E-DREAM: A Web-Based Platform for Virtual Agile Manufacturing

Concurrent Engineering http://cer.sagepub.com

E-DREAM: A Web-Based Platform for Virtual Agile Manufacturing Dunbing Tang, Li Zheng, Kwai-Sang Chin, Zhizhong Li, Yulan Liang, Xiaojian Jiang and Changjian Hu Concurrent Engineering 2002; 10; 165 DOI: 10.1177/1063293X02010002698 The online version of this article can be found at: http://cer.sagepub.com/cgi/content/abstract/10/2/165

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CONCURRENT ENGINEERING: Research and Applications E-DREAM: A Web-Based Platform for Virtual Agile Manufacturing Dunbing Tang,1,* Li Zheng,1 Kwai-Sang Chin,2 Zhizhong Li,1 Yulan Liang,1 Xiaojian Jiang1 and Changjian Hu1 1

Department of Precision Instruments and Mechanology, Institute of Manufacturing Engineering, Tsinghua University, Beijing, 100084, P.R. China 2

Department of Manufacturing Engineering and Engineering Management, City University of Hong Kong, Hong Kong, P.R. China

Abstract: In the emerging agile manufacturing paradigm, there is a great need for a flexible and re-configurable IT platform to form virtual enterprises. In this paper, according to the functional requirements of virtual agile manufacturing, a pragmatic Web-based platform entitled ‘‘E-DREAM’’ has been developed to support the virtual enterprising. Firstly, this paper discusses the E-DREAM basic architecture, infrastructure, and the global object model of E-DREAM. Next, based on the information, information interaction, and role classification, the distributed information management and role management in E-DREAM are interpreted, illustrating that the information access visibility level is dependent on the role that an agile partner plays in a VE (Virtual Enterprise). Making use of CORBA-based method, the implementation of wrapping software resources is conducted, which aims at interoperating the remote software resources. In the end, the E-DREAM prototype implementation is presented. Through the E-DREAM architecture development and prototype system implementation, we have come up with a thorough approach for building agile virtual enterprises, configuring and re-configuring working platforms for different agile partners. Key Words: agile manufacturing, virtual enterprise, distributed information management, internet/web, CORBA.

1. Introduction The manufacturing business environment is characterized by increasing turbulence. Customer requirements, product designs, suppliers, manufacturing equipment, and trade regulations continually change. The speed of change in demand, seasonal trends and customer requirements is increasing. Thus, the product life span is decreasing while the product variety gets more complex because of diversified customer requests. Companies are forced into continuous measures of actions to reach their goal of sustainment and further successful development. ‘‘No company is an island!’’ Therefore, companies need to consider more than their own business processes to secure their future development, to improve their capability, and to reduce constraints limiting the decision-making. Improving a company’s manufacturing capability and consequently its posture in global markets requires that a company respond more rapidly to market opportunities. Improving manufacturing requires new levels of flexibility and responsiveness in identifying and addressing emerging

*Author to whom correspondence should be addressed. E-mail: [email protected]

market opportunities; this capability is often referred to as cooperation and agile manufacturing. Agile Manufacturing makes use of modern information technology to form Virtual Enterprise (VE), which agilely responds to the changing market demands [1]. A virtual enterprise, different from a traditional enterprise, is a temporary consortium or alliance of companies formed to share costs and skills and to exploit fast-changing opportunities. It is productoriented, team-collaboration styled, and featured as fast and flexible. A traditional enterprise is constrained by internal and external boundaries, whereas virtual enterprising requires an enterprise to break both internal and external boundaries, and be created and reconfigured with a world-wide scope in flexible and optimized mode in order to meet the requirements of the rapidly changing markets. Agile manufacturing or virtual enterprise focuses on enhancing competitiveness by cooperating working. Cooperation among production companies and agile manufacturing are nothing new. Over the past years, the intensity of cooperation has increased and its scope has broadened. The rapid progress of information technologies that support the cooperation has enforced this development. New terms like telecooperation, computer-supported cooperative work, or groupware

Volume 10 Number 2 June 2002 1063-293X/02/02 0165–19 $10.00/0 DOI: 10.1106/106329302027698 Downloaded from http://cer.sagepub.com at PENNSYLVANIA STATE UNIV on April 14, 2008 ß reserved. 2002 Sage © 2002 SAGE Publications. All rights Not forPublications commercial use or unauthorized distribution.

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describe concepts and technologies that significantly help in establishing cooperation. The rise of the Internet has contributed to facilitating global communication. The Internet technology has evolved very rapidly over the last years. Due to its multimedia capability, the World Wide Web (WWW or Web) is the most popular and visible component of the Internet. The advent of WWW techniques has sparked new activities among researchers into the development of web-based product design and manufacture systems [2–4]. The rapid growth of the Web technology, with its widespread acceptance and accessibility, also has resulted in the emergence of Web-based Agile Manufacturing [5]. In agile manufacturing enterprises, frequent and dynamic interactions among partners, partner software systems interoperability, partner information management, and cooperation coordination bring new challenges to the development of Web-based Agile Manufacturing. Supported by Natural Science Foundation of China, a project entitled ‘‘Web-based Technologies Enabling Agile Manufacturing’’ addresses the challenges of improving cooperated design and manufacturing responsiveness and flexibility by establishing Webbased systems to support application tools integration and enterprise-wide communication. In this project, a virtual working platform entitled ‘‘E-DREAM’’ is created as the base for the implementation of Webbased agile manufacturing. The remainder of this paper is organized as follows. In Section 2, we review the relevant research about agile manufacturing and virtual enterprise. Section 3 presents the characteristics and requirements of E-DREAM. Section 4 is devoted to the overview of E-DREAM, including related concepts, E-DREAM basic architecture, as well as the global object model of E-DREAM. In Section 5, a distributed information management system is proposed based on the information and information interaction classification. Section 6 conducts the role management and working space management, illustrating that the information and resource access visibility level is dependent on the role that an agile partner plays in a VE. Section 7 interprets how to wrap the software resources using CORBA-based technology. A brief description of the E-DREAM prototype implementation is included in Section 8. Section 9 discusses the relationship between E-DREAM and Concurrent Engineering. Finally, we conclude with our contributions and future work in Section 10.

