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International Journal of Computer IntegratedManufacturingPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/tcim20

CoDesign Space: a collaborative design support systemin a network environmentLing Tian a , Jizhong Chen a , Qiaoyu Wang a , Wentao Hao a & Bingshu Tong aa Department of Precision Instruments and Mechanology , Tsinghua University , Beijing,100084, ChinaPublished online: 21 Mar 2007.

To cite this article: Ling Tian , Jizhong Chen , Qiaoyu Wang , Wentao Hao & Bingshu Tong (2007) CoDesign Space: acollaborative design support system in a network environment, International Journal of Computer Integrated Manufacturing,20:2-3, 265-279, DOI: 10.1080/09511920601150636

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CoDesign Space: a collaborative design support systemin a network environment

LING TIAN*, JIZHONG CHEN, QIAOYU WANG, WENTAO HAO and BINGSHU TONG

Department of Precision Instruments and Mechanology, Tsinghua University, Beijing 100084, China

In order to satisfy the various applicational requirements in a network environment, a

multi-mode collaborative design method is proposed. Based on XML and VRML

technology, the implement method of product data sharing and integration is also

discussed. A general type net-based collaborative product design support system called

CoDesign Space is designed, and the system architecture and realization method are

presented. The CoDesign Space system has a flexible and extendable three-tier B/S

architecture. Meanwhile, the system can satisfy the requirements of geographically

dispersed collaborative design in many ways by integrating several collaborative design

support tools that can be used independently.

Keywords: Collaborative design; Design support system; Product data management;

Conflict management

1. Introduction

Due to increasingly intense market competition, and

especially to the fact that the design of many complicated

products must be completed through the collaborative

work of geographically dispersed designers, there is an

urgent demand for companies and organizations to provide

a net-based collaborative design environment with which

they can perform geographically and professionally un-

limited collaborative product development in order to

develop a product that is more competitive and that meets

the customers’ demand. Hence, the collaborative design in

the network environment comes into being, and the rapid

development of computer technology provides the neces-

sary condition for its development and application.

The net-based collaborative product design is a method

whereby geographically dispersed designers can perform

their design work concurrently, interactively and collabora-

tively based on the computers in a WAN environment. The

product is designed simultaneously by many designers, who

only need to perform their own pieces of work in order to

complete the whole task (Kvan 2000, Tian 2002). The most

important characteristic is that the product design is

performed by geographically dispersed designers. Designers

can cooperate by network and share information, process,

and design resources. Collaborative designers can resolve

tasks, design project discussion, design results checking and

modification, and detect and resolve conflict, thus enabling

a distributed product design to perform concurrently. This

method can significantly shorten the product design cycle,

optimize the performance of products, lower the product

development cost, and increase the ability of individualized

development by performing net-based collaborative design

(Saad and Maher 1996, Regli 1997, Xu and Liu 2003).

In the 1990s, Cutkosky and Toye (Cutkosky et al. 1993,

Toye et al. 1993) from Stanford first started researching

collaborative design. With the development of computer

and network technology, the research gradually broadened

and deepened. The related work concentrates primarily on

the following aspects: collaborative design based on CAD,

collaborative design based on the Internet, the sharing and

visualization of product information, collaborative design

based on Agent and conflict management, etc.

As the traditional CAD tools are designed for single-

computer users, in order to support collaborative design we

need to develop a corresponding interface for integration to

establish the geographically dispersed cooperative mechan-

ism. The original company SDRC encapsulates the core

*Corresponding author. Email: tianling@mail.tsinghua.edu.cn

International Journal of Computer Integrated Manufacturing, Vol. 20, Nos. 2 – 3, March –May 2007, 265 – 279

International Journal of Computer Integrated ManufacturingISSN 0951-192X print/ISSN 1362-3052 online ª 2007 Taylor & Francis

http://www.tandf.co.uk/journalsDOI: 10.1080/09511920601150636

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part of its I-DEAS based on CORBA, forming the Open

I-DEAS, which supports long-distance transfer through a

network.

The net-based product collaborative development is a

synthetic process of receiving customers’ requirements

through the network, organizing many collaborative

product development teams and using professional knowl-

edge to make decisions collaboratively and to export

product data. Typical research projects include the Internet

laboratory established by the Industry Engineering depart-

ment of Iowa University in the United States (Kim et al.

1996) and the Cybercut system developed by California-

Berkeley University in the United States (Smith and Wright

1996).

The sharing and visualization of product information are

the foundation of Internet-based collaborative design and

manufacturing (Zhang et al. 2004). Hardwick and Spooner

(1995) presented a virtual manufacture enterprise-oriented

information foundation framework to support virtual

enterprise working collaboratively. Ando et al. (1998),

Kan et al. (2001), and Craig and Zimring (2002) have

researched collaborative design, and their research is based

on the VRML model.

The Agent encapsulates different levels of knowledge in

the problem region, enabling it to perform assigned tasks.

Collaborative work can be realized by the communication

and management mechanism between Agents (Wallis et al.

