A framework for developing a unified B2B e-trading construction marketplace

A framework for developing a unified B2B e-trading

construction marketplace

Heng Lia,*, Jiannong Caob, Daniel Castro-Lacouturec, MiroslAaw Skibniewskid

aDepartment of Building and Real Estate, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, ChinabDepartment of Computing, The Hong Kong Polytechnic University, Hong Kong, ChinacSchool of Civil Engineering, Purdue University, West Lafayette, IN 47907-1294, USA

dDivision of Construction Engineering and Management, School of Civil Engineering, Purdue University, West Lafayette, IN 47907-1294, USA

Abstract

With its great explosion and the advancement of related technology and services, such as the World Wide Web (WWW), the

Internet has provided a rich environment for developing Internet-based electronic commerce (e-commerce) applications in

construction. Among the different types of e-commerce, business-to-business (B2B) is the most widely used. The B2B e-trading

marketplaces (also called B2B-exchanges), which have sparked a revolution in the way of trading products between buyers and

suppliers, are an essential component of B2B applications. However, many e-trading marketplaces have been developed and

hosted by different construction products and services providers, and each forms a closed system with their own customers and

clients. In this paper, the concept of e-union is presented, which integrates the services provided by different e-trading

construction sites to provide an open e-trading service. The design of a mobile agent-enabled framework for building such an

open e-trading marketplace environment is described, along with a prototypical implementation.

D 2002 Published by Elsevier Science B.V.

Keywords: Framework; B2B; E-trading; Marketplace

1. Introduction

Over the last few years, the Internet has evolved

from being a scientific network only, to a platform that

is enabling a new generation of business. More and

more companies and organizations are doing different

types of business and offer value-added services on the

Internet [1]. While the first stage was fueled by the

vision and innovation of business-to-consumer (B2C)

Internet companies, the current phase is defined by

the leadership and market success of companies en-

gaged in business-to-business (B2B) electronic com-

merce (e-commerce) [2].

The B2B e-trading marketplaces, which allow

large communities of buyers and suppliers to meet

and trade with each other, are an essential component

of B2B e-commerce applications. They resemble

stock exchanges in many ways, including the way

they are set up and organized and the trading methods

they employ—but they are trading physical commod-

ities such as doors, tiles and steel. They enable a

many-to-many relationship between multiple buyers

and sellers in the construction industry, who come

together and find each other in the cyberspace. They

allow participants to access various mechanisms to

buy and sell almost anything, from services to direct

0926-5805/02/$ - see front matter D 2002 Published by Elsevier Science B.V.

PII: S0926 -5805 (02 )00076 -6

* Corresponding author. Tel.: +852-2766-5111; fax: +852-276-

42572.

E-mail address: [email protected] (H. Li).

www.elsevier.com/locate/autcon

Automation in Construction 12 (2002) 201–211

materials. Buyers and suppliers leverage economies

of scale in their trading relationships and access a

more ‘‘liquid’’ marketplace. Sellers find buyers for

their goods, buyers find suppliers with goods to sell.

Many-to-many liquidity allows the use of dynamic

pricing models, thus further improving the economic

efficiency of the market.

Construction companies are now conducting their

business using Web-based e-commerce system. Many

believe that e-commerce can provide a win-win sit-

uation for both suppliers and buyers, as e-commerce

can provide an expanded marketplace within which

buyers and suppliers can communicate directly with

each other. E-commerce might bring the answer

awaited for clients or construction firms, that is, to

create the solution for the procurement of materials

using non-traditional methods, avoiding delays, high

prices, lack of specified products, etc. [3]. Online

construction trading markets are not limited by the

physical limitations of store spaces and can carry a

much larger variety of products and different styles and

sizes. At the same time, buyers can search through a

wide range of products with low transaction costs at

any time convenient to them. More importantly, the

direct communication between buyers and suppliers

will cut off the multiple layers of middlemen between

suppliers and buyers. These middlemen take commis-

sions and fees from both buyers and suppliers. The use

of e-commerce will therefore directly benefit the

buyers so they can efficiently purchase cheaper prod-

ucts with a variety of choices [4].