2. Relevant Research Review The organization in production management is an issue facing increasing complexity. While twenty years ago single functions of companies were analyzed, later the focus was laid on business processes that connect

ET AL.

the business functions. Beginning with the market or the customer respectively, the processes explained the order of tasks to transform the raw materials into finished products that are delivered to the customer [6]. In the 90s, system theory strongly influenced the process management. Instead of examining single processes, nowadays, networks of interacting processes are analyzed. The processes are not fixed anymore. They rather develop and change continuously. A competitive order processing requires a holistic approach. The awareness that every problem in one business function in any company involved in the order processing can affect the whole chain, leads to corporate networks where companies cooperate aiming at improving the overall performance of the network. In the last decade, Enterprise Integration has been given much more attention in the academic and industrial organizations [7,8]. In general, Enterprise Integration focuses on the information integration inside traditional enterprises [9], while along with the development of computer networks (such as Internet/Intranet) and information technology, the rapid changes of market and user requirements require the manufacturing to become a global undertaking. Agile manufacturing and virtual enterprising are viewed as most promising business for manufacturing industries to meet global competition. Agile manufacturing is attracting an increasing amount of attention from both the academic and industrial communities over the past several years. The definition of ‘agile’ is not clear and consistent. Noaker considers that ‘‘agility’’ is the measure of a manufacturer’s agility to react to sudden, unpredictable change in customer demand for its product and services and make a profit [10]. Comerford is convinced that factories that are agile at tailoring goods to customer requirements without halting production are coming on line [11]. Goldman and Nagel consider that agile manufacturing assimilates the full range of flexible production technologies, along with the lessons learned from total quality management, ‘just-in-time’ production and ‘lean’ production [12]. Gunasekaran deems that agility is about casting off those old ways of doing things that are no longer appropriate – changing pattern of traditional operation [13]. Quinn et al. conclude that the only common thread among various definitions is the ability to manufacture a variety of similar products based on what may be rapidly changing customer needs [14]. In the new and emerging agile manufacturing paradigm, where multiple firms cooperate under flexible virtual enterprise structures, there exists a great need for a mechanism to manage and control information flow among collaborative partners, and the incompatibility of information processing systems and technology is one of the major inhibitors to agile manufacturing. In response to this pressing need, today, in the USA,


E-DREAM: A Web-Based Platform for Virtual Agile Manufacturing

the National Industrial Information Infrastructure Protocols (NIIIP) Consortium is using virtual enterprise technology to develop a common manufacturing information infrastructure to enable data sharing and agility [15]. The NIIIP Consortium consists of leading United States information technology suppliers and users with the common goal of developing software architecture and providing technologies to enable virtual enterprises. Virtual enterprises are temporary joint ventures or alliances of organizations that form to exploit fast-changing opportunities. The operations of a virtual enterprise are transparent of physical location/ proximity of participants and resources. The NIIIP Consortium operates on a national basis and its virtual enterprise technology is based on an open architecture using emerging, existing, and defacto industry standards. The basic building blocks used by NIIIP to enable the virtual enterprise are: Internet (HTTP, TCP/IP) – for communication connectivity, Object Management Group Common Object Request Broker Architecture (OMG-CORBA) – for application interoperability, International Standard Organization Standard for the Exchange of Product Model Data (ISO-STEP) – for information sharing, and Workflow – for process and work management. The National Institute of Standards and Technology (NIST) has conducted a famous project entitled ‘‘TEAM (Technologies Enabling Agile Manufacturing)’’ (http://www.nist.gov). This project aims to ally the power of academics, governments, and industries to implement agile manufacturing. In TEAM of NIST, the virtual enterprise is enabled by the integration of Product Design & Enterprise Concurrency, Virtual Manufacturing, Manufacturing Planning & Control, and Intelligent Closed-Loop Processing. The Electric Agile Manufacturing Research Institute (EAMRI) at Rensselaer Polytechnic Institute (RPI) is focusing on electric product realization in distributed manufacturing environments using improved infrastructures and architectures [16]. At Europe level, an ESPRIT project, PRODNET II, aims at designing and implementing a federated database architecture as the base support framework to effectively manage certain issues associated with the sharing and exchange of information in the VE environment, such as the physical distribution of data, the enterprise autonomy and privacy enforcement, access rights to shared information, and data visibility levels, among others [17]. Sandakly et al. have proposed a new approach to building a virtual enterprise software infrastructure that offers persistence, concurrent access, coherence and security on a distributed datastore based on the distributed shared-memory paradigm [18]. This approach generated a platform of persistent, distributed and shared memory called PerDiS. In PerDiS, memory is shared between all applications, even located at different sites or running at different times. Based on

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an ESPRIT project (X-CITTIC) [19], Zhou et al. have proposed a distributed information management architecture for production planning in a virtual enterprise using CORBA standard and client-server technologies. However, no implementation or prototype of the architecture has been found in publications. Pallot and Sandoval have presented concurrent enterprise as a tactical approach for collaborative working between trading partners. It consists of defining and implementing collaboration activities using a shared process, common services, and virtual spaces for electric collocation [20]. At Asia level, based on concurrent engineering and virtual enterprise, Chen et al. have carried out the research on allied concurrent engineering through distributed engineering information management. They believe that the integration, management and sharing of engineering information are the basis for allied concurrent engineering, and their research focuses on some systematic approaches to express the functional requirement analysis, system design and modeling [21,22]. Zhang et al. present the concept of enterprise virtualization. They consider that enterprise virtualization is the link between enterprise integration and virtual enterprise, and the focus of their paper is on the virtualization of an enterprise [9]. Zhang et al. have paid attention to Web-based technologies enabling agile manufacturing [5]. Current agile manufacturing and virtual enterprise researches mainly emphasize the architecture design, functional requirements, system approaches, and interpreting some new concepts. However, the working platform or environment is the basis for implementation of agile manufacturing or virtual enterprising. Our work provides a flexible virtual working platform entitled ‘‘E-DREAM’’, which supports virtual agile manufacturing through partner information sharing, software tools inter-operability, working space configuration and re-configuration, and distributed information management using Internet technologies.

