Navigation in Hyperspace and Cognitive Representation

Lambert Schomaker, 8 Dec 1994

One solution to this problem is the visualisation of document structure as proposed by Shneiderman [1]. He proposes a number of tree visualisation techniques (Tree-Maps). By making graphical objects in such a tree clickable, the static tree image representation turns into a dynamic tool. As Balasubramanian points out,

"Graphical browsers help reduce disorientation by providing a two-dimensional spatial display of the hypertext network. They also help minimize cognitive overhead by showing a small part of the network. They also provide an idea about the size of the network which help users estimate the number of nodes and links in the system."

There are basically two approaches in visualisation:

1. The provider of the hypermedia document creates the graphical representation of the message structure herself

2. An algorithm is used to analyse an ordered list of links, e.g., the recent navigation history, followed by subsequent automated visualization

The problem with the second approach is that it is unclear whether it is at all possible to infer the conceptual (semantical) structure from physical, temporal link order. A similar problem exists at the syntactical level, in the case of automatical grammar inference. Examples of automatic visualization are the WebMap program by Peter Dömel, and a Perl program by Paul Harrington, using the automatic 2-D layout system for undirected graphs Neato by Stephen North from AT&T.

The SGI File System Navigator (fsn) demo program (known from the Jurassic Park movie), is another visualisation solution where the hierarchical directory tree structure of a file system is visualized in 3D (Figure 1). Whether this actually helps the user to build up a good mental representation remains to be seen, but fsn certainly gives an interesting perspective on your own well-know directory tree. Files are 3D blocks, and the file attributes are displayed as color size, and icons (the latter on the "roof" of a file "building").

Figure 1. Example of a 3D-visualized directory structure by the SGI File System Navigator. However, hypermedia structures are not necessarily hierarchical, which makes things more complicated. For instance, Venn diagrams are only possible if there is a strict hierarchical structure (Figure 2).

Figure 3. gives an example of Venn-diagram type layout as produced by the Humanoid user interface generator.

Examples of other topologies in relation to automated visualisation of hypermedia structure can be found in the WebMap document.

Apart from visualisation, another solution often proposed is the development of improved free text search facilities. However, the risk of such facilities is that the user's mental image of the information space even becomes more cluttered, due to the distraction caused by the false hits. Probably, it is a good idea to make a distinction between "long jumps", involving such search actions, and "short jumps", in the neighbourhood of a found (conceptual) location. It is in the latter stage within a navigation process that the problem of building a structured mental representation becomes relevant.

References

[1] Shneiderman, B. (1992). 
    Designing the User Interface (p. 432).
    New York: Addison-Wesley.

Other Literature

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