The last several years have witnessed the emergence

of online B2B e-trading marketplaces. Well-known

examples include Catex, Chemdex, e-STEEL, Metal-

Site, and VHCome [5]. Currently, however, it is often

the case that, within a particular industry such as the

construction industry, many e-trading marketplaces

have been developed, owned and/or hosted by different

companies. Each of the e-trading marketplaces forms a

closed system with their own customers and clients.

The totality of these e-trading marketplaces appears to

be islands in the sea, as they are isolated and with no

interoperation between each other. In this paper, a

framework is presented for developing an interoperable

e-trading marketplace for the construction industry by

linking all the existing e-trading marketplaces, as any

single e-trading marketplace may not be able to meet all

the requirements of the buyers. The ability of market-

places to interoperate extends the idea of liquidity and

network effect by joining more buyers with more

suppliers but does not sacrifice the ability of each

marketplace to be highly specific to the supply-chain

node or target buyer group it serves. The concept of

‘‘e-union’’ is described, which integrates the services

provided by different e-trading marketplaces in the

construction industry to provide an open and unified

e-trading marketplace, or e-union, which is enabled by

the use of a mobile agent.

2. The e-union concept

The unique feature of a B2B e-trading marketplace

is that it brings multiple buyers and sellers together (in a

‘‘virtual’’ sense) in one central market space and en-

ables them to buy and sell from each other at a dynamic

price which is determined in accordance with the rules

of the exchange. On the Internet, every web site, which

enables buyers and sellers to come together and find

each other, is really a ‘‘virtual’’ e-trading marketplace.

An e-trading marketplace was developed as part of

VHBuild, a Web-based mediation service for construc-

tion project management in Hong Kong [6]. Fig. 1

shows selected screen dumps of the system’s web

interface. The service is provided to mediate among

the different parties involved in a construction project

for various project management activities, including

project initiation, tendering, materials purchasing,

project monitoring, project information querying,

decision making, etc. These activities are systemati-

cally organized and coordinated around a construction

project, with a close modeling of the data flow and

workflow in the building and construction industry.

The system also provides an e-trading marketplace for

advertising, marketing and buying/selling of construc-

tion materials and equipment.

The Web-based e-trading marketplace contains two

major functions: providing trading information and

facilitating trading transactions. Users will log onto

the system as either buyers or sellers of construction

materials. The sellers can upload their product infor-

mation and find out summary information about their

customers and their transactions. The buyers can search

certain types of products, giving their requirements

such as brand, model, quality, price, etc., or they can

browse the products on display. When the products

H. Li et al. / Automation in Construction 12 (2002) 201–211202

requested by a buyer are found, the information will be

displayed to the buyer and the contact information of an

agent closest to the buyer’s location will also be sent to

the buyer. The buyer can negotiate with the agent about

the price, or send an order to the agent by filling some

forms online. If the user could not find the products he/

she wants, the system will keep their inquiry in a place,

which can be visited by the sellers.

In recent years, several other construction e-trading

sites have appeared on the Web. They are operated by

different organizations and attracted different group of

clients. They specialize in trading materials from

suppliers in different regions. From time to time,

however, clients of one e-trading system would like

to buy some materials that are not available in that

system but offered in other sites. One way to solve

this problem is to let the client register at several

e-trading marketplaces and search these sites one by

one. Fig. 2 illustrates this approach.

To provide better value-added services to the

clients, we present the concept of an e-trading union

by linking together relevant e-trading marketplaces so

that cooperation between the e-trading marketplaces

can be facilitated. In the e-trading union, when an

e-trading site does not have the material requested by

one of its registered clients, the site will send a request

Fig. 1. VHBuild, a web-based mediation service for construction project management.

Fig. 2. Traditional approach to searching and buying a product.

H. Li et al. / Automation in Construction 12 (2002) 201–211 203

to other e-trading sites in the union. The remote

e-trading site will treat the request as one from an

associated client. An associate client cannot directly

make use of the service of the e-trading marketplace

as its registered client. When the material requested is

found, the remote site will inform the requesting

e-trading site, which will decide whether to put an

order on behalf of its client. Once a deal is made

between the two e-trading sites, the requesting site

will inform the remote site the contact information of

an agent to whom the material should be delivered; it

will also display the material information to the buyer,

together with the contact information of an agent

closest to the buyer’s location. The remote e-trading

site will charge some extra amount of money, usually

a certain percentage of the normal price, for providing

the service. Fig. 3 illustrates this open marketplace

approach.