3. The Characteristics and Requirements of E-DREAM The concept of agile manufacturing can be realized by the capabilities (from the quick integration of valueadded activities from allied enterprises into a value chain) to reflect the changes in product design and manufacturing processes [22]. When a business process is executed by an allied virtual enterprise, parts of the decomposition of the business process are assigned to different partners. The difficulty is that subprocesses of the business process might be performed by different actors (different members of the virtual enterprise) that have different priorities and motivations, and


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different perception of the working environment. To support a consistent working environment for the partners of virtual enterprise, the objectives of E-DREAM are listed as follows: 1. Providing flexible and re-configurable working platforms on which the partners can select their required resources In traditional enterprises, there exists a single set of resources within the company’s scope, and people face a fixed resource operation platform. However, in a virtual enterprise, partner should dynamically configure his/her working platform and resources to meet the changing market needs. Meanwhile, an agile partner in a virtual enterprise is dependent and independent. It is dependent in the sense that it cooperates with others to develop a product; it is independent in the sense that it has full autonomy in executing its polices. Thus the working platform should be flexible so as to reflect partner cooperation and autonomy policies. 2. Providing flexible schemes and open architecture to create virtual organizations Actually, partners of a virtual enterprise have different business rules and information infrastructures. To create a virtual organization, a partner has to adapt its information infrastructure to the virtual enterprise common architecture so as to share and exchange project data with other partners. This requires that the architecture should be open and easy to adapt new infrastructures. 3. Providing a mechanism for distributed information sharing and management In a virtual enterprise, the information is segmented and distributed across the distributed sites of partners who need to access the information frequently and dynamically. Distributed information sharing and communication are essential to support the agile product development. Meanwhile, partners at different right-levels have different ownership of the common information such as product data and knowledge. Thus, it is up to the E-DREAM to maintain the information access control and data security, ownership and responsibility. 4. Providing resource assignment method to partners Distributed activities are performed by different actors using different resources. The resources assigned to one partner may be inside an enterprise, may be across enterprises. The optimization of resource request and assignment needs an effective decision method. In addition, interactions and cooperation between diversity of roles, such as VE member and coordinator, also require a flexible coordination mechanism. 5. Exploring a wrapping technology to make the distributed software tools inter-operable Software engineering is entering the stage of component-based

ET AL.

solution supported by distributed object technology. A component is a reusable object that can be integrated into an application without any need to know how the object is implemented. CORBA is one of the most popular distributed object technologies. It is a language-neutral model enabling distributed object interoperation across different networks, machine types and operation systems. The interface of a CORBA object is completely separated from its implementation. In the E-DREAM platform, we use CORBA to wrap the distributed software tools.

4. Overview of E-DREAM 4.1. Related Concepts of E-DREAM Some related concepts of E-DREAM and the relationship among them are defined as follows. Enterprise virtualization: Enterprise Virtualization is a mapping process through which key elements are mapped from limited real space to unbounded virtual space so that the entities of enterprise become visible, manageable, and potable in virtual space [9]. Virtual Enterprise is the temporary alliance of some virtualized enterprises. The relationship among real enterprise, virtualized enterprise and virtual enterprise is described in Figure 1. Also the relationship can be illustrated as the following formulas: n [

VIEi

ð1Þ

VIE ¼ f ðRE, aÞ

ð2Þ

VE ¼

i¼2

where RE ¼ ½RR, RP, RWE, CT

ð3Þ

T

ð4Þ ð5Þ

VIE ¼ ½VR, VP, VWE, C f ¼ ½ fR , fP , fWE , fC

Figure 1. The relationship among RS, VIE and VE.


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where VE RE VIE RR VR RP VP RWE VWE C f a

stands stands stands stands stands stands stands stands stands stands stands stands

for for for for for for for for for for for for

changing, the mapping process is nonlinear and needs more than one iteration. The enterprise virtualization process is not fixed due to different behaviors and knowledge of people. Therefore, the mapping process is controllable using the mapping control vector a. On the one hand, enterprise virtualization is a mapping of enterprise integration in real space. On the other hand, it is a base and condition for building a temporary virtual enterprise.

Virtual Enterprise; Real Enterprise; Virtualized Enterprise; Real Resource; Virtualized Resource; Real Process; Virtualized Process; Real Working Environment; Virtualized Working Environment; Coordination; the mapping function; the mapping control vector.

4.2. The E-DREAM Basic Architecture Considering the cooperative business practices and the emerging agile environment, we propose the E-DREAM basic architecture shown in Figure 2 emphasizing the main components involved in virtual enterprising. Cooperation, collaboration, and flexibility are the basic fundamentals of E-DREAM. The success of virtual enterprising is dependent on process integration. In VE, the process integration is concerned with the integration of the activities of the product development process though enterprise alliance. At first, a process model is planned and configured by integrating the value-added activities based on the characteristics of a given product for development. Next, a sharing virtual process is created by selecting one or more partner enterprises for each sub-process based on their capabilities. Meanwhile, the sharing virtual process is equipped with wrapped resources such as software systems and databases. Using CORBA technology, the virtualized resource request and assignment for each sub-process can be operated remotely. E-DREAM also provides the appropriate support for the interactions among partners in a VE environment. As a VE is composed of several partners with heterogeneity, it must work as a single unit. A coordination/management function is required for them in order to facilitate their harmonic operation and to achieve the desired operation.

Virtualized Process: A process is virtualized when it is composed of activities which are performed by different allied enterprises, and then it can be configured by integrating those value-added activities based on the varying capabilities of allied partners. Virtualized Resource: VR means that the resource is registered into network-based repository using wrapping technology, and it can be inter-operated and controlled by remote partners. Virtualized Working Environment: VWE is a logical workspace for each team member. In E-DREAM, the user can register and configure his/her special VWE by selecting different resources. The E-DREAM has built a template working environment. According to the role in a VE, the user can re-configure his/her working space (or working area) based on the template working environment. Coordination: Coordination is managing dependences between activities performed by different partners, communication among VE members, invocation decision of services of VR, and distributed information management. In E-DREAM, the enterprise virtualization or mapping process is supported by the Web-based network. As the marketing requirements are dynamically

Wrapped Resource

Wrapped Resource

Wrapped Resource

CORBA

Process Modelling

Sharing Infrastructures Virtual Working Environment Virtual Product & Process

Marketing Needs Coordination Partner

Partner

Partner

Figure 2. The E-DREAM basic architecture. Downloaded from http://cer.sagepub.com at PENNSYLVANIA STATE UNIV on April 14, 2008 © 2002 SAGE Publications. All rights reserved. Not for commercial use or unauthorized distribution.

