Related Web Works

ECHT94 Workshop

By: Andreas Dieberger Vienna University of Technology Email: dieberger.chi@xerox.com

Keith Andrews Graz University of Technology Email: kandrews@iicm.tu-graz.ac.at ---------------------------------------------------------------------------- The workshop "Spatial User Interface Metaphors in Hypermedia Systems" was held on September 18, 1994 in Edinburgh in conjunction with ECHT94. Participants were selected on the basis of position papers, which were then distributed before the workshop. To promote discussion in advance of the workshop an e-mail discussion list was set up. In all, there were 11 participants at the workshop.

Spatial user interface metaphors essentially try to utilise human abilities to use space to organise objects and to navigate within structures like houses or cities. The use of space in a particular application depends on the goal of that application-be it to make structure explicit, to support navigation, or to support organisation. Well-known examples of spatial user interfaces metapors are the desktop metaphor, the Xerox Information Visualizer, and most virtual reality systems.

The position papers and the first round of discussion brought forth that the main interests of many participants were in easing information access and navigation using spatial user interface metaphors.

As a starting point for the workshop, Keith Andrews from Graz University of Technology gave a presentation of the Harmony client for Hyper-G. Harmony supports both hyperlinking within and between three-dimensional scenes and navigation through a dynamically generated information landscape.

Several topics were isolated as being relevant to the field of spatialuser interface metaphors. Due to time constraints not all of these issues could be discussed during the workshop.

Layout How should spatial structures be laid out? Should hand-crafted or automatically generated layouts be used? This issue is related to the goal of a system. Systems where users modify the spatial layout sometimes use spatial relationships to communicate with the machine or other users. An example of such a system, VIKI, was presented in an ECHT94 paper session. Automatically crafted spatial layouts can be used to show structure inherent to the information in the system.

Large Dynamic Multi-User Environments How should large, dynamic, multi-user environments be supported? An advantage of spatial metaphors is the ease with which people are able to communicate about spatial relationships, allowing collaborative navigation in such systems. Communication about the environment and navigation relies partly on static features (points of orientation) in the system: therefore systems should not be too dynamic.

What to Represent Spatially? Spatial layout expresses a (spatial) relationship: what is the meaning of this relationship? Hyperlink relationships map to a topological space, composite structures to a graph/set, and search results (from information retrieval) to a vector space. The content or attributes of nodes may be used to embellish the space, or the contents may themselves display some spatially meaningful structure.

Evaluation Evaluating spatial metaphors. Although many spatial metaphors have been proposed or even implemented, it seems that few systems have been evaluated on the usability of their spatial metaphor - at least in the field of hypermedia. This lack of evaluation makes the field of spatial user interface metaphors seem very immature.

Conventions In order to promote the transfer of knowledge between systems, "conventions" on the meaning of spatial layouts seem necessary. Conventions also should clarify the meaning of spatial icons or widgets (user interface elements). Spatial user interfaces and their elements should also show clear affordances (that is: they should visually communicate their use). Local neighbourhoods might have their own conventions, metrics, and customs.

"Magic Features" User interface metaphors are typically not an identical mapping from a source domain to a target domain (for instance, objects not falling off a virtual desktop). Features which extend the metaphor beyond the source domain (sometimes called "magic features") often make a metaphor particularly useful. In the context of spatial metaphors such magic features are especially interesting in navigation. The use and realisation of such features-especially for supporting navigation-has so far not been very well addressed in the literature.

Applicability of Spatial Metaphors Perhaps the most important issue concerning spatial metaphors is to decide when to use them and when not to. As user interfaces today tend to be very realistic, a spatial conception often seems appropriate. However spatial user interfaces are not a universal solution to navigation problems.

The results of the discussions clearly point to the need for detailed evaluation of spatial user interface metaphors. They might be useful in a smaller range of applications than is believed today. Like in all other user interface issues, these evaluations will probably show that there is no universally valid spatial metaphor. This is especially true when also social and cultural issues of the concept "space" are taken into account: most spatial metaphors today (and also most metaphors discussed at the workshop) are quite detached from the social beings who are supposed to use them.

Spatial metaphors have to bring real advantages for the system: it is hard to sell a metaphor alone. Despite the advances in virtual reality systems, spatial metaphors are very much in their infancy. One of the conclusions of the workshop was that we should stop talking about spatial metaphors, start building and, above all, evaluating them.
---------------------------------------------------------------------------- Keith Instone / instone@acm.org / 95-01-03