3. A mobile agent-enabled framework for e-union

Since individual e-trading systems are developed

based on different computational architectures, plat-

forms and software, it is not a trivial task to make them

interoperable. There are several issues that need to be

addressed for realizing the e-union concept. The first

issue is how an individual e-trading system finds the

service from other sites and communicates with each

other. The second issue is how one system understands

the various kinds of data from other systems, such as

the query, order and product information. Particularly,

the date may be in different formats and databases for

the representation and storage. In order to solve these

problems, we developed a mobile agent-based frame-

work for implementing the e-union.

A mobile agent is a computer program that can

autonomouslymigrate between network sites, i.e. it can

execute at a host for a while, halts execution, dispatches

itself (together with its data and execution state) to

another host and resumes execution there—all under its

own control [7,8]. It has been found that mobile agent is

especially suitable for structuring and coordinating

distributed applications running in a wide-area envi-

ronment like the Internet [9–11]. Such an environment

is characterized by a larger number of heterogeneous

nodes with dynamically changing services and resour-

ces, high variation of connectivity both in performance

and in reliability, high variation of workload and net-

work traffic, mobility of hosts, etc. Mobile agents can

move through the network of sites to search for, filter

and process information they need to accomplish their

tasks [12–14]. Sending mobile agents to the remote

server results in a large performance improvement,

because they can reduce the number of times one site

contacts another and they can filter out non-useful

information and thus reduce the consumption of com-

munication bandwidth. Furthermore, mobile agent

Fig. 3. Open e-trading union.


brings flexibility and scalability into distributed,

dynamic systems due to its ability to encapsulate

policies, convention and algorithms and its ability to

be dynamically created and destroyed.

In our framework, an e-trading site joints the union

by broadcasting its address and service interface to

other members in the union. The membership infor-

mation is kept at each e-trading site in a database. Mo-

bile agents are dispatched to other member sites for

querying and ordering construction materials that are

not available at the local site. Fig. 4 shows the ar-

chitecture of the mobile agent-enabled e-union system.

The workflow of the e-union can be described as

follows. The client first issues a query for information

about a certain construction material. The local e-tra-

ding site searches its material database and finds out

that the requested material is not available. It will then

forward the client query to the Query Generator. The

Query Generator looks up the e-union database for

information about members in the union. It then gene-

rates remote queries by formatting tuples of e-trading

site address and query statements, and passes these

queries, together with search criteria, to the Static

Agent, which is the master agent. The Static Agent is

responsible of creating mobile agents to carry out the

remote queries. The created mobile agents will be

dispatched to remote e-trading sites. Upon arrival, a

mobile agent interacts with the remote e-trading site to

connect to the materials database server, executes the

query statements, analyzes and filters the retrieved

records, extracts useful data as result and travels back

to the original e-trading site. After all mobile agents

return, the Static Agent at the original site will gather

the partial results and return the final result to the

client.

There are two types of mobile agents: Porter agents

and Traveler agents. A Porter agent is dispatched to a

particular remote e-trading site, executes the given

Fig. 4. Mobile agent-enabled e-union architecture.


query, retrieves result and then sends back the result to

the Static Agent at the original site. A traveler agent,

on the other hand, can travel with an itinerary over the

Internet, from one e-trading site to another. At each

visited site, it functions in the similar way as the

Porter agent. However, it can store the partial results

obtained at each site and carry them with it until it

finds the expected information or travels through all

the member sites in the e-union.

To facilitate the interoperability between the mate-

rial databases at each e-trading sites, we have devel-

oped a solution using XML. Databases and XML offer

complementary functionality for storing material data.

Databases store data for efficient retrieval, whereas

XML offers an easy information exchange that enables

interoperability between different material databases.

In our solution, database tables are converted into XML

documents. These XML documents can then be used as

a data-exchange format, presented as HTML pages,

and searched with XML-based query languages. In this

way, the material records from different databases can

be combined in their XML document format and

analyzed and filtered by the mobile agents.