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Corporate Servers Web servers Application servers HTTP

Internet

Infrastructure CORBA servers

Applet

Workflow management and task coordination Distributed engineering information management

IIOP

Virtual team generation and roles management Working space configuration

Web clients HTML

ET AL.

... ORB

Resource registration and management

Figure 3. Sharing Infrastructure and virtual working environment of E-DREAM.

To support the collaboration and interaction among agile partners, E-DREAM provides distributed and shared infrastructures that constitute a virtual working environment. The infrastructure includes (see Figure 3): . . . . .

Workflow management and tasks coordination; Distributed engineering information management; Virtual team generation and roles management; Working space configuration; Resource registration and management.

As there is an identified need for interaction between agile partners or virtual teams, there will be a need to exchange information. To support both synchronous and asynchronous interactions, E-DREAM uses the Internet and Web-related technologies enabling the implementation of virtual working environment. From Figure 3, we can see some components that contribute to an open and virtual working environment. The virtual working environment can be categorized into three levels: web client level, corporate server level, and global level. At the web client level, the individual partner can use the browser to access the information and resources needed for his/her computed tasks, and the resources are specific to his/her platform. At the corporate level, there are network level services to serve the individual user, and the network level services are implemented by web servers, application servers, as well as CORBA services, which are platform and operating system independent. At the global level, some open Internet standards such as HTTP, TCP/IP, and IIOP are used to provide communication, security and interoperability protocols. 4.3. Object Modeling of E-DREAM Using UML (Unified Modeling Language), Figure 4 shows the global object model of E-DREAM and describes the relations among its sub-models. The E-DREAM virtual platform consists of four submodels: virtual working environment, virtualized

resources, virtual process, and distributed information. Virtual working environment provides one or more personal working areas. According to different actors, the personal working area can be divided into administrator working area, project working area, team working area, and team member working area. The administrator working area is for the administrator to manage the E-DREAM platform. The project working area is for the project leader to coordinate, monitor, and check the product development process. The team working area is a common working space which can be shared by all team members. The team member working area is private to team members, where information and resource items within it cannot be shared unless they are released to the allied team library. Virtualized resource is an important element of E-DREAM platform, and virtualized resource management is the main component required to implement a virtual working environment. Through virtualized resource configuration, the user can select and subscribe to the required resources in order to configure his/her specific work-space. The virtualized resource management consists of resource wrapping, resource registration, resource request, resource supervision, and resource assignment. The resource wrapping is to make a resource operable and manageable in the virtual space. Resource registration is to store the general information of resource (such as name, function description, owner, resource server, etc.) in a repository for inquiring and query. Resource assignment means that the team supervisor at first identifies the resource request from a team member, then make a decision and make the user access the required resource or not based on the applicant’s authority. The resource supervision is to control and check the working state of virtualized resources. Distributed information involved in virtual enterprising can be summarized into flow information (such as product and process data), communication information (such as e-mail, message, discussion), and other activity



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Figure 4. Object Modeling of E-DREAM.

reference data (such as material data, project documents, company historical data) [22]. Distributed information management in E-DREAM aims to support partner information sharing and to keep the dispersed information consistent. Also, the information access control is the necessary procedure to ensure individual partner information securities. Most of the information is basically the outputs of engineering process; namely, the virtual process creates distributed information. A virtual process in E-DREAM consists of basic activities. The workflow management and activities coordination control the dynamic process adaptation and ensure effective information sharing and exchange between different agile partners.

issues such as the physical distribution of data, access rights to shared information, information visibility levels, as well as partner information interoperability bring new challenges to information management. As the virtual enterprise structure is composed of several physical distributed enterprises, we propose a distributed information management methodology in E-DREAM. Distributed information management is based on such facts: (1) the agile partners are autonomous; (2) not all partners of a VE play the same role and not all of them have the same access level to the information stored in other partner enterprises.

5.1. Information Classification and Information Interaction in VE 5. Distributed Information Management When designing the E-DREAM platform aimed at supporting virtual enterprising, certain information

In order to facilitate distributed information management, the first step is to analyze and classify the engineering information depending on the information


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applications. The information E-DREAM are as follows:

categorizations

in

1. Private information: This type of information is not shared with other partners; it is intended to be accessed only for local processing. 2. Public information: Information accessible by all other partners. 3. Information for team members: A subset of the data that needs to be accessed by other members of a team. 4. Exchanging information: The information between partners of a VE such as the sending and reception messages. 5. Interoperable information: This information not only can be remotely accessed, but also can be interoperated and changed remotely by other partners. Due to the information classification, there are four information interaction types between partners of a VE: browsing, exchanging, half-interoperating, and interoperating (see Figure 5): 1. Browsing: It is the lowest level of information interaction. For instance, through Internet, general description of a partner enterprise that in a way advertises the company, is made accessible to the public. 2. Exchanging: Through exchanging interaction, one partner can obtain acquaintance information from other remote partners to serve internal purposes. For example, a leading agile partner owns the end product, and he/she can download the standard part (such as bolt, nut) model from other outsourcing enterprises and use it as his/her own part model to finish the product development process. 3. Half-interoperating: The half-interoperating interaction means that one partner can get some productrelated issues (such as product model) from a ‘‘sister’’ company. After changing or modifying these issues, he/she can transmit them back to a specified destination. Meanwhile, a message will be sent concurrently as a notification. 4. Interoperating: It is the highest level of information interaction. Through interoperating interaction, one partner can directly access the required product model and has the full right to operate it on-line.

Figure 5. Four types of information interaction.

ET AL.

