which is used to dynamically decide the allocation of the element services. Based on the research in [1, 2, 3], we will adopt the dynamic web service composition technology in the organization process of Virtual Enterprise, which includes the dynamic service discovery to locate the members and dynamic service negotiation to select the members.
1˅ Web service internal driven: the VE is organized due to the requirement of web service in some enterprise. For example, when the network finance management system in some enterprise wants to implement the functionalities of payoff, tax management and cash management, it should interact with the systems of bank and revenue office to organize a VE. 2˅ Business requirement driven: the VE is organized due to the business requirement advanced by some enterprise through the integration of several business systems (web services). For example, when some enterprise wants to invest on some fund, it should obtain the invest information of the fund such as stock, exchange and bond, etc. So it requires other organizations (i.e. stock exchange, bank) to be integrated to provide the related analysis information on the fund. In our model, it should first design services execution plan according to the business logic between the web services. Secondly, it will dynamically find out the available service providers as the candidate member enterprises at the running of the VE through the dynamic service discovery. Last, the manager will adopt the multi-steps negotiation with the candidate web services according to the synthetic evaluation function to decide the final member enterprise. Through the dynamic discovery and selection of web services, and after the electronic contract signed off, the VE will be organized dynamically. Figure 1 shows the organization process of VE in DCWS-VE. 5HTXLUHPHQWV 'HVLJQVHUYLFHVH[HFXWLRQSODQ
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3. Architecture overview Figure 1. Organization process of VE There are two ways in the organization process of virtual enterprise:
Proceedings of the 2005 The Fifth International Conference on Computer and Information Technology (CIT’05) 0-7695-2432-X/05 $20.00 © 2005
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4. VE’s target establishment For the establishment of virtual enterprise, a service execution plan should be built first according to the business logic whatever the VE is web service internal driven or business requirement driven. The execution sequence of the services will be decided in the plan to aim the VE’s target. There are specific dependence and time sequence between the web services to finish complicate business process. For example, when planning traveling, the plane ticket should be booked (plan ticket booking service) first to ensure the time to arrive at the destination. After that, the restaurant can be ordered (restaurant ordering service) according to the time to arrive at the destination. For the web service internal driven VE, we can organize the element web services based on workflow according to the invoking sequence of the web services to build the services execution plan. For the business requirement driven VE, we can do intelligent analysis on the requirement, and decide the functionalities of the key business processes (web services) for the requirement implementation. After that, we can build the services execution plan according to the internal relationship between the element web services.
four types of registered services: classification system, identity system, abstract interface module and criterion. tModel is the carrier and presentation of the registered data of these web services in UDDI center. It is the metadata of the web service description. All the tModels involved in the web service compose the technique identity of the web service. Through the analysis on the technique identity, we can find out which type of technique criterion the web service adopts and what interface the web service uses, etc. As shown in Figure 2, some elements in tModel are described through the information of service interface description from WSDL. If the WSDL document of web service is not registered in UDDI, a new tModel will be created to present the interface. tModel should have the name of URI and link the location of WSDL document. Binding template is used as the specific implementation of one tModel or multi tModels, which provides registration of specific accessing point. UDDI allows the separation of interface and implementation just like WSDL architecture. So tModel can be published separately from the binding template. For example, one organization may publish the criterion interface for specific business and more than one organization can program the implementation for the interface, which will refers to the same tModel.
5. VE’s member location In DCWS-VE, it will build the UDDI center for virtual enterprise. All the enterprises and related web services should register to the UDDI center, which is like an enterprise resource repository. Furthermore, since we support the separation of development and deployment of web services [1] in DCWS-VE, there are some web services in UDDI center which will need to be dynamic deployed at running time. The available servers will be chosen according to the environment configuration information in the description of web services. So the UDDI center should allow the enterprises to register and dynamically update the server related information (i.e. service price policies, available service shares, etc). In order to publish and discover the web service description in UDDI center, the WSDL document is classified into two types: service interface and service implementation. Before the service implementation is published, the corresponding service interface should be published in UDDI center as a tModel [7]. tModel is a glossary integrated with several concepts. According to the description in UDDI, tModel is used to define the technique criterion of web service. In current implementation of UDDI, there are
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Figure 2. Mapping from WSDL to UDDI Service implementation is published in UDDI center as enterprise web service with one or multibinding template. Figure 3 shows an example of service implementation for simple workflow activities.
