Organization of information in an interface refers to the presentation of information that is visible, accessible and usable by the users. From the organization perspective, systems are classified according to the dimensionality of the space (1-, 2- , 3-, Multi-D) and the structure (unstructured, list, graph, hierarchy, metaphor) of the presentation (Figures and ). Large images and more detailed information on these systems are in Appendix .

This taxonomy discriminates the space and structure in the presentation, not that of the information . Thus, in that sense it is different from the Shneiderman's task by data type taxonomy [16]. For example, while the information on the world-wide web has inherently a graph structure, there can be three-dimensional, hierarchical and metaphorical presentations in 2-, 3-, and higher dimensions.

This taxonomy is not mutually exclusive. For example, hierarchical presentations can be included into the graph presentations. However, due to the significance of hierarchical presentations it is given separate attention. This taxonomy covers most of the existing systems. However, there are no claims that it is a complete taxonomy.

System designers typically organize information in 1-, 2-, 3-, and higher dimensional presentation spaces. Then, this presentation space is projected onto the two-dimensional display screen space. Hence, the projection transformation may yield information noise or loss depending on the dimensionality.

LifeStreams [17] provides a one-dimensional visualization of time-ordered linear stream of documents (Figure ), where users can create and query multiple substreams. LifeLines [18], on the other hand provides a timeline-style history visualization where continuous events with a duration are shown by lines and discrete events are shown by icons. In both systems information has a linearly ordered list structure. Examples systems using one-dimensional presentation spaces also include scrollbar variations [19, 20].

VOIR (Visualization Of Information Retrieval) [21] uses the newspaper metaphor as a two-dimensional presentation style for the exploration of large quantity of short, loosely related articles. Treemaps on the other hand use a two-dimensional space-filling visualization technique for hierarchical information structures based on alternating subdivisioning of the space (Figure ). In the News in the Future [22], the information landscape is a two-dimensional landscape of documents, transparently overlaid at multiple scales. The hyperbolic tree browser [23] provides an interactive visualization of large hierarchies of information represented in node-link diagrams, by mapping the hyperbolic plane onto the unit disk (Figure ). SHriMP [24] is a visualization technique for the exploration of software structures in hierarchically organized two-dimensional graphs (Figure ). Other known systems using two-dimensional presentation space are IGD [25], VIKI [26], SeeSoft [27], Pad++ [6], and Elastic Windows [15], also including most of the windowing systems currently in use.

The WebBook and the Web Forager [28] employs a three-dimensional book-desk-shelf metaphor for the organization of web pages. The Perspective Wall [29] provides a metaphor-based visualization of linear information structures such as time-ordered documents projected on a three-dimensional wall. Cone Trees [30] is on the other hand a three-dimensional visualization tool for hierarchical structures, where for each subtree the root is positioned at the apex of the cone and the children nodes are positioned along the base circle of the cone. Similarly, the Information Cube [31] is a also visualization tool for hierarchical information structures, where in this case hierarchies are represented as nested three-dimensional translucent boxes, reducing hidden object problem. The information landscape in the Harmony browser [32] provides a three-dimensional overview of documents where hierarchical document collections are mapped out onto a two-dimensional plane and the third dimension is used to encode size of the collection.

Worlds within worlds [33] is a multi-dimensional visualization technique that allows users to explore n-dimensional worlds containing functions of arbitrary number of parameters. Hierarchy of nested boxes, each containing an arbitrarily transformed heterogeneous coordinate system, are used that allow the user to view and manipulate functions.

Sun Sep 13 18:34:46 EDT 1998