5.2. Distributed Information Management System Within Virtual Enterprise Taking into account the classification of information and information interaction described above, Figure 6 gives a snapshot of a virtual enterprise architecture emphasizing the distributed information management system. DIMS (Distributed Information Management System) for every partner includes such models: Information Client, Information Sever, Local Coordinator, Communication Management, Local Information Repository, and Query Management. The Information Server is responsible for receiving queries from the Information Clients of other partners, then interacting with the Query Management to execute the queries and sending the results to the inquirer. The Information Client sends the subqueries to other partners and receives the results. The Local Coordinator executes and controls the information flow which can be defined as a collection of subqueries, and determines whether the query is local query or external query. If the query is a local one, the Local Coordinator will invoke the workflow to internal query management. If the query is an external query, it will decompose the query into subqueries which are sent to external partners by Information Client. The Query Management further divides into Partner Identification, Accessibility Control, and Query Processing. The Partner Identification is to analyze the arriving query in search of specification of partner roles corresponding to other partners. The Accessibility Control is referred to support the information visibility level mechanism according to different partner roles. For example, the VE project leader needs to know some information, which to another regular partner may even be a secret. The Query Processing is to process the subqueries and merge the sub-results into a global result, and sends it to the inquirer. The Communication Management takes care of communication between the information system and the application system. The repository stores local primitive information and forms a part of the partner primitive information storage. As the VE infrastructure cannot impose right rules to the companies, it must be configurable in order to support a variety of scenarios. This agile virtual enterprise should be open, and a partner can connect and disconnect from a VE. Meanwhile, the working partners should have full autonomies, and they can cooperate with each other through mutually agreed information sharing and management schema. Using the distributed information management approach proposed above, agile partners are able to collaborate flexibly and dynamically, and can maintain the uniformity, security, and authenticity of information sharing and exchange among them.



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Figure 6. Virtual Enterprise architecture and distributed information management system.

6. Roles Management and Working Space Management As described above, the information access right is dependent on the role that an agile partner plays in a VE. In the E-DREAM platform, the user roles are divided into four classes: Administrator, Project Leader, Team Supervisor, and regular member. Every VE partner will be assigned a specified role. The hierarchal relationships between them are described in Figure 7. There is an administrator who is responsible for managing the E-DREAM platform. The virtual enterprise generation action is based on the E-DREAM platform. For every virtual enterprise, there is a leading enterprise that owns the end product of a virtual process and is in charge of the process. The project configuration and workflow management belong to the leading enterprise. We assume it as the project leader. To finish a product development in a VE, several virtual integrated teams are created to perform the product life cycle tasks. The virtual team is generated by team members who are crossed partner enterprises. The information stored in a partner enterprise is not available with same visibility level to all VE roles. In other words, the information visibility can be defined differently for every role. The administrator is only responsible for managing the Web-based environment, accepting and ratifying the virtual enterprising application from a project leader. He/she has not right to access

Figure 7. Relationships between different roles in Virtual Enterprises.

any information of a virtual enterprise. The project leader has more accessibility to other partner’s data related to VE than a simple regular VE partner because of its control, monitoring, and auditing responsibility. A virtual team supervisor is in charge of a specific subtask inside a VE, will has more access visibility to certain partners information than other regular members, but more limited than the project leader. A regular member can access other partner’s information only with authorization. In E-DREAM, when a user has finished registration, a default working space (or working area) will belong to him/her. In the default working space, there are some common components or software tools. After logging in with username and password, the client user can download the responding working space. Due to different roles in VE, the function of working space is


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ET AL.

Figure 8. Functions of different working spaces in E-DREAM.

different (see Figure 8). In the administrator working space, the administrator is in charge of user registration management, resource registration management, as well as project registration management. In the project leader working space, the project leader of a VE will take care of virtual team generation and deletion, and process configuration and coordination which can monitor the status and performance of all VE partners. In the team supervisor working space, the team supervisor is responsible for team member management, subtask supervision, and resource assignment. In the regular member working space, the user can view and subscribe to the resources within a team. When the subscribed resources application is approved by the team supervisor, the member working space will be configured and the subscribed resources can be downloaded to it.

7. Implementation of Wrapping Software Tools in E-DREAM From the viewpoint of wrapping technology, the resources in an enterprise can be divided into two classes: the resource that can be wrapped (such as software systems and database) and others that cannot be wrapped (such as machines, tools, and people) [9]. In order to make the wrapped resource sharable and interoperable in E-DREAM, we make use of CORBA

technology to wrap the software tools. To implement an agile virtual enterprise, distributed applications often consist of several communication programs written in different programming languages and running on different operating systems. Network programmers must consider all of these factors when developing applications. The CORBA defines a framework for developing object-oriented, distributed applications. This architecture makes network programming much easier by allowing the user to create distributed applications that interact as though they were implemented in a single programming language on one computer. We use a practical example to explain the method of CORBA-based software tools wrapping. As we know, Rule-based reasoning (RBR) has wide application in product development. Inference engine is the kernel of a rule-based system. It is valuable to develop a reusable, shared and interoperable inference engine software component for wide application purposes. In E-DREAM, CORBA-based OrbixWebTM (http:// www.iona.com) is adopted to wrap the inference engine into a component accessible across different platforms that product development applications may reside in. The component provides reasoning service on the Internet and can be integrated into various applications. In the Computer Aided Process Planning (CAPP) framework system THCAPP-FS [23], the RBR reference engine has been developed using C/Cþþ language in UNIX platform. In order to wrap the RBR inference



RBR.idl

IDL Compiler

Generated Classes and Interfaces

_RBRStub

_RBRSkeleton

Java/C++ Complier RBR Client Application

RBR Object Implementation

Client Bytecode

Server Bytecode

Figure 9. Overview of the compilation of the RBR interface.

engine by CORBA-based method, Figure 9 shows the overview of the compilation of the RBR interface, and which includes the following programming steps: 1. Define a standard RBR interface in CORBA/IDL (Interface Definition Language) which is an implementation language-independent specification: //RBR.IDL interface RBR { readonly attribute string ServerName; readonly attribute string Description; readonly attribute string UpdateInfo; //operations of rule-based reasoning//rules and facts given by files and result(new facts) stored in a file short ffRuleInfer(in string RuleFile, in string FactFile, in string ResultFile); //rules and facts are given by strings and result(new facts) stored in a stringshort ssRuleInfer(in string Rules, in string Facts, out string Results); }; The readonly attributes provide basic information of the object. A client can know the information, identify the object or check its revision status from them. Two methods are provided for rule-based reasoning. One can be called by file parameters and the other will be called by string parameters.

