It would be nice to view documents in such a way that one could tell the document "I don't understand that theorem, give me a more verbose view".
Sometimes there are multiple dimensions along which views might vary. For instance, sometimes an expert mathematician may be browsing a math site, and may wish for more verbocity about a particular concept (i.e. what is it related to, etc). This is different from the verbocity that a beginner may wish for. There are really two orthogonal dimensions here; "easy/difficult" versus "summary/detailed discussion".
Technologically, this is much like MultipleViews (except that MultipleViews are qualitativly different objects, while ZoomableView?s exist in a graded continuum). However, MultipleViews connotes the idea of having qualitatively different views which may not agree with each other. In ZoomableView?s, the different views are all a part of the same "document", and express the same "viewpoint". MultipleViews is hearing different viewpoints on the same issue. ZoomableView?s is hearing different presentations of the same viewpoint of the same issue (perhaps tailored to different audiences).
Another metaphor is an "outline", which one can expand or collapse as desired to get more information on certain topics. RadioUserLand has a feature like this; see [LiveTopics] for a random example of this in action. As currently setup, there is only one "dimension" in the system, but this could easily be changed (the addition of different colored arrowheads, for example).
It would be neat to see this feature in a wiki. (FractalWiki comes to mind, though it's not the same ...)
FractalWiki may be a step in that direction; though it ain't it's purpose, the ZoomingInterfaceParadigm may be of benefit to FractalWiki ...
CategoryToDo: This page should be reconciled with ZoomingInterfaceParadigm or connected to SemanticZooming? in some way.
In UnderstandingComics?, Scott McCloud? discusses how abstracted iconic representations distinguish themselves from a detailed background. They are simpler, easier to identify with, universal, and conceptual, whereas a detailed ground depicts something real and specific, which makes it far more difficult to identify the underlying concept. I suppose the whitespace also helps separate the simpler icon from the detailed image. Perhaps it's better to zoom out on interesting features, simplifying from a dense ground of data the relevant facets to the current query.