Another possibility for triggering actions on e-trad-

ing sites and conveying information to the registered

clients is by modeling XML applications through

unified modeling language, or UML. UML defines a

standard language and graphical notation for creating

models of business and decision-based systems [15].

The supply chain of construction materials is a suitable

environment for this endeavor, since there are per-

manent interactions among customer, supplier, other

e-sites and delivery agents. With the use of UML

diagrams featuring the workflow of information, it is

possible to generate the interactions and decision

processes necessary to reflect the abovementioned in-

teractions. Fig. 5 displays the workflow and interaction

diagram of typical construction materials e-business

applications.

The Internet serves as the environment where the

e-business system will provide an efficient coordina-

tion and communication of tasks and resources in the

procurement of construction materials. By facilitating

communication as a basis for information exchange

and conflict resolution, the proposed e-business model

Fig. 5. Interaction diagram of an e-business/e-trading solution for

construction materials management using UML.

Fig. 6. An e-business solution for the procurement of steel reinforcement using XML [16].


is capable of providing the overall process of estima-

tion, revision and procurement of steel reinforcement

with tools for integration and cooperation along the

supply chain. The tools that constitute the architecture

of the collaborative e-business system, i.e. HTML

(Hyper Text Markup Language), ASP (Active Server

Pages) and XML, will allow substantial communica-

tion among participants through the Internet [16].

A proposed model of e-business interaction in

construction materials management using XML offers

a dynamic approach to the flow of information along

the model network, as seen in Fig. 6.

The bcXML was adopted as the data infrastructure

[17]. The bcXML stands for Building-Construction

XML developed by Information Societies Technol-

ogy, aimed at helping the European building and

construction industry to develop, demonstrate and

disseminate a new communication technology tailored

to the needs of construction industry. The bcXML is

the core component of the project eConstruct, which

addresses the problems of insufficient information

structuring of data exchange. The bcXML is seman-

tically rich and supports many of the notions used in

practice. In particular, the semantics included in

bcXML support the e-commerce communication

about construction products.

Fig. 7 describes the XML-enhanced architecture in

which a layer is placed between mobile agent and

Fig. 7. XML-enhanced e-union architecture.

Fig. 8. Major components of the prototype.


material database. Instead of querying the database

directly, the mobile agent submits the query to the

XMLTool and gets back the result in XML document

format with the bcXML Schema. The XML Tool

receives the query request from the mobile agent,

requests the Parser to retrieve the records in XML

document. Because of the material database’s highly

regular data storage structure, the material data can be

first mapped into data-centric XML documents. The

Parser extracts the desired data from the database by

executing the query statements. The data in table

format is then transformed into an XML document

with the bcXML Schema.

In order for the Parser to generate XML documents

validated with bcXML Schema, the material database

should be constructed following the specification of

the bcXML. The material name, data type, data unit

should be stored by using bcDictionary [17] and the

database schema should match the bcXML Schema.

4. Prototypical implementation and experiments

To demonstrate the effectiveness of the proposed

framework, we have implemented a prototype of the

e-union using the IBM Aglet mobile agent platform

[18]. The Aglet is a Java-based mobile agent frame-

work. The IBM Aglet platform also provides an aglet

viewer called Tahiti and aglet servers, which are

powerful machines that can host large number of

aglets, Mobile agents in our framework are imple-

mented as aglets and use the ATP protocol for

interactions. Using ATP, the Aglet Tahit Server

installed at each e-trading site allows the mobile

agents to navigate and perform query on the materials

data. Oracle 8 is used as the materials database server.

In this prototypical implementation, we did not imple-

ment the XML-enhanced architecture.

Fig. 8 shows the major components of the proto-

type. The Query Generator is implemented with a Java

servlet program, which accepts client’s request via the

user interface (see Fig. 9) and generates SQL state-

ments used for querying materials databases of remote

Fig. 9. Screen dump of user interface for query.

Fig. 10. Search results by Porter agents.


e-trading sites. It is also responsible of generating the

itinerary for mobile agents to be dispatched.