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2. Compile the IDL file of RBR by Orbix IDL compiler to map IDL to Cþþ. Object Skeleton code and Client Stub code are generated. 3. Implementing the IDL Interface. Define a Cþþ class that inherits from the generated class and implement the abstract member functions of this class. Here legacy functions of THCAPP-FS related to reasoning are reused. 4. Write a server program that creates an instance of the implementation class. Call CORBA::BOA:: impl_is_ready( ) to make the object available to clients. 5. Write a client application program that accesses implementation objects through IDL interfaces. 6. Compile the server program and client program, and register the server in the implementation repository so that the OrbixWeb can launch this server automatically when it is invoked. The client can be developed with traditional GUI (Graphical User Interface) or novel web-based interface. Figure 10 shows an example that the machining method selection in CAPP is implemented as a JavaApplet which can access the remote RBR objects.

8. E-DREAM Prototype Implementation Based on the theory and methodology above and using web programming technologies, a prototype of E-DREAM platform has been developed by the Institute of Manufacturing Engineering at Tsinghua University. The prototype architecture is shown in Figure 11. The E-DREAM platform is built on information communication network based on Internet and TCP/IP protocol. The Microsoft IIS (Internet Information Server) is used to be in charge of information processing including information query, resource apply, information exchange, etc. The OrbixWeb is used to support the software resource wrapping and interoperation. Users can use Web browsers such as Netscape or Microsoft IE (Internet Explorer) to enter E-DREAM homepage via a URL address (http:// e-dream.pim.tsinghua.edu.cn). If a user has registered on the E-DREAM platform, he/she can download his/ her own personal working area (or working space) by submitting username and password. The IIS server will automatically distinguish the user roles and send back the corresponding web page to the client user. Figure 12 shows a web page from which the user ‘‘tangdb’’ can know that his resource configuration has been undated, he has a new message from other members, and he has no new task. Figure 12 also depicts the subjection relationship such as this user is the team supervisor of the product design team in project1; he wishes to join in the product data management team in project2 and is


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Figure 10. Machining method selection using RBR.

E-DREAM Platform

Product Design

Personal Workarea

Mould Design

Personal Workarea Personal Workarea

Manfacturing Planning Project Management

Personal Workarea Information Sharing Communication Resource Configuration

Information Query Resource Apply

IIS Server

Information Exchange ...... Resource Wrapping Resource Operation

ODBC Driver

SQL Database CORBA OrbixWeb

Object Server

...... Internet/CORBA

Figure 11. The E-DREAM prototype architecture.

waiting for approval. If the user ‘‘tangdb’’ clicks the active pointer ‘‘management’’, he will enter the Web page to execute the team management function involving approval, dismissal, stopping, and enabling (see Figure 13). Please note that stopping refers to depriving a member’s team rights such as information and resource sharing, but he/she can obtain the team rights again when the team supervisor performs the enabling function for him/her. If the user clicks the active pointer ‘‘sign in’’ in Figure 12, he/she will enter into the corresponding team working space, accessing some shared information, interacting as well as cooperating

with other members. On the message board, a user can send messages to his/her team members and receive messages from them. Figure 14 shows a message-sending interface in which the user can send a message to all team members or some of them. In the resource configuration container, a user sends resource subscription to the team supervisor, and he/she can operate the resource if the servicing status is ‘‘approved’’. Figure 15 illustrates that a user has just obtained the access right to operate the remote software tool entitled ‘‘milling process simulation’’. In virtual enterprise, the geometrically distributed partners are responsible for



Figure 12. A corresponding working environment for a general user.

Figure 13. A team management web page. Downloaded from http://cer.sagepub.com at PENNSYLVANIA STATE UNIV on April 14, 2008 © 2002 SAGE Publications. All rights reserved. Not for commercial use or unauthorized distribution.

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Figure 14. A message sending interface.

developing a shared customized product, thus the remote product model viewing is also important. In E-DREAM, through data management, the user can check-out the shared VRML (virtual reality modeling language) based product model according to his/her privilege level, and implement it as a communication and visualization medium for evaluation of detailed designs (see Figure 16).

9. E-DREAM and Concurrent Engineering The intense global competition and challenges have constantly forced manufacturing industries to consider various new product design, manufacture, and management strategies. Concurrent engineering (CE) is increasingly being used in manufacturing firms. Many research projects have started to focus on the concurrent product design and intelligent decision support in earlier product design stages to fill the gap between the design and other downstream product development processes [24,25]. Sohlenius considers that CE is a way of working where the various engineering activities are integrated and performed, as much as possible, in parallel than in sequence [26]. Vernadat identifies carefully planned teamwork and coordination parallelization of design and engineering work as the two key issues of CE [27]. Prasad points out the importance of product life cycle,

and information exchangeability among cooperating enterprises in concurrent engineering project [28]. For virtual enterprise, several partner companies are creating interdisciplinary CE teams to collaborate on product development projects from dispersed locations, and concurrent product development involves the interaction within and between diverse cross-functional teams of individuals who may be scattered over a wide geographic range. The problems these partner companies face stem from such dimensions [22,29]: (1) incompatible tools and heterogeneous computing platforms for creating and using information; (2) inadequate and inconsistent protection of proprietary information; (3) diversified geographic and demographic information distribution and control; (4) remote coordination, communication, and coordination. Unlike traditional concurrent design, the product development in virtual enterprise requires a virtual concurrent engineering environment. However, there is no platform or system available that can be directly used to support the concurrent design and manufacturing process among different branches or partners that may be globally distributed [30]. E-DREAM, a WWW-based virtual platform, can meet the needs of virtual concurrent engineering environment because of such reasons: (1) By developing a WWW-based product development platform that integrates various technologies, a designer can simulate and virtually observe the downstream



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Figure 15. Resource configuration and operation.

processes for a possible product design on a desktop computer. Thus, the WWW-based integrated product development platform can help the designer to understand the downstream process requirements and design a product correctly in the first instance. (2) Next, the distributed information management mechanism and various information sharing levels ensure that the right information is quickly provided to the right place, at the right time, in the right formats, and enable applications to access and manipulate multiple databases simultaneously. By supporting this capability, the integration of information across enterprises becomes possible. (3) Using CORBA technology, typical CE tools for QFD, DFMA, FEMA, etc. can be wrapped

and performed in the distributed cooperative sites on different computing platforms. (4) The flexible architecture can allow E-DREAM to be configured and expanded according to the requirements of the whole product life cycle. 10. Conclusions In the emerging agile manufacturing industry, a company needs to have a flexible and dynamic environment to cooperate with other companies and form virtual enterprises to produce customized products in time. According to the functional requirements of virtual agile manufacturing, a pragmatic Web-based


