Keywords: multi-agent, SOAP, web service, steel member, design, CAD, product model, distributed processing, distributed object, code checking, XML.

In structural detailed design, engineers determine the section dimensions of each member and check all the members for compliance with applicable design codes. If a member violating any code is found, engineers have to re-design the member and perform code checking repeatedly until all members satisfy the codes. In addition, if the design change is significant, they have to analyse the total structural system again. The whole process is time-consuming and error-prone.

A number of research efforts have been made in order to develop efficient design environments by using 3D CAD systems and product models. These design environments can provide capability of fairly smooth data transfer among 3D CAD systems and non-CAD application systems by the interoperability. Although they improve the efficiency of the design process, engineers have to spend time and consciousness for data transfer among systems yet. This problem may be solved by putting all related systems together and by making a single package. But this solution would lose a number of other advantages such as free competition among software developers and vendors.

In order to solve this problem, we believe that intelligent agents, which can support engineers and designers autonomously in various ways, operating in the background and without users' consciousness. Thus, we previously developed multiple agents and developed Multi-Agent CAD [1] by integrating them with a 3D CAD system while using an IFC-based product model for sustaining the interoperability. In this system, one agent autonomously checks the compliance of the user's design with a design code when the engineer designs steel members in a 3D CAD system. The other agent checks external constraints such as constructability and economy, and gives the user comments and advices while the engineer is designing. Although the developed Multi-Agent CAD works well, it takes much effort and time for each user of the system to maintain the agents and CAD system for upgrades of the system and other software packages because the system is installed in each computer.

In this paper, therefore, a new framework for the Multi-Agent CAD environment is presented. In the new framework, instead of installing all agents in each computer, the main content of each agent resides in its developer's computer and the Multi-Agent CAD system in a user's computer has the agent interface, which is working autonomously in the background and which sends a message, when necessary, to the agent residing in the remote computer via Internet. Thus, agents are distributed in the Internet and when the agent receives a message from a remote Multi-Agent CAD system, the agent performs its task and sends its result or answer to the user's computer. This has been accomplished by incorporating the Simple Object Access Protocol (SOAP) and Web Service technologies into the Multi-Agent CAD system.

In this research, we developed a prototype steel member design system on the basis of the proposed framework. This system has three agents: (1) a simple code checking agent, (2) a design situation judging agent, and (3) a database agent. The code checking agent checks the section that the user has selected against the given loads in the background and gives the user the result when the design violates the design code. The design situation judging agent checks various design situations such as whether the beam heights of adjacent beams are the same and whether centres of up and down columns are the same, etc. The database agent retrieves section data of steel members from the database developed by American Institute of Steel Construction (AISC). These agents have the agent interface in the Multi- Agent CAD system in the user's computer and the corresponding Web Service in the developer's computer.

We applied this system to a design of a steel frame, and found that most users felt that some knowledgeable and experienced engineer was inside the computer and gave them alerts and advices when necessary. Thus, we believe our prototype system showed the feasibility, effectiveness, and practicality of the proposed framework. One main advantage of using SOAP for multi-agents is that users do not have to worry about agent upgrading, which take place often in terms of design codes. The other advantage is software developers do not have to worry about firewalls when agents send and receive messages over the Internet. We are developing other agents to enhance the system as future work.

1

N. Yabuki, J. Kotani, et al., "A 3D-CAD Environment with a Multi-Agent System and a Product Model", Journal of Civil Engineering Information Processing Systems, 11, 1-8, 2002 (in Japanese).

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