1998, Anumba et al. 2001). Cutkosky, etc. of Stanford

University developed an Agent-based distributed integrated

concurrent engineering experiment system called PACT

(Cutkosky et al. 1993).

In the collaboration process, conflicts are unavoidable,

and how they are detected and resolved is very important

for completing collaborative design work. Klein (1991),

Lottaz et al. (2000), and Taratoukhine (2002) have all

studied conflict management. Victor Taratoukhine pre-

sented the current conflict-management technology in the

computer-supported collaborative work environment and

presented a conflict-management approach called IDMC,

which includes a process model and a structure model

based on a multi-Agent framework. Mark Klein proposed

an effective conflict-resolving approach for collaborative

design. According to the theories of CSP, C. Lottaz

proposed the conflict negotiation approach based on

constraints.

Many universities and research institutes in China have

done a great deal of research on collaborative design. The

Project ‘Concurrent Engineering’ supported by the Na-

tional High- Tech R&D Programme for CIMS includes the

research on collaborative design, which was undertaken by

Tsinghua University, Beijing University of Aeronautics &

Astronautics, Shanghai Jiao Tong University, Huazhong

University of Science & Technology, and the Second

Academy of China Aerospace Science & Industry Corp

(Xiong et al. 1996). In 1997, Rongbin Li of Hong Kong

University and Shu Zhang of Tongji University proposed a

CSCD model that is based on multi-agent technology and

that can support collaborative work through information

interchange among agents (Li 1997). Professor Yushun Fan

of Tsinghua University provided the system architecture

for a manufacturing network integration platform (MNIP)

based on the multi-agent system’s control framework and

support tools. Its objective was to construct a manufactur-

ing network system to support commerce collaboration,

design collaboration, manufacturing collaboration, and

supply-chain collaboration among enterprises using ad-

vanced network technologies, thus enhancing the total

competition of industrial chain and manufacturing enter-

prises (Fan and Li 2003). Moreover, Huazhong University

of Science and Technology (Yang 2000), Xi’an Jiaotong

University (Xie 1998), and other research institutes have

also done some research on this subject.

From the present research status discussed above,

research on collaborative design abroad began very early,

and many research results that also achieved good effects

have already been applied in practice. Some research has

also recently been done in China, but most of it stresses the

feasibility analysis and the construction of a theoretical

model for collaborative design, the research of enabled

technologies required by the collaborative design environ-

ment, etc. The research seldom studied further problems in

the process of collaboration design according to the real

requirements of collaborative product design in network

environment, such as the collaborative design mode, the

product information-sharing mechanism in a network

environment, conflict detection and resolution, the con-

struction of a net-based collaborative design support

system, and the organization of different assistant software

tools in net-based collaborative design.

Based on the research and the problems in practice

discussed above, the paper mainly researches the following:

1. Based on the systemic research on the application

background of net-based collaborative product de-

sign, this paper proposes a multi-mode collaborative

design method for net-based collaborative design

and defines four collaborative design modes. This is

the precondition for building net-based collaborative

product design and also for system function and

architecture design.

2. In the process of net-based collaborative design, the

shared product data have characteristics of distribu-

tion and heterogeneity. This paper resolves the

sharing and integration problem of heterogeneous

product structure information and product model

information by XML and VRML technologies.

3. According to actual requirements of collaborative

product design in a network environment, a

266 L. Tian et al.

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Web-based collaborative design support system

(CoDesign Space) was designed and implemented,

consisting of a collaborative information manage-

ment platform and a group of independent colla-

borative design support tools. It has an open and

flexible structure and can support geographically

dispersed designers in designing and developing

products collaboratively in a variety of ways, such

as product sharing, information management, col-

laborative product viewing, conflict detection and

resolution, etc.

2. Multi-mode collaborative design method

The product design is an all-embracing conception. Because

of the diversity of the world, the aims of product design

vary greatly, and the design modes are different. Consider-

ing factors such as cost, life cycle, and quality, different

types of products are designed in different methods.

Accordingly, the net-based product design must be multi-

mode. Some common collaborative design modes are

discussed below. They are the basis of function design

and structure design of CoDesign Space system. CoDesign

Space has a flexible and open structure so that it can be

adapted to modes available now and in the future.

2.1. Collaborative design mode based on task management

In this mode, the process of each sub-task is controlled

coordinatively, ensuring that the whole task of collabora-

tive design is finished successfully. This mode needs a task-

management system with powerful functions that can break

down tasks, define sub-tasks, manage constraints, and

control task processes.

In the collaborative design mode based on task manage-

ment, a whole task is broken down into several sub-tasks.

The constraint network is defined by the relationships of

each sub-task process, and the whole collaborative design is

implemented according to the management and control of

processes. Great attention should be paid to the control of

the whole project process; finishing each sub-task on time is

the primary problem. This control method, with process

management as its core, is mainly used to resolve standard

or common design problems. The cell functions of the

design are usually clear, and priority is given to task

management.

2.2. Collaborative design mode based on conflict

resolution

Collaborative design mode based on conflict resolution is

an approach that totally coordinates and manages the

process of collaborative design by detecting and resolving

the conflicts in all steps. In the product-design process,

conflicts may occur in every step and on each organiza-

tional level. To some extent, the product development is a

process of conflict detection and resolution. Although

conflicts will negatively influence the design process to a

certain degree, they can also promote the design process.

