Current computer-based mechanisms for asynchronous communication include electronic mail and computer conferencing systems. Electronic mail supports one-to-many communication patterns and has serious drawbacks when used for group interaction. Computer conferencing systems are typically implemented to execute on a single processor and users at remote locations access the shared information by logging on from terminals connected by dial-up lines. This paper presents an architecture for a network-based system that models communication as group access to shared multimedia objects. It also describes the features of a computer conferencing system that was implemented for Bitnet, a network of academic computers, and Vnet, the IBM internal network.

DIRECT is a multiprocessor database machine designed and implemented at the University of Wisconsin. This paper describes our experiences with the implementation of DIRECT. We start with a brief overview of the original machine proposal and how it differs from what was actually implemented. We then describe the structure of the DIRECT software. This includes software on host computers that interfaces with the database machine; software on the back-end controller of DIRECT; and software executed by the query processors. In addition to describing the structure of the software we will attempt to motivate and justify its design and implementation. We also discuss a number of implementation issues (e.g., debugging of the code across several machines). We conclude the paper with a list of the "lessons" we have learned from this experience.