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Figure 16. VRML-based product model viewing.

platform entitled ‘‘E-DREAM’’ has been developed. Our main contributions include the following: 1. Analyzing the relationship among real enterprise, virtualized enterprise, and virtual enterprise based on the mapping function. 2. Proposing the E-DREAM architecture which can meet the needs of cooperation, collaboration, and flexibility; providing the E-DREAM global model consisting of four sub-models: virtual working environment, virtualized resources, virtual process, and distributed information, and giving the relationship among them using UML modeling method. 3. Classifying the information into five types (private information, public information, information for some team members, exchanging information, and interoperable information); dividing the information interaction into browsing, exchanging, half-interoperating, and interoperating; and providing a distributed information management approach that supports the practice of virtual enterprising and thus helps achieve the goals of information sharing and interoperability. 4. Interpreting the role and working space management that the access visibility level is dependent on the role that an agile partner plays in a VE. 5. Using CORBA based method to wrap the software resources, solving the problem of communication programs written in different programming lan-

guages and running on different operating systems, and making the remote software tools interoperable. 6. Conducting the implementation of the E-DREAM prototype using Web-based technology. Through the E-DREAM architecture development and prototype system implementation, we have come up with a thorough approach for building virtual enterprises. Having mentioned some contributions of this work, it is worth pointing out the limitations and future research work. As we know, cooperation in virtual enterprises involves information and resource sharing, communication, relationships between different roles (such as administrator/worker or producer/consumer), and collaborative activities. A business process (BP) executed by a virtual enterprise is composed of distributed activities assigned to distributed agile partners. The coordination of these distributed activities is essential for effective cooperation in virtual enterprises. Thus, implementation of a strong mechanism to support multi-level cooperation coordination among different VE partners or roles is also significant for virtual enterprising. For example, the global VE cooperation coordination may be different from virtual team cooperation coordination. Our next step is to carry out the cooperation coordination with workflow management and enhance the capability of E-DREAM for virtual agile manufacturing.



Acknowledgment The work in this paper was supported by China Natural Science Foundation Research Project under the grant No.59889504 and the 985 project of Tsinghua University. The authors are grateful to the anonymous referees for the constructive comments on the original manuscript. The authors also appreciate the financial support of City University of Hong Kong.

References 1. Song, L. and Nagi, R. (1997). Design and Implementation of a Virtual Information System for Agile Manufacturing, IIE Transactions, 29: 839–857. 2. Cheng, K., Pan, P.Y., and Harrison, D.K. (2001). Webbased Design and Manufacturing Support Systems: Implementation Perspectives, International Journal of Computer Integrated Manufacturing, 14(1): 14–27. 3. Qiang, L., Zhang Y.F., and Nee, A.Y.C. (2001). A Distributed and Collaborative Concurrent Product Design System Through the WWW/Internet, International Journal of Advanced Manufacturing Technology, 17: 315–322. 4. Huang, G.Q., Lee, S.W., and Mak, K.L. (1999). Webbased Product and Process data Modeling in Concurrent Design for X, Robotics and Computer-Integrated Manufacturing, 15: 53–63 5. Zheng, L., Tang, D., Li, Z., Wang, X., Liu, C., Huang, L., and Yi, H. (2001). Web-based Technologies Enabling Agile Manufacturing. In Jiang, P. (eds) International conference on eCommerce Engineering: New Challenges for Global Manufacturing in the 21st century (ICECE’21). Xi’an, Shaanxi, China, Sept. 2001 (China Machine Press), RID03-09 (in CD-ROM). 6. Eversheim, W. (1996), Prozeßorientierte Unternehmensorganisation: Konzepte und Methoden zur Gestaltung ‘‘schlanker’’ Organisationen (Process-oriented business engineering: Concepts and methods for the design of ‘‘lean’’ organizations). 2nd ed., Springer Verlag, Berlin, Germany. 7. Lim, S.H., Juster, N. and Pennington, A. (1997). An Information Support System for Enterprise Integration, Concurrent Engineering: Research and Applications, 5(1), 13–22. 8. Prasad, B., Wang, F., and Deng, J. (1997). Towards a Computer-Supported Cooperative Environment for Concurrent Engineering, Concurrent Engineering: Research and Applications, 5(3); 233–251. 9. Zhang, L., Chan, S.C.F., Ng, V.T.Y., and Yu, K.M. (2001). Enterprise Virtualisation: Concepts, Methodology, and Implementation, International Journal of Advanced Manufacturing technology, 18; 217–234. 10. Noaker, P.M. (1994). The Search for Agile Manufacturing. Manufacturing Engineering, 113: 40–43. 11. Comerford, R. (1993). The Flexible Factory: Case Study, IEEE Spectrum, 30: 28–29. 12. Goldman, S., and Nagel, R. (1993). Management, Technology and Agility: the Emergence of a New Era in Manufacturing, International Journal of Technology Management, 8(1/2): 18–38.