As each conflict is resolved, a much more optimized design

result will be obtained finally.

A conflict-management system is necessary in the

collaborative design mode based on conflict resolution.

According to the requirements, designers can define the

constraints of each sub-task, construct a whole constraint

network, and detect conflicts based on the constraint

network. The conflict resolution system can resolve con-

flicts automatically; if it does not work, a discussion

and a decision are needed. The collaborative design mode

based on conflict management is especially well suited to

resolving difficult problems in the design process such as

scheme design, conceptual modelling, and partial detail

design.

2.3. Collaborative design mode based on product

information sharing

This mode is a design method that allows designers of each

sub-task to finish tasks interactively by sharing product

design information in a collaborative virtual space based on

WAN (wide area net). In order to allow each designer to

share design information adequately, a product-design

information-sharing system should be built in this mode,

and some collaborative communication tools are necessary

to ensure that information can reach the particular designer

correctly and on time.

According to the characteristics of differently designed

objects, designers use different information-sharing systems

to finish their tasks in the collaborative design mode based

on product information sharing. In the phase of conceptual

design, a heterogeneous product structure information-

sharing system can integrate the information from different

management systems of collaborative design teams. In this

sharing system, designers can implement design based on

product structure trees. In the phases of structure design

and detail design, a collaborative virtual modelling system

can integrate different product models from heterogeneous

CAD systems based on VRML format. Designers can

detect the interference and research the product assembly

problem based on product models, and they can also view

and mark the models with this system.

This collaborative design mode based on product

structure information sharing is especially well suited to

the product designs, most of which are mechanical struc-

tures. Especially in the phases of structure design and detail

design, this mode is very useful for the common design,

distortion design, and improving design when the tasks are

plainly broken down, and product structure is clear.

CoDesign Space 267

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2.4. Collaborative design mode for product innovation

design

The collaborative design mode for product innovation

design supports knowledge-based innovative design. The

innovative degree of a product directly affects its market

competitiveness. In an era of knowledge explosion, the

collaborative design based on WAN is an effective method

for creating innovative products. The inherited knowledge

can be obtained from a knowledge repository when the

innovative knowledge is not available or not clearly

available, and it can be obtained through iterative research,

discussion, and communication in the process of colla-

borative design. Therefore, a knowledge management and

acquisition system should support the acquisition of

inherited knowledge. Meanwhile, a support system that

allows the designers to collaboratively create knowledge is

necessary.

In the collaborative design system for product innova-

tion, designers first retrieve existing knowledge through a

knowledge-management system when designing a new

product. If the system cannot satisfy requirements,

designers can exchange their design ideas through the

intelligent collaborative design tool to find a new approach

to resolving the problem. On the other hand, the knowledge

repository is open so new knowledge can be added, and the

repository can be expanded continuously.

This mode works well for the design of new products that

do not yet exist. The support environment serves the

intelligent collaboration of designers who lie at the very

centre of innovative design, and this emphasizes the

foremost thoughts of the concept designer.

3. Product information sharing and integration

Product information can be divided into two parts: product

model information and product structure information, as

shown in figure 1.

3.1. Product model information integrating

and sharing

Product model information includes geometry information,

process information, and constraint information of product

components. All information is created by the CAD

system, and different formats are used by different CAD

systems to store the information. For the integrating

problem of heterogeneous CAD systems, two methods

are frequently used: STEP-based information integrating

and special point-to-point integrating.

For the net-based collaborative design, the copartners

are temporarily united, and the special point-to-point

integrating method cannot satisfy the requirements.

Furthermore, limited by the bandwidth of the net, the

STEP-based CAD model files, which are often very large,

are not fit to transfer on the Internet.

VRML is a language that describes the 3D entity model

and provides a 3D environment with depth of field and

stereoscopic sensation. This makes it possible to implement

3D model-based visual collaboration, and it becomes a

feasible method to support collaborative design. As a

common graphic format, VRML is supported by many

CAD companies. Almost all the popular CAD systems can

export 3D and 2D VRML graphic files, but much design

information will be lost, and only graphic information is

saved when CAD models are exported in VRML. If you

import the VRML model into the CAD system again after

it has been modified, it will not be recovered. For this

reason, when they are designing via the Internet, designers

can communicate adequately with each other through the

3D VRML model and modify the model in the CAD

system in which it was created. The rule is that many

persons are involved in the discussion of a model and can

reach a final modification scheme, but only the model

designer has the right modify it. This is the same as the

product design method for most companies. A product

model information sharing based on the VRML model (as

shown in figure 2) is discussed in this paper.

A VRML-based product model information-sharing

system is needed to provide model viewing and virtual

assembling functions. Geographically dispersed designers

can collaboratively view VRML geometry models in the

sharing system as if they were all in front of one computer.

