Semantic Zoom

In contrast to ordinary graphical zoom, semantic zoom does not only change parameters of a graphical representation, but modifies the selection and structure of data to be displayed.

There are three basic types of zooming.

Geometric zooming allows the user to specify the scale of magnification and increasing or decreasing the magnification of an image by that scale. This allows the user focus on a specific area and information outside of this area is generally discarded. A great example is mapping software like MapQuest or Yahoo.

The fisheye zoom is similar to the geometric zoom with the exception that the outside information is not lost from view; this information is merely distorted.

Semantic zooming approaches the process from a different angle. Semantic zooming changes the shape or context in which the information is being presented. An example of this type of technique is the use of a digital clock within an application. In a normal view, the clock may show the hour of the day and date. If the user zooms in then the clock may alter it’s appearance by adding the seconds and minutes. If the user that zooms out, information is discarded with only the date remaining. The actual information did not change, only the presentation method.

[Stephens, 2003]

With a conventional geometric zoom all objects change only their size; with semantic zoom they can additionally change shape, details (not merely size of existing details) or, indeed, their very presence in the display, with objects appearing/disappearing according to the context of the map at hand.

[Boulos, 2003]

Semantic zoom is a form of details on demand that lets the user see different amounts of detail in a view by zooming in and out.

[Weaver, 2004]

Geometric (standard) zooming: The view depends on the physical properties of what is being viewed.
Semantic zooming: Different representations for different spatial scales. When zooming away, instead of seeing a scaled down version of an object, see a different representation. The representation shown depends on the meaning to be imparted.

Example: Information Maps: See a city – zoom into restaurant and see what is served there – maybe zoom based on price instead (see expensive restaurants first, keep zooming till you get to your price range).

[Watson, 2004]

Another graphical technique to balance detail and context is known as semantic zooming or multi-scale interfaces. A physical zoom, on the one hand, changes the size and visible detail of ob jects. A semantic zoom, in the other hand, changes the type and meaning of information displayed by the ob ject. Semantic zooming avoids the physical distortions of fisheye views, by using a semantic transition between detailed and general views of information.

[Modjeska, 1997]

In semantic zooming, ob jects change appearance or shape as they change size. For example a growing dot will become a simple box, then a box with a one-word label, then a box with a longer label, then a rectangle filled with text and pictures. The goal is to give the most meaningful presentation at each size.

[UMDL, 1996]

Working on the intrinsic structure of data and incorporating knowledge about its meaning (Meta data), semantic zoom adjusts the contents and density of information that is shown instead of only changing visual detail and scale.

References

• [Boulos, 2003] Maged N Kamel Boulos, The use of interactive graphical maps for browsing medical/health Internet information resources, International Journal of Health Geographics 2(1), 2003. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=149401
• [Modjeska, 1997] David Modjeska. Navigation in Electronic Worlds: A Research Review, Technical Report. Computer Systems Research Group, University of Toronto, 1997.
• [Stephens, 2003] Todd Stephens. A Passion for Metadata – An Interview with Todd Stephens of BellSouth, Wilshire Conferences, Inc., Created at: 2003, Retrieved at: November 2004. http://www.wilshireconferences.com/interviews/Stephens.htm
• [UMDL, 1996] University of Michigan Digital Library Project. Definition of semantic zooming, Created at: June 3, 1996. Retrieved at: November 2004. http://www.si.umich.edu/UMDL/glossary.html
• [Watson, 2004] Gordon Watson, Lecture Lecture 15 - Visualisation of Abstract Information. Edinburgh Virtual Environment Centre. Retrieved at: November 2004, http://www.inf.ed.ac.uk/teaching/courses/vis/lect15.pdf
• [Weaver, 2004] Chris Weaver, Documentation for Improvise, Retrieved at: November 2004. http://www.cs.wisc.edu/~weaver/improvise/architecture-patterns.html