Pii: S0950-5849(99)00098-1

The development of groupware is a complex endeavor due to several inherent features not present in single-user applications. To address this complexity many authors have presented useful platforms that permit the reutilization of code to facilitate the implementation of groupware applications. However, design reusability could be of greater value than code reusability and facilitate the use and extension of groupware features. This paper describes COCHI (Collaborative Objects for Communication and Human Interaction), an extensible pattern system for groupware applications that aims to provide reusability and extensibility of design patterns represented as COCHI subsystems and implemented as a class framework. This pattern system has proved to be useful for the rapid development of groupware applications, while being flexible enough to incorporate important extensions to the original framework. Overall, it provides a good balance between ease of use and flexibility. q 2000 Elsevier Science B.V. All rights reserved.