They can also virtually assemble products, check the

assembling interference, and plan the assembly path on

the basis of the geometry models. The assembly model from

a certain CAD system can be disassembled, and its

assembly path can also be planned in the system. At the

same time, the marking tool can be used to mark the model

in this system. The process information and constraint

Figure 1. Product-design information.

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information from CAD systems are recorded in a file and

related to the product structure tree. According to the

information, conflicts can be detected and resolved through

conflict-detection and constraint-management tools pro-

vided by this system.

For collaborative design, geographically dispersed CAD

systems can transform the geometry model into the VRML

model and send it into a sharing system via the Internet. If

the model needs to be modified, the modification sugges-

tions will be sent to the corresponding CAD system, and

the model will be modified in a local environment according

to these suggestions.

In this information-sharing method, VRML files make it

possible for the geometry models from heterogeneous CAD

systems to be viewed in a sharing environment, but the

detail designs such as modification will be done in an

individual CAD system. This makes it easy to build the

sharing system. The design flow is the same as that of a

non-computer environment and is consistent with the

thinking habits of man. This makes the net-based

collaborative design a practicable design approach because

it ensures that the information is shared, and it avoids

many difficult problems in heterogeneous CAD systems

integration.

3.2. Product structure information integrating

and sharing

Product structure information is managed in PDM systems.

Different companies in temporary allied collaborative

design may use different PDM systems, and finding a

way to share the product structure information from

heterogeneous PDM systems becomes a difficult problem.

A XML-based product-structure information-integrating

and sharing method (as shown in figure 3) is discussed in

this paper.

First, a product-structure information-sharing model is

created, equivalent to making a protocol for implementing

product-structure information sharing. Information-

sharing models will be defined by DTD models according

to the protocol. Then, an XML-based collaborative

product-information management system will be built to

provide functions such as shared information management,

product-structure viewing, and constraints synthesizing,

and the system also provides the integrating interfaces

based on the information-sharing mode.

In this product-structure information-sharing system, the

product-structure information (XML files) from different

PDM systems is integrated into the collaborative product-

information management system through the integrating

interfaces, and it becomes shared information. The system

provides visual interfaces for users and provides XML files

for cooperators. The users from different places can view

the product structure trees corresponding to the shared

information, search related information through the trees,

build a constraint network, and implement collaborative

designs. At the same time, the management system can

transform the product-structure information produced by

PDM 1 (in figure 3) into shared information and transfer

the shared information to PDM 2 (in figure 3). The

integrating interface of PDM 2 will add the received

information to PDM 2. This method is quite sufficient to

integrate product-structure information from different

PDM systems.

Figure 2. Product-model information sharing.

Figure 3. XML-based product structure integrating and

sharing method.

CoDesign Space 269

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4. Net-based collaborative design support system:

CoDesign Space

Based on a common data format, a net-based collaborative

product design-support system (CoDesign Space) was

developed entirely from the bottom and did not depend

on any commercial CAD system. This system includes a

collaborative information-management platform and a

group of collaborative tools and applications for product

development, and it can meet the requirement of multi-

mode geographically dispersed collaborative design in

different ways. The system architecture of CoDesign Space

is shown in figure 4.

The bottom tiers of CoDesign Space system are the

network/database tier and the application protocol tier,

which adopt an Internet network and a SQL Server 2000

database management system. The application protocol tier

includes STEP, XML, VRML, HTTP, etc. CoDesign Space

supports heterogeneous information integration and shar-

ing by using STEP, XML, and VRML technologies.

The system service tier and the application service tier are

above the bottom tier of this system. The system service tier

manages the foundational data of the whole system and

provides basic control and collaborative functions. The

application service tier consists of a group of application

services (system management service, product structure

management service, document management service, and

resource management service) and a group of collaborative

tools (e-mail service). The application service tier can be

extended according to practical requirements, and colla-

borative tools can be used as a separate system indepen-

dently, providing a good foundation for the flexibility of

the CoDesign Space system.

All the tiers above construct the integration framework

of the collaborative design support system. Programmers

can integrate many application systems according to

Figure 4. System architecture of CoDesign Space.

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requirements: for instance, a VRML-based virtual assem-

bly system, XML-based product structure information-

sharing system, collaborative task plan and management

system, conflict detection and negotiation system, knowl-

edge management and intelligent collaborative system, etc.

These application systems can be integrated into CoDesign

Space closely, while at the same time they can also be used

separately. CoDesign Space is flexible and extendable,

supporting multi-mode collaborative design because of the

independence of these collaborative tools and application

systems.

5. System realization

In order to satisfy the requirements of net-based colla-

borative design, we designed and realized a collaborative

virtual assembly tool, a collaborative viewing and markup

tool, a conflict-management tool, a collaborative product-

configuration tool, a visual document-management tool, a

collaborative task-management tool, a collaborative

design-resource repository management tool, and other

collaborative design-support tools. These tools can be

integrated and extended easily, and can also be used as a

separate system.

5.1. Collaborative virtual assembly

The CoDesign Space is a general type collaborative

platform, which needs to perform collaborative design

based on a general format. The collaborative virtual

assembly tool is a very important tool for this platform.

