Groupware communicates by sending messages across the network, and groupware programmers use a variety of formats for these messages, such as XML, plain text, or serialized objects. Although these formats have many advantages, they are often so verbose that they overload the system's network resources. Groupware programmers could improve efficiency by using more compact formats, but this efficiency comes at the cost of increased complexity, reduced convenience, and reduced readability. In this paper we propose an alternate approach for improving efficiency -- an automatic compression system that transparently minimizes verbose formats. Our general message compressor -- GMC -- automatically finds and removes redundancy in message streams, without any knowledge of the contents or structure of the message, and without any need for the programmer to change the way they work. In tests with realistic message traces, GMC reduced text messages to 20% of their original size, XML messages to 8% of the original, and serialized objects to 9%. Although not as compact as a hand-coded representation, GMC provides most of the compression benefits with almost none of the work -- it allows groupware programmers to use convenient message formats without compromising transport efficiency.

Although telepointers are valuable for supporting real-time collaboration, they are rarely seen in commercial groupware applications that run on the Internet. One reason for their absence is that current telepointer implementations perform poorly on real-world networks with varying traffic, congestion, and loss. In this paper, we report on a new implementation of telepointers (HPT) that is designed to provide smooth, timely, and accurate telepointers in real-world groupware: on busy networks, on cable and dialup connections, and on wireless channels. HPT maintains performance at usable levels with a combination of techniques from multimedia and distributed systems research, including UDP transport, message compression, motion prediction, adaptive rate control, and adaptive forward error correction. Although these techniques have been seen before, they have never been combined and tailored to the specific requirements of telepointers. Tests of the new implementation show that HPT provides good performance in a number of network situations where other implementations do not work at all - we can provide usable telepointers even over a lossy 28K modem connection. HPT sets a new standard for telepointers, and allows designers to greatly improve the support that groupware provides for real-time interaction over distance.