Both Porter agents and Traveler agents have been

implemented. Porter agents are dispatched when paral-

lel search is used. If a Porter agent arrives successfully

at the destination e-trading site, it extracts the SQL

statements attached in the message carried by it. Before

executing the SQL statements, the Porter agent first

gets the information from the Aglet Server at the visited

site on connecting to the materials database at the site.

The information includes the connection string, user-

name/password for connecting the database and the

database driver. The Porter agent then establishes a

connection to the database. After the connection is

established, the Porter agent gets the data from the

database. Before returning the results back to the

applet, the Porter constructs the data into HTML table

format. Fig. 10 shows the results returned by three

Porter agents. The master agent at the original e-trading

site needs to assemble the results from all the Porter

agents into the final result and sends to the client.

On the other hand, a Traveler agent can be dis-

patched to travel through all the specified remote sites.

The method for connecting to the materials database at

a visited e-trading site is similar to that used by a Porter

agent. After retrieving the material data from the

database, the Traveler agent stores the results into its

‘‘Pocket’’ which are carried by the agent throughout

the whole itinerary. In each site, when the desired

material records are found, they will be compared with

the records which were found in the previous sites in

order to filter out redundant or useless information.

New and useful records are added to the Pocket. After

Fig. 11. Search results returned by Traveler agent.

Fig. 12. Total time for searching within five e-trading sites.


the whole trip completes, the Traveler agent returns the

results to the master agent at the original e-trading site.

The Traveler agent can also be instructed to return

either the first-fit result or the best result (see Fig. 11).

Experiments have been performed to evaluate the

performance of the mobile agent-enabled framework.

Five SUN workstations are set up with Aglet Tahiti

servers and iPlanet Web servers supporting Java

Servlets. For comparison, we have also implemented

a message-passing version using Java servlets com-

munications. In this version, the Query Generator at

the local e-trading site queries to the e-trading Union

Information database and forms a sequence of pairs of

address and query statement, one for each e-trading

site to search. It then submits the information to the

local Query Submit Servlet, which submits the query

to the remote e-trading sites one by one. The Query

Execute Servlet at a remote site receives the query,

executes it and then returns the result.

Fig. 12 shows the average total time for the three

different approaches. It can be seen that the Porter

agent approach performs the best. This is because of

the parallelism in their executions. However, this

approach will result in many mobile agents being

dispatched in the network, increasing network traffic.

In addition, as we can observe from Fig. 13, in terms

of the time spent on each individual remote site,

Porters perform worse than the other two approaches.

From Fig. 13, we can see that the Traveler

approach is faster than the Servlets approach. How-

ever, it may not reflect the real situation. In our

experiments, both Tahiti server and iPlanet server

were shut down and restarted before collecting the

next set of statistics data. This is to prevent the effect

of caching of the previous result in memory on the

performance, especially in the servlet/web server.

When the servers were not shut down, we observed

that the time required by the two approaches became

closer. On some occasions, the performance of the

servlet approach was even better.

Fig. 13. Total time for searching at a single e-trading site.

Fig. 14. Network traffic generated by the Traveler and Servlet approaches.


Fig. 14 compares the performance of the Travelers

approach with the Servlets approach in terms of the

volume of data records transferred on the network. It

shows that the Traveler approach significantly reduce

network traffic.

5. Conclusion and future work

B2B e-trading marketplaces for the construction

industry present ideal structures for commercial

exchange, achieving new levels of market efficiency

by tightening and automating the relationship between

suppliers and buyers. Based on their ability to bring

buyers and sellers together online and thereby to create

dynamic pricing, B2B e-trading marketplaces are the

killer application in the B2B Internet revolution. In this

paper, we have presented the concept of e-union, which

integrates the services of separate e-trading market-

places to provide open, value-added e-trading services.

We have described a mobile agent-enabled framework

for building the e-union. A prototypical implementa-

tion was also presented which demonstrates the feasi-

bility of the proposed e-union concept. Experiment

results of performance evaluation have been reported.

Our future work includes implementing the XML-

enhanced architecture to achieve true interoperability

of the e-trading sites. Further experiments to evaluate

the various design tradeoffs and performance are

planned. Finally, we will investigate alternative ap-

proaches to building e-union, such as using Common

Object Request Broker Architecture (CORBA) or

integrating mobile agents with CORBA.