Via-VRML takes VRML (an Internet-enabled data for-

mat) as its carrier, and the VRML model can be exported

from the CAD models from different platforms, especially

the CAD models of diverse places and platforms. It realizes

single or multi-person (including experts, designers, sales,

and customers) to collaboratively process the pre-assembly

of product in order to check the assembly ability or to

collaboratively evaluate the product visually. On the basis

of an effective product VRML model, users collaboratively

complete the assembly planning layout, such as assembly

sequence layout and assembly path layout. If there is any

interference between the parts, the system provides the

function of establishing a collaborative team. Related

members can discuss problems and offer modifying

suggestions online in the network environment. Further-

more, the system can work in single-computer mode or

collaborative team mode, realizing the product planning

layout. Figure 5 shows the system construction of the Via-

VRML tool, and figure 6 shows the interface.

This system aims at resolving the problem of direct pre-

assembly of cross-platform CAD and makes it possible for

related members in diverse locations to discuss problems

directly. After converting different models to VRML

format, it can perform a real-time assembly planning

layout and assembly ability examination. Its main func-

tions are as follows:

1. Product pre-assembly. Collaborative members per-

form the product pre-assembly based on VRML,

examining the assembly ability of parts from

different task teams.

2. Assembly sequence layout. For the existing CAD

models, by searching the assembly method between

the parts, the sequence of product can be built based

on assembly ‘abutment’ characteristics.

3. Assembly path layout. In the form of visualization

and through human–computer interaction, after

interference detection designers can determine the

feasible assembly path and imbed the results into a

VRML model file, which can be displayed on the

Web Browser. Due to limited bandwidth, the solid

models used by the existing commercial CAD

Figure 5. System construction of Via-VRML system.

Figure 6. Interface for the Via-VRML tool.

CoDesign Space 271

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systems are not suitable for collaborative design in

the network environment.

The VRML model is used as a kind of general expression

format that is suitable for transfer on the Internet. It is

widely supported by many CAD software companies. At

present, the main CAD software provides the 2D and 3D

VRML format export, which is suited to distributed

VRML-based collaborative design; however, when the

CAD system generates a VRML model, a large amount

of information is lost, making it impossible to perform any

deep-level operation for the model except to browse it on

the Web.

After studying the VRML model, we realized the

operation of the VRML model and developed a VRML-

based collaborative virtual assembly system: Via-VRML.

In support of VRML Automation Object Model for

Cortona ActiveX Control, it imports VRML models from

different CAD systems and realizes parts pre-assembly by

obtaining the information of VRML scene node (such as

position and orientation information). Moreover, it realizes

functions such as collaboratively viewing VRML models in

diverse locations, collaborative product pre-assembly,

assembly simulating, assembly layout, collision interference

detection, etc. It also supports collaboration in real time

online, providing an effective tool for collaborative design.

Via-VRML is a convenient and vivid independent work

environment developed completely from the bottom, and it

does not depend on any existing CAD system. It supports

geographically dispersed users and heterogeneous CAD

system performing virtual design of product collaboratively

on the Internet. This tool is encapsulated as an ActiveX

control and integrated with the CoDesign Space system.

5.2. Collaborative viewing and markup

For product design, the tool supporting geographically

dispersed collaborative communication based on a 2D or

3D model plays an important role. Geographically

dispersed designers can find design problems as quickly as

possible by viewing and analysing 2D/3D models on the

Internet; they then propose change suggestions, which can

reduce the time required for redesign and quicken product

development. At present, several common viewing and

mark-up tools exist, such as Volo View Express of

Autodesk Company, ProductVision of UG Company, 3D

View of Actify Company, and dV/PoductView of PTC

Company. Most of these tools do not support real-time

collaborative viewing and markup function. Some of them

do not support the synchronization of markup information

with the model despite supporting the viewing function.

Considering these, we designed and developed a tool for

collaborative viewing and markup of a 2D drawing/

document and a 3D VRML model. This tool supports

collaborative communication among geographically dis-

persed design experts in a sharing space; designers can

express their suggestions on the model. This real-time

communication approach can enhance the efficiency of

communication and reduce mistakes among collaborative

communicators. In the mean time, the tool also supports

collaborative product innovation.

The following are the main functions of the collaborative

viewing and markup tool:

1. Viewing a 2D/3D model. The tool supports viewing

multi-format documents generated by CAD soft-

ware or word-processing software, such as typical

2D documents: DWG, DXF, DGN, PS, etc.; text

documents: DOC, PPT, XLS, PDF, etc.; 3D models:

VRML or other format models created by UG,

Solidworks, Proe, etc.

2. Marking up a 2D/3D document. Design experts can

express their viewpoints by marking up a 2D/3D

document.

3. Viewing markup information. Design experts can

learn the viewpoints of other experts by viewing their

markup information.

4. Collaborative viewing. Geographically dispersed

designers can collaboratively view the same 2D/3D

document and communicate with each other online.

5. Collaborative markup. Geographically dispersed

designers can mark up and discuss the design

problems with each other on the same 2D/3D

document. Designers express their suggestions

through marking up the document and can know

the thoughts of other designers on the basis of their

markup information on the same document. In this

way, the design problems can be found and resolved

in time, thus improving the efficiency of product

design and enhancing the quality of product.

