An Internet-based Distributed Service Architecture

This paper describes a distributed architecture that enables the delivery of design services over the Internet. The architecture of an individual service is three-tiered. The first tier is a common communication protocol interface. The middle tier is the common product model interface. The third tier is the core of the design service. Though fundamentally decoupled, methods in the communication layer and the product model layer have been formalized to enable the aggregation of services and the support of problem decomposition. In addition, with the standardization of the first two tiers, it is possible to rapidly deploy various design services, both new and legacy applications, that can be easily made accessible via the Internet. As examples of design services, the prototype implements a project manager service with a companion CAD package, services that incorporate two legacy applications (a building code analysis service and a service that generates and displays an accessible path for a given floor plan design using motion planning and animation techniques), and a disabled access service that takes advantage of the decomposable infrastructure. INTRODUCTION Traditional CAD systems are monolithic in that all functions or “services” are bundled in a software package. With the maturation of information and communication technologies, the concept that distributed CAD services are delivered over the Internet, Internet-based Computer-Aided Design (I-CAD), is becoming a reality. Technologies are now readily available to make the network-enabled CAD environment possible. Specifically, the technologies include a standard product model and a distributed object environment that allows for the development and transfer of a design based on the standard product model. In order to fully-leverage the power of the Internet, engineering and design services should be able to interact in a formal yet flexible manner. Services should be able to combine existing services to provide added functionality. This paper describes the developed service infrastructure and the prototype implemented to illustrate a framework that provides design services over the Internet. The framework provides a means to distribute design services in a modular and systematic way. The protocol between services that has been developed specifies the manner in which services can aggregate, and this aggregation supports problem decomposition. In addition, users have the ability to select appropriate design services as opposed to having to use a large monolithic design tool. Furthermore, users can easily replace a service if a superior service becomes available without having to recompile the existing services being used. The framework provides a means to seamlessly integrate a legacy application as one of the modular design services in the infrastructure. With the standardization of the communication protocol and the exchange of product model data, integration of legacy applications as well as deployment of new design packages becomes a straightforward task. In the prototype implementation, a project manager service with a companion CAD package, two design applications with companion viewers that incorporate legacy applications, and a design application specifically tailored to take advantage of the decompositional features of the infrastructure have been developed. The project manager service acts as a design model repository as well as a portal to direct a client application to other services provided in the infrastructure. A companion CAD package, a client service of the project manager service, has access to the design repository of the project manager service and queries the project manager service for the location of other appropriate services available over the Internet. The first two applications are examples of services that incorporate legacy applications. The first design application is the integration of a service that performs compliance checking of a design against governmental regulations, in this case for disabled accessibility (ADAAG 1997). The second design 1 Copyright © 1999 by ASME