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This article was downloaded by: [University of Hong Kong Libraries]On: 09 October 2014, At: 19:07Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK
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
To link to this article: http://dx.doi.org/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.
268 L. Tian et al.
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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.
CoDesign Space 275
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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.
CoDesign Space 277
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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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