The collaborative viewing and markup tool was devel-

oped by VCþþ and deployed in ActiveX control. It can

also be easily integrated into other application systems. The

interface of this tool is shown in figure 7.

5.3. Conflict management

Net-based collaborative design supports multi-subject and

multi-area workgroups to cooperate synchronously or

asynchronously in different locations, and in this way

designers can accomplish product design and development

by working together. Many kinds of inter-relationships exist

among parts in collaborative development, and the con-

straint network composed of these relationships controls the

whole collaborative design process. In the collaborative

design process of a complicated product, conflicts in the

constraint network are inevitable because of the discrepancy

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of design targets, viewpoints, design environment, and

knowledge level. Through managing the constraint network

in collaborative design, we can detect conflicts and resolve

them. This is helpful to coordinating and managing each

design stage, and, thus, it can ensure that the collaborative

design will work properly.

Based on the hierarchical, distributed, and concurrent

characteristics of collaborative design, we developed a

constraint-management tool and realized the management

of the constraint network and the functions of conflict

detection and resolution. This tool can enable the project

partners to manage the constraint object hierarchically, con-

currently, and distributed in a shared information space,

thereby improving the efficiency of collaborative design.

5.3.1. Constraint-Satisfaction Problem theory and interval-

propagation algorithm. The conflict-management tool

adopts the Constraint-Satisfaction Problem (CSP) theory

to detect explicit conflict. A CSP of a project design consists

of the following (Lottaz et al. 2000, Bartak 2003):

. X¼ {X1 , . . . ,Xn}, Xi is the variable expressing

product property;

. D¼ {D1 , . . . ,Dn}, each Xi has its domain Di . D need

not be a set of consecutive integers, even need not be

numeric;

. C¼ {C1 , . . . ,Cm}, each constraint is composed of

two parts:

1. variable set V(Ci)¼ {Xi1 , . . . ,Xip}, p5 n;

2. relationship R(Ci)¼R(Xi1, . . . ,Xip)� Di16 � � �6Dip.

Therefore, all solutions to constraint can be expressed as

follows:

KðZÞ ¼fðX1 ¼ x1; . . . ;Xn ¼ xnÞj 8Ci;

PVðCiÞRðCÞ � RðCiÞg ð1Þ

where PV(Ci)R(C) is the projection of variable set V(Ci) on

relationship set R(C), and R(C) expresses all the constraints

of constraint network.

The interval-propagation algorithm computes the variety

of variable domain confined by the constraints. Its goal is

to compute the feasible solution domain D0 of each design

variable Xi(1� i� n) confined by the constraint set C, D0 �D. For constraint R(Ci)¼R(Xi1, Xi2 , . . . ,Xip), if the former

definition domain of Xi1 is Di1, the new definition domain

of Xi1 confined by constraint R(Ci) is: Di10¼{f71([R(Ci)])

jXi1}\Di1, where f71([R(Ci)])jXi1 is the feasible domain

gained by anti-resolving the constraint R(Ci) according to

the interval-propagation algorithm. Applying the for-

mula above to each variable in a design-constraint-

satisfaction problem given by equation (1), their feasible

domains can be computed. If the feasible domain D0 of

one or more design variables is null, conflicts exist in the

design.

The detail algorithm is as follows (Hyvonen 1992):

1. Initialization

Variable domain set: D¼ {D1, D2 , . . . ,Dn}

Initial resolution function set:

FI¼{Fij j i¼ 1, 2, . . . ,m; j¼ 1, 2, . . . , p}

Resolution function set: FS¼FI2. for (FS 6¼ F)

{

Take Fij from FS, Fij 2 FS;

Compute the feasible domain Dk0 of variable

Xk(k¼1, 2, . . . , n) using the interval-propagation

algorithm;

if (Dk0 �Dk) then

Delete Fij from FS

else

{

Dk00 ¼Dk

0 \Dk;

if (Dk00 ¼F) then

Show conflict information and exit;

else Dk¼Dk00

}

}

5.3.2. Function design and realization of conflict-

management tool. The conflict-management tool includes

constraint-network-management and conflict management.

The constraint network management module supports the

constraint-variable-management function and constraint

Figure 7. Interface for the collaborative viewing and

markup tool.

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expression-management function, while the conflict man-

agement module has a constraint-verification function (to

detect explicit conflict), conflict-detection function (to

detect implicit conflict), and conflict-resolution function.

The function structure is shown in figure 8.

1. Constraint-network management. According to

their own design assignment, the project partner

creates and maintains design variables and a

constraint network based on product structure. In

the mean time, the system records the change history

of variables and constraints. Thus, it can provide the

basis for system backtracking.

2. Conflict finding. This module includes a constraint-

verification function and conflict-detection function.

Constraint verification supports explicit conflict

detection by a conflict-detection approach based on

the real value, and its historical information is

recorded by the system. Conflict detection can detect

implicit conflict in a local or global constraint

network with a constraint propagation algorithm.