References

[1] D.L. Hoffman, T.P. Novak, P. Chatterjee, Commercial scenar-

ios for the Web: opportunities and challenges, Journal of Com-

puter-Mediated Communication 3 (3) (1995).

[2] B. Sculley, W. William, B2B exchanges: the killer application

in the business-to-business internet revolution, Proc. 31st Ha-

waii Int’l Conf. On System Sciences (HICSS31), Kona, Ha-

waii, Jan. 2000, University of Hawaii, Hawaii, pp. 149–154.

[3] D. Castro-Lacouture, D. Harmelink, M. Skibniewski, Appli-

cability of CAD software enabled with artificial intelligence for

drawing management and rebar take-off practices in the US.

Unpublished report prepared for VHSoft Software, Hong

Kong, Division of Construction Engineering andManagement,

School of Civil Engineering, Purdue University, May 2001.

[4] J.Y. Bakos, A strategic analysis of electronic marketplaces,

MIS Quarterly 15 (3) (1991) 295–310.

[5] S. Kong, H. Li, P.E.D. Love, An e-commerce system for

construction material procurement, Construction Innovation

1 (1) (2001) 43–54.

[6] H. Li, T.C. Wong, Intelligent web-based project management

system for large scale construction projects. Beijing, Proceed-

ings of Construction Management of Large-Scale Projects,

13–16 December 2000, Construction Engineering Press, Bei-

jing, pp. 149–152.

[7] D. Chess, C. Harrison, A. Kershenbaum, Mobile agents: are

they a good idea? IBM Research Report, RC 19887 (#88465)

3/16/95, 1995.

[8] D.B. Lange, M. Oshima, Seven good reasons for mobile

agents, Communication of the ACM 42 (3) (1999) 88–89.

[9] J. Cao, G. Chan, W. Jia, T. Dillion, Checkpointing and rollback

of wide-area distributed applications using mobile agents, Proc.

IPDPS 2001, University of San Francisco, San Francisco, USA,

April, 2001, pp. 22–34.

[10] S. Funfrocken, Integrating Java-based mobile agents into web

servers under security concerns, Proc. 31st Hawaii Int’l Conf.

On System Sciences (HICSS31), Kona, Hawaii, Jan. 1998,

University of Hawaii, Hawaii, pp. 34–43.

[11] R.S. Gray, Mobile agents: motivations and state-of-the-art sys-

tems, Tech. Report, Dept. of Computer Science, Dartmouth

College, April 2000. http://agent.cs.dartmouth.edu/.

[12] P. Dasgupta, N. Narasimhan, L.E. Moser, P.M. Melliar-Smith,

MAgNET: mobile agents for networked electronic trading,

IEEE Transactions on Knowledge and Data Engineering 11

(4) (July–August 1999) 509–525.

[13] S. Papastavrou, G. Samaras, E. Pitoura, Mobile agents for

world wide web distributed database access, IEEE Transac-

tions on Knowledge and Data Engineering 12 (5) (Septem-

ber–October 2000) 802–820.

[14] T. Sandholm, Q. Huai, Nomad: mobile agent system for an

internet-based auction house, IEEE Internet Computing 5 (2)

(2000) 80–86.

[15] D. Carlson, Modeling XML Applications with UML, Addison

Wesley, New York, 2001.

[16] D. Castro-Lacouture, M. Skibniewski, Development of an

e-business solution for the integration of steel reinforce-

ment supply chain in construction projects, Proceedings

for the First International Conference on Construction the

21st Century (CITC2002), Challenges and Opportunities in

Management and Technology. 25–26 April, 2002, Florida

International University, Miami, 2002, pp. 197–204.

[17] M. Bohms, G. te Brake, P. Bonsma, F. Tolman, R. van Rees,

Draft version of the bcXML Specification (D103draft),

D103-bcXMLdraft, IST-1999-10303 eConstruct, http://www.

eConstruct.com, 1999.

[18] D.B. Lange, M. Oshima, Programming and Deploying Java

MobileAgents,WithAglets, AddisonWesley, NewYork, 1998.


http:\\agent.cs.dartmouth.edu\

http:\\www.eConstruct.com

Documents

A framework for developing a unified B2B e-trading construction marketplace