It has long been the objective of interface design to remove the physical interface as a barrier between a user and the work she wishes to accomplish via the computer. While many of the advances in usability have come from the development of techniques that allow a designer to build a system based on modelling of the user's tasks and mental models, we are still largely stuck with the same input devices (keyboard, mouse and tiny display monitor) that have been commercial standards for 15 years. This physical interface is anything but transparent to the user and it violates ubicomp vision of pervasive computation without intrusion. As the vision of ubicomp is fulfilled and computational services are spread throughout an environment, advances are needed to provide alternative interaction techniques.
For example, in Classroom 2000, it is important that the electronic whiteboard look and feel like a whiteboard and not a computer. In a traditional classroom, the lecturer comes to class and only has to pick up a marker or chalk to initiate writing on the board. Interaction with the electronic whiteboard needs to be that simple. Our initial Zen* system required a lecturer to launch a browser, point to the ZenPad Web page, select the class, give a lecture title, set up the audio and video encoding machines and authenticate themselves to the system before class could begin. As class begun, three people were needed to ``start'' the system, synchronizing the beginning of three different streams of information. Hardly a transparent process! In fact, had we not provided human assistance to set up the class, we would not have had so many adopters early on. What we lacked in an automated transparent entry to the system we had to make up in human support. Today, the situation is still not ideal, but the start up procedure is limited to starting a single program, entering the title for the lecture and pressing a button to begin lecture. The goal is to make the system vanish even further, ultimately returning to the situation in which the lecturer simply enters the room, picks up the pen and begins to lecture.
As another example, the Cyberguide prototypes varied quite a bit in the interface provided to the end user. The goal was to reproduce the flexibility of a human tour guide, which meant allowing for questions at arbitrary times with constant knowledge of where the traveller was located. This knowledge can be used to provide an apparently flexible and ``intelligent'' interface. Limited speech interaction is augmented by knowing what a person is attending to and preparing the system to recognize utterances with related keywords. In addition to providing end-user flexibility, there is a development challenge to provide similar functionality across varied interfaces and interaction techniques.
Transparent interaction techniques is a very active area of research which includes handwriting and gesture recognition, freeform pen interaction, speech, computational perception, tangible user interfaces (using physical objects to manipulate electronic information) and manipulation interfaces (embedding sensors on computational devices to allow for additional modes of interaction).