The results of detection can be saved in the system so

that the designers can resolve the conflict whenever

they want to.

3. Conflict resolution. The designers can get sugges-

tions for conflict resolution by choosing one or

several of the following approaches: sequential

backtracking strategy, correlative control-guide

backtracking strategy, and constraint relaxation or

mediator strategy. By referring to these suggestions,

they can negotiate with other designers and finally

achieve the purpose of conflict resolution.

According to the approach of hierarchical constraint

network management, CSP theory, conflict detection, and

conflict resolution strategies, we developed a constraint-

based conflict management tool by Web technology. Its

interface is shown in figure 9.

5.4. Collaborative product configuration

Product configuration management can be considered a

snapshot of product structure, related document data, integ-

rated tools, business process, etc. in the product database

at a particular time. Its main function is managing

and configuring different aspects of a single product

definition based on product structure management, and it

manages data that are correlative with product structure

and created in different work stages. Product configuration

management for net-based collaborative design can

make geographically dispersed enterprises share the same

product-configuration results in the whole product life-

cycle.

The main functions of this tool are as follows:

1. Configuration-result maintenance. This module in-

cludes viewing, adding, deleting, and modifying

function for configuration result.

2. Part/component replacement/interchange. Designers

can replace or interchange some part/components

with replaceable or interchangeable parts/compo-

nents in the configuration result.

3. Configuration variable maintenance, default condi-

tion maintenance, confine condition maintenance,

version validity maintenance, structure validity main-

tenance, and configuration condition maintenance.

All these functions mainly support the set of

Figure 8. Function structure of the constraint-based

conflict management tool. Figure 9. Conflict-management tool.

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configuration conditions and confine conditions,

which are the basis of product configuration.

4. Configuration rule maintenance. This supports the

management of configuration rules defined by the

user. We combined version configuration, variable

configuration, and validity configuration, and pro-

posed a combined configuration method. Geogra-

phically dispersed designers can choose one or more

configuration methods to build configuration rules

and then configure a special product according to

the priority rank set by the user.

5. Viewing properties of part/component. Geographi-

cally dispersed designers can acquire knowledge of

parts/components by viewing the properties of

special parts/components.

The interface of the collaborative product configuration

tool is shown in figure 10.

5.5. Visualization document management

There are many and varied documents in collaborative

design. In order to view and use all kinds of documents, we

developed a visualization document management tool

through Web technology. Geographically dispersed de-

signers can view or mark up the same document online,

enabling them to manage, develop, and use product

information resources effectively. It can also provide service

for collaborative product development.

The main functions of this tool are as follows:

1. Viewing document. Geographically dispersed de-

signers can view many kinds of documents online,

such as .txt, doc, pdf, jpg, bmp, dwg, wrl, and so on.

2. Maintaining document. This module includes docu-

ment checking in, document checking out, document

upgrading, document citing, document deleting, and

metadata modification.

3. Marking up document. We integrated a collabora-

tive viewing and markup tool here to support the

collaborative markup of special documents online.

4. Document retrieval. This includes single condition

retrieval and combined condition retrieval.

Figure 11 shows the interface of this tool.

5.6. Collaborative task management

Net-based collaborative product design is a characteristic

design approach. The assignment and management of the

design task play important roles in collaborative design.

According to separate design tasks, geographically dis-

persed designers design a product concurrently, interac-

tively, and collaboratively. A collaborative design process

can be well controlled by efficient management of the

design task.

At the beginning of collaborative design, the final target

of the project should be made certain, such as the function

target, performance target, quality target, etc. The whole

scheme of project implementation can be obtained accord-

ing to the final target. Then, the project can be broken

down into at least two sub-tasks because one collaborative

design task needs at least two cooperators. For complicated

projects, the design task can be carried out in stages. The

design task will be broken down according to the target of a

certain stage, and the design constraints and time

constraints among stages and sub-tasks can be defined.

The task breaking-down method of collaborative design is

shown in figure 12.

Based on these design ideas, we developed the colla-

borative task-management tool. The tool supports the

Figure 11. Visualization document-management tool.Figure 10. Collaborative product-configuration tool.

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lifecycle management of the project from the contract

signing to completion in a collaborative design environ-

ment. The whole collaborative design project would be

completed very well through organizing, controlling, and

monitoring the implement process of the project.

The tool’s main functions include the following:

1. Task planning. Designers can make a certain

sequential task set, concurrent task set, and coupling

task set according to the information requirement

relationship between design tasks and then deter-

mine the rational executive sequence of the design

task based on the information requirement.

2. Task maintenance. This supports the breaking down

and maintenance of the design task.

3. Task process monitoring. Designers can know the

executive process information of the task by

monitoring the task process.

4. Task statistic. Designers can count task occupation

time by this function.

5. Task retrieval. This supports single condition

retrieval and combined condition retrieval. De-

signers can retrieve task information, task resource

information, and so on.

Figure 13 is the interface of this tool.