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13. Gunasekaran, A. (1999). Agile Manufacturing: a Framework for Research and Development, International Journal of Production Economics, 62: 87–105. 14. Quinn, R.D., Causey, G.C. and Sargent, D.M. (1997). An Agile Manufacturing Workcell Design, IIE Transactions, 29: 901–909. 15. Horstmann, P., Bolon, R., Dewey, A., Goldschimdt, A., and Blazjey, A. (1997). Manufacturing Virtual Enterprises Through the Use of the National Industrial Information Infrastructure Protocols (NIIIP), SPIE, 2913: 20–32. 16. Graves, R.J., Agrawal, A., and Haberle, K. (1996). Estimating Tools to Support Multipath Agility in Electric Manufacturing, IEEE Transactions on Components, Packaging, and Manufacturing Technology Part C: Manufacturing, 19(1): 48–56. 17. Garita, C., Afsarmanesh, H. and Hertzberger, L.O. (2001). The PRODENT Cooperative Information Management for Industrial Virtual Enterprises, Journal of Intelligent Manufacturing, 12: 151–170. 18. Sandakly, F., Garcia, J., Ferreira, P. and Poyet, P. (2001). Distributed Shared Memory Infrastructure for Virtual Enterprise in Building and Construction, Journal of Intelligent Manufacturing, 12: 199–212. 19. Zhou, Q., Ristic, M. and Besant, C.B. (2000). An Information Management Architecture for Production Planning in a Virtual Enterprise, International Journal of Advanced Manufacturing Technology, 16: 909–916. 20. Pallot, M. and Sandoval, V. (1998). Concurrent Enterprising: Towards the Concurrent Enterprise in the Era of the Internet and Electric Commerce. Kluwer Academic Publishers, Boston/Dordrecht/London. 21. Chen, Y.-M. and Jan, Y.–D. (2000). Enabling Allied Concurrent Engineering Through Distributed Engineering Information Management, Robotics and Computer Integrated Manufacturing, 16: 9–27. 22. Chen, Y.-M. and Liang, M.-W. (2000). Design and Implementation of a Collaborative Engineering Information System for Allied Concurrent Engineering, International Journal of Computer Integrated manufacturing, 13: 11–30. 23. Li, Z. (1999). Research on CAPP framework system for Concurrent Engineering. Ph. D. dissertation, Tsinghua University, Beijing, China 24. Kusiak, A., (ed.) (1993). Concurrent Engineering: Automation and Tools, and Techniques. Wiley, New York. 25. Prasad, B. (1996). Concurrent Engineering Fundamentals, Vol. 1, Prentice Hall, Englewood Cliffs, New Jersey. 26. Sohlenius, G. (1992). Concurrent Engineering, Annals of the CIRP, 41(2): 645–655. 27. Vernadat, F.B. (1996). Enterprising Modeling and Integration. Chapman & Hall, London. 28. Prasad, B. (1997). Concurrent Engineering Fundamentals, Vol. 2: Integrated Product Development, Prentice Hall PTB, Upper Saddle Saddle River, New Jersey. 29. Sky, W.E.S. and Buchal, R.O. (1997). Modeling and Implementation Concurrent Engineering in a Virtual Collaborative Environment, Concurrent Engineering: Research & Applications, 7(4): 279–289. 30. Xie, S.Q, Tu, P.L., Aitchison, D., Dunlop, R. and Zhou, Z.D. (2001). A WWW-based Integrated Product Development Platform for Sheet Metal Parts Intelligent Concurrent Design and Manufacturing, International Journal Production Research, 39(17): 3829–3852.


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Dunbing Tang

K. S. Chin

Dunbing Tang is a postdoctoral research fellow at the Institute of Manufacturing Engineering (National CIMS Research Centre), Tsinghua University (Beijing). As a Humboldt Research Fellow, he is conducting research at Aachen University of Technology from 2002– 2003. His research interests include CIMS (Computer Integrated Manufacturing Systems), CE (Concurrent Engineering), agile manufacturing, design for manufacturability, web-based design and manufacture, concurrent stamping parts and die development, conceptual product design, and process reengineering. Dr. Tang has published over 40 journal papers in these fields, and his works can be found in academic journals such as Concurrent Engineering: Research and Applications, Computers in Industry, International Journal of Advanced Manufacturing Technology, Journal of Intelligent Manufacturing, Computers & Industrial Engineering.

K. S. Chin is an Associate Professor in the Department of Manufacturing Engineering and Engineering Management, City University of Hong Kong. Before joining the university, Dr. Chin had more than 10 years experience in the manufacturing industry. He is a Chartered Engineer in the UK and a Registered Professional Engineer in Hong Kong. Dr. Chin is a fellow of the Hong Kong Society for Quality, and a senior member of American Society for Quality (ASQ), Institute of Industrial Engineers (IIE) and Society of Manufacturing Engineers (SME), USA. Dr. Chin has published over 80 papers in the fields of product development and management and quality management. His current research interests are new product development strategies in the Internet Age, quality management strategies beyond ISO 9000 for Hong Kong and China, and the use of artificial intelligence technologies in product design.

Li Zheng

Zhizhong Li

Prof. Li Zheng is the executive head of the Department of Industrial Engineering, Tsinghua University. He received his PhD degree in Mechanical Manufacturing from Tsinghua University in 1990. From 1994 to 1996, Prof. Zheng was doing research work in the ME Department of Georgia Institute of Technology as a visiting professor. His current research interests include cutting process modeling and simulation, CIMS (Computer Integrated Manufacturing Systems), and agile manufacturing based on network. Prof. Zheng is a senior member of the Chinese Mechanical Engineering Society.

Dr. Zhizhong Li received his BS degree, MS degree and PhD degree in Manufacturing Engineering and Automation from Tsinghua University, Beijing, China in 1993, 1995 and 1999, respecively. Dr. Li has eight years of teaching and research experience with the Department of Precision Instruments and Mechanology, Tsinghua University and nine years of software development experience under various platforms. Currently, he is at the Department of Precision Instruments and Mechanology, Tsinghua University. His research interests include CAD/CAPP/CAM, cutting process modeling and simulation, geometric modeling, reverse engineering, network enabled manufacturing and artificial intelligence in manufacturing. He is a senior member of the Chinese Mechanical Engineering Society.



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Yulan Liang

Changjian Hu

Yulan Liang is a candidate for MS in Manufacturing and Automation at Tsinghua University, Beijing, China. She received her Bachelor degree in Machine Design and Manufacturing and Automation at Tsinghua University. Her research focuses on the web-based simulation and scheduling arithmetic for the mixed simulation models that include both the continuous subsystems and discrete subsystems.

Changjian Hu is a PhD candidate at the Department of Precision Instruments and Mechanology, Tsinghua University. He received his BE degree from Tsinghua University in 1999. His research interests include manufacturing process management, knowledge management and advanced manufacturing systems assessment.

Xiaojian Jiang Xiaojian Jiang is a graduate student in the Department of Industry Engineering of Tsinghua University. He received his BS in 2000 from the Shanghai Jiao Tong University. His research interest concentrates on database and web technology, distributed object computing, information modeling and network simulation.
