Interaction techniques

Having looked at available layout techniques in section 3.1, the various interaction

techniques used in the design work presented in this thesis are now introduced and their

advantages are evaluated.

3.2.1 Dynamic querying

The development of dynamic querying was an attempt to improve on the standard

database search interfaces. In a dynamic querying interface the results are presented

visually and the database is searched by visual manipulation of the query components.

The results are rapidly (< 100ms) displayed so as to give the user reversible, incremental

control of a query (Shneiderman 1994). When compared to natural language and paper

based interfaces, users answered queries faster with, and gave higher subjective ratings to, a dynamic query interface (Shneiderman 1994). This kind of interface lets users

interactively explore multidimensional databases and discover trends, clusters, gaps and outliers.

3.2.2 Tightly coupled displays

This ubiquitous technique involves the dynamic linkage of multiple views of the same

data. Perhaps the oldest application of this idea is in scatterplot brushing (Becker &

Cleveland 1987); points on one scatter plot (say film revenues vs. date) are selected and the sampled data points are highlighted on another, related scatterplot (say rainfall vs.

date). Brushing allows the user to explore multiple facets of particular portions of large data sets.

Another important application of this technique is in the provision of overview maps

which link to a window providing a detailed view, a technique called overview+detail.

Chapter 2 section 3 59

provide access to large tree structures through an overview w indow show ing the entire tree, and a detail w indow in w hich the node labels can be read (see Figure 6) (Kum ar, Plaisant & Shneiderm an 1997). D ynam ic queries can then be constructed w hich grey out the unw anted portions of the tree in both views. A w ire fram e box in the overview w indow , the panner, determ ines w hat is seen in the detail w indow . So, if all the m aterial

currently in the detail view has been greyed out, the panner can be m oved to bring the areas not greyed out by the dynam ic query into view.

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Figure 6 PDQ Tree-browser (Kumar, Plaisant & Shneiderman 1997)

North and Shneiderm an report an em pirical exam ination o f the effect o f coupling overview +detail displays o f a large docum ent (North & S hneiderm an 2000) (see 3.2.3 for m ore on overview +detail). There w ere three conditions: a single ‘d e ta il’ view with the entire docum ent in a scrolling w indow , the detail view w ith an overview w indow show ing the section titles, and detail and overview w idow s coupled so that selecting a

heading in the overview w indow scrolls the detail w indow to the corresponding section. The experim enters found that the uncoupled overview was only faster on tasks that required participants to find overview inform ation, but w hen coupled with the detail w indow it proved to be on average 80% faster for search tasks. This shows that the com bination o f tight coupling and overview +detail displays can deliver substantial

im provem ents in navigation perform ance. [ Fisheye A I fruvw l F a-htcn kOl r r e o A g o n l Free Merchant B u s i n e s s F re e S ho p Furniture Garden Gateway 2000 C Georgia Tech D Google Search E Guru Net f HiFi G B

3.2.3 Focus + context displays

M any m ethods have been developed to provide

single view s w hich sim ultaneously preserve

overview w hile giving access to detail.

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P ICQ Online Com m unication y Info Space

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Spence and A pperly developed a focus+context visualisation, nam ed the bifocal lens, for using and locating inform ation in the w orkplace (Spence & A pperly 1982). Furnas generalised this technique calling it a fisheye view (Furnas 1986). This m ethod is based on the creation o f a level o f interest m etric and m anipulation of the objects in the display to em phasise objects w hich score highly. The degree o f interest m etric is calculated as the sum o f an a priori m easure o f im portance and the distance from the point o f interest. F or indented program listings, im portance is based on how indented the text is and, the distance, is calculated as the num ber o f lines aw ay from the point o f interest. A sim ple algonthm can be used to om it lines with a low degree o f interest, preserving all the code

Figure 7 The fisheye menu (Bederson 2000)

Chapter 2 section 3 61

at the point of interest, but only the programs skeleton on either side of this point (op.

cit.). This principle has been applied in many visualisations (Leung & Apperley 1994).

Recently, the fisheye technique was applied to the pull-down menu widget and provided

satisfying and rapid access to items in long menus (Bederson 2000) (see Figure 7)