5.7. Collaborative design-resource management

Design resource is the knowledge and experience accumu-

lated by designers over a long time. Establishing an

effective collaborative resource repository can make the

designing knowledge and experience from different levels

and different fields available to users or experts independent

of time and space. This helps to improve design quality,

reduce unnecessary repeated work and waste of resources,

and at the same time provide support for collaborative

product creativity.

In this paper, the parts resource, standard part resource,

material resource, document resource, design sample

resource, and design rule resource, which are widely used

in the collaborative design process, are generally considered

the collaborative design resource. Our research sets up a

corresponding resource repository to organize and manage

them. The standard parts repository, material repository,

and document repository are the traditional management

contents of PDM. When geographically dispersed designers

develop products according to the design request, they can

do so without the manual. Instead, they can query and

quote resources from the libraries conveniently and

quickly. The design part repository stores the product or

part information so collaborative designers can perform

quoting or transforming design to the existing products or

parts. The design sample repository stores the previous

successful samples. Collaborative designers can search the

design samples that most match the characteristic of design

targets and then perform appropriate modifications to

make them suit the present design target. The modified

successful design sample will be restored into the reposi-

tory. The design rule repository stores the if-then rule

related to certain fields.

The main functions of the collaborative design-resource-

repository management tool include the following:

1. Resource repository maintenance. This realizes the

effective organization and management of the

collaborative design resource and supports integrity

and consistency check of the collaborative design

resource. Because each kind of design resource has a

different information expression model, the system

provides saving, viewing, modifying, and deleting

functions for each design-resource repository.

2. Design-resource retrieval. Reuse of the collaborative

design resource cannot occur without an efficiently

Figure 12. Task tree model of collaborative design.

Figure 13. Collaborative task-management tool.

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and quickly retrieved function. This module pro-

vides simple searching, category searching, custo-

mized searching, similar searching, and elicitation

searching as well as other retrieve functions so that

designers can search for the design resource they

need conveniently and quickly.

3. Information-sharing interface. This module mainly

realizes the sharing and integration of design

resource of diverse locations, places, and hetero-

geneous structure in the network environment.

This system makes use of an XML document as the

mediate format of heterogeneous design resource, and the

shared design resource is finally stored in the relation

database; therefore, the XML document is only used to

perform data exchange.

The interface of the collaborative design resource

repository management tool is shown in figure 14.

6. Application examples

We have applied the CoDesign Space system as the support

environment and tool to the design and development of

some spaceflight products. The research and development

of spaceflight products is a complicated project, contrib-

uted to by technologists from many fields. The structure of

spaceflight is also complex. CoDesign Space collaborative

information management platform efficiently realized the

management of personnel and product structure. Figure 15

shows the interface of the product-development-group

personnel-management system.

Large quantities of differently formatted documents are

involved in the development of spaceflight; they come from

different design phases and are generated by different

designers. In the whole collaborative design process, it is

necessary to manage these documents properly and clearly

for efficient query and browsing. At the same time, because

there are numerous categories of documents formats, the

CoDesign Space visual-document management tool shows

its special advantage. Without installing any additional

software, the visual-document management tool supports

user searching, viewing, and annotating of multi-format

documents conveniently, and geographically dispersed

users can collaboratively view and annotate the document.

Figure 16 is a work interface by which many experts

collaboratively communicate. By using the collaborative

tool ‘3D model collaborative view and annotate tool’

provided by CoDesign Space, they can discuss where a

certain camera should be fixed on the spaceflight product.

A design expert can announce their opinion, while other

design experts in distributed places will see the same picture

Figure 14. Resource-management tool.

Figure 15. Set-up for a certain spaceflight product work-

group.

Figure 16. Collaborative discussion based on 3D models.

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on their own computers. They can also have real-time

exchanges and discussion.

With the collaborative design tool ‘3D-VRML model

collaborative virtual assembly system’ provided by CoDe-

sign Space, designers can perform collaborative virtual

assembly using the parts designed by different CAD

systems. The tool also supports interference detection,

assembly sequence layout, assembly path layout, etc., as

figure 17 shows.

We applied the CoDesign Space in a certain spaceflight

development and resolved problems in this sophisticated

spacecraft such as collaborative work of experts from

different areas, product-structure management, and multi-

format document collaborative viewing and markup. This

shortened the development time, thus providing a good

support environment for the development of complicated

spaceflight.

7. Conclusions

In this paper, the concept and related research on net-based

collaborative design are discussed, a multi-mode collabora-

tive design method is proposed, and several typical

collaborative design modes are defined. The problem of

product data sharing and integration is resolved by XML

and VRML technology. Based on this, a general type net-

based collaborative product design support system, CoDe-

sign Space, is designed and realized. The system developed

has an open and flexible structure and has the advantage of

being scalable and customizable. It can be configured to

form various application systems and can be integrated

with other systems.

Collaborative design is a complex systemic research

project; the implementation of this system is, however,

partial at this stage. Further research is needed on the

negotiation mechanism and on the process of collaborative

design, the workflow management in distributed network

environment, and the integration between XML and

VRML, the goal of which is to satisfy the different

requirements of collaborative design in different ways and

make the collaborative design more effective in a network

environment.

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