Proceedings of the 2005 The Fifth International Conference on Computer and Information Technology (CIT’05) 0-7695-2432-X/05 $20.00 © 2005
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Figure 3. A document of service implementation A new business service will be created for each service element defined in the service implementation document. An example of WSDL document for business service is shown in Figure 4. EXVLQHVV6HUYLFHEXVLQHVV.H\ āāVHUYLFH.H\ āā! QDPH!:RUNIORZ,PSO6HUYLFH QDPH! GHVFULSWLRQ[PO ODQJ āHQā!$VLPSOHDFWLYLW\LPSOHPHQWDWLRQ GHVFULSWLRQ! ELQGLQJ7HPSODWHV! ELQGLQJ7HPSODWHELQGLQJ.H\ āāVHUYLFH.H\ āā! GHVFULSWLRQ!6LQJOH$FWLYLW\6HUYLFH GHVFULSWLRQ! DFFHVV3RLQW85/7\SH āKWWSā! KWWS ZRUNIORZZHEV DFFHVV3RLQW! W0RGHO,QVWDQFH'HWDLOV! W0RGHO,QVWDQFH,QIR W0RGHO.H\ ā88,' '&$)& 7&8()ā! LQVWDQFH'HWDLOV! RYHUYLHZ85/! KWWS ZRUNIORZZHEVDFW,PSZVGO RYHUYLHZ85/! LQVWDQFH'HWDLOV! W0RGHO,QVWDQFH,QIR! W0RGHO,QVWDQFH'HWDLOV! ELQGLQJ7HPSODWH! ELQGLQJ7HPSODWHV! Ă EXVLQHVV6HUYLFH!
Figure 4. A WSDL document of business service VE’s manager will dynamically discover the web service according to the services execution plan to organize the VE. A matching engine of web service will be adopted in the process of service matching, which is based on DAML+OIL [8] logic reasoning. When manager sends request to UDDI center, UDDI center will convert the request into service profile and send it to matching engine, which will use the DAML+OIL reasoning machine to do the flexible matching on functionality description through DAML ontology and web service description.
In DCWS-VE, we support two kinds of web service discovery [3]: one is to discover the available service provider to provide the service according to the functionality description and other knowledge (i.e. interested domain, category, etc); the other is to discover the available server to dynamically deploy the web service to provide the service according to the configuration information of running the service described in the service description. When we try to find the available service provider to provide the service, more than one service provider will be found in UDDI center to provide the service implementation. These service providers will be chosen as candidate members to attend the service negotiation process. When we try to find the available server to dynamically deploy the service, more than one server registered in UDDI center will be found, which will be chosen as candidate members to attend the service negotiation process.
6. VE’s member selection Since there is more than one service provider (or server) to be discovered, manager will select one to as member to organize VE. From the aspect of candidate member, it will choose to join the VE which it is interested in. So, service negotiation process will be executed between manager and candidate members to finish the selection of final member enterprise to organize VE.
6.1. Service negotiation model In DCWS-VE, we adopt tender/contract-net model [10] to achieve service negotiation process. We allow the service provider to dynamically adjust the service quality parameter and related quote to provide multibids. Manager will adopt the multi- steps negotiation protocol according to the service evaluation function provided by experts and decide the final member during the period of the negotiation. When the manager publishes the bid, it will have some expectation for the parameters of service (i.e. QoS) and related cost, which will be decided the expert’s knowledge and experience. Service evaluation function [1] will be generated finally to evaluate the synthetic parameters to address the selection strategy. In each enterprise, a trust table will be maintained to record the reputation of other enterprises, which will be used as a parameter in service evaluation function. During the period of the negotiation, manager will perform evaluation on each bid from service providers
Proceedings of the 2005 The Fifth International Conference on Computer and Information Technology (CIT’05) 0-7695-2432-X/05 $20.00 © 2005
IEEE
and adjust its selection strategy dynamically to achieve optimization of service evaluation function. When the duration of the negotiation ends, manager will evaluate the final bids provided by candidate members and select the most optimum candidate member as final member to organize VE. Figure 5 shows the process of dynamic service negotiation.
sections: contract characteristics, technical section, administrative domain section and pricing section.
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