Factores que pueden impedir una comunicación exitosa

Based on the considerations made, this paragraph proposes two techniques which were developed in the course of this work that combine both drawing a viewer’s attention to certain regions and providing information about the associated metadata.

The Informative Cursor

Informative Cursor is an approach which has not been implemented so far. Simple proto- types of the Informative Cursor are mouse cursors that change their styles to indicate that a certain action can be performed (e. g., hand cursor over Web links) or that the computer is busy (e. g., sandglass cursor). Informative Cursors can be regarded as extensions of those traditional cursors. Besides signalizing the current position of the input device, which is a cursor’s original function, Informative Cursors provide four other kinds of information:

1. Regions with metadata. The shape of the cursor consists of two arrows (see Fig. 6.4). Each arrow points at a region which is associated with metadata. The length of an arrow corresponds, inversely, with the relative distance to the nearest region. That is, if one of the two arrows is longer than the other, the region pointed at by the longer arrow is closer. While moving the cursor, the arrow lengths change smoothly but are kept within a certain margin (see Fig. 6.4(a)).

2. Amount of metadata. The amount of metadata associated with a region is ex- pressed by the thickness of an arrow (see Fig. 6.4(b)). This amount increases with the number of bytes that represent the metadata. Hence, more words, a larger image, or a collection of differing metadata types yields a thicker arrow.

6.2. Guiding a Viewer’s Visual Attention 115

3. Type of metadata. Types of metadata which can be expressed by the cursor are text, image, sound, or a combination of them. A symbol, which is the initial letter or an 0A0 in case of any combination (see Fig. 6.4(c)), is mapped as hint onto the arrowhead.

4. Accordance with interests. The accordance of the metadata’s content with inter- ests a user had specified before can be gathered from the gray shade of an arrow (gray shades can express quantity better than color [Tuf01]). The darker an arrow, the more contributing is the metadata (see Fig. 6.4(d)). However, deciding whether one por- tion of knowledge (viewer’s interests) correlates with another portion of knowledge (metadata’s content) is a very difficult task and no issue in this work. Hence, it is assumed that another system provides those levels of accordance.

Figure 6.4: Illustrations of Informative Cursors whose sizes can be compared with those of traditional cursors. The lower row shows their extremes: (a) longest and shortest, (b) thickest and thinnest, (c) character types, and (d) darkest and brightest.

The two images in Figure 6.5 illustrate the use of the cursor. In those images, there are two regions with metadata associated which are situated in the cursor’s neighborhood. Those regions show one of the daisy blooms (Region 1) and a part of a dandelion leaf (Region 2). Two conditions are assumed: (1) Region 1 is associated with an image as metadata and Region 2 has corresponding text. (2) There is a higher correlation between the viewer’s interests and the metadata of Region 1.

In the first image, the cursor is closer to Region 1, which is signalized by the differing lengths of the arrows that point at the regions. In the second image, it is vice versa. The widths of the cursor’s arrows give hints regarding the amounts of metadata. Obviously, Region 2 has, in terms of data bytes, less metadata than Region 1. What can also be observed is that the region being closest to the cursor is emphasized by highlighting its contour. The viewer can thus quickly reach the region and demand the metadata. Once the mouse cursor is over a region, its shape is changed to that of the standard cursor.

Nevertheless, there are special cases that need special handling. Examples are two nearest regions being situated in the same direction or two regions that have exactly the

Figure 6.5: Images in which Informative Cursors are used.

same distance from the cursor. Solutions can be to hide one of the two arrows (1st example case) and to choose the region whose metadata corresponds more with the viewer’s interests (2nd example case).

The proposed technique is not intended for exploring all the regions in an image which have metadata. For such a purpose, overview information would be necessary that facilitates navigation. The proposed technique rather aims at viewers who spot interesting features in an image, head for those regions, and, finally, request further information if available. Compared to the arrow metaphor exploited in Figure 6.3, Informative Cursors have var- ious advantages the most important of which are: they occlude less context information, they provide information about the metadata, and the extent of regions being focused is indicated.

Even though more stylistic features could be employed for communicating information with Informative Cursors (e. g., background color, texture, etc.), it would not necessarily contribute to augmenting comprehension. Tufte states in this regard:

“The danger of multifunctioning elements is that they tend to generate graph- ical puzzles, with encodings that can only be broken by their inventor.”

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Meta-Previewer: Exploiting the Magic Lens metaphor

Meta-Previewer is a tool that displays both locations of all regions which have metadata associated and information about the metadata associated with a focused region. It follows the idea behind Magic Lenses since the data which is displayed by the Meta-Previewer differs from the original visual data underneath.

The Meta-Previewer has a rectangular shape whose extent correlates with the size of the visualization to which it is applied. The data displayed by the previewer is split in two components (see Fig. 6.6):

1. Background area with region markers. The background area consists of a down-scaled copy of the visualization into which markers are integrated that indicate the locations of augmented regions. A certain region of this background area—the focused region— is magnified by distortion (compare with Fisheye views, e. g., [LA94, CM01, GS03] and non-linear magnification [KR97]).

2. Frame with information about the metadata. The background area has a frame that displays information about the metadata. Similar to the Informative Cursor, it includes information about the metadata type and amount as well as information about the accordance with the viewer’s interests. Values are expressed by variable bars.

The Meta-Previewer can be moved across the visualization. Figure 6.6 illustrates a po- tential scenario in which the previewer’s initial position is at the bottom of the visual- ization. Which region is focused by the previewer depends on its position relative to the visualization. In the figure, the initial focal region is the region around the dandelion leaf, which yields this region to be magnified by the Meta-Previewer. When the Meta- Previewer is moved towards the dandelion bloom, it changes its state, which is illustrated in Figure 6.6(a)–(d):

(a) The visualization is copied and region markers are inserted. Region markers are small spheres which were designed with the objective of quickly attracting a viewer’s attention. The markers’ locations are the centroids of the corresponding regions. Besides serving as identifiers, those markers can also be selected to request the actual metadata.

(b) The augmented region which is closest to the center of the Meta-Previewer (the focused region) is emphasized by highlighting its contour.

(c) A non-linear distortion lens is applied to the image so that the focused region is magnified. The effect is that, besides the region being focused, the region markers around the focal region are magnified whereas other markers situated in the periphery are scaled down.

(d) Finally, information about the metadata associated with the focal region is attached to the Meta-Previewer. This includes information about which types of metadata

Figure 6.6: When the Meta-Previewer is moved across the visualization, its content is permanently updated. This includes magnifying the region being focused as well as displaying information about the focused region’s metadata.

are available and what are their relative amounts (in terms of bytes). In the fig- ure, for example, there is some textual and a bit more visual information available. In addition, the accordance with the viewer’s interests (compare with the previous paragraph) is expressed by the vertical bar.

The necessity for applying a magnification lens technique follows from the down-scaled view of the Meta-Previewer. Visualization details as well as region markers would be hard to recognize without the focal regions being magnified.

The advantage of the tiny view is that only a small portion of the original visualiza- tion is occluded. To further compensate the occlusion problem, the Meta-Previewer could be displayed semitransparently. Regions of the original visualization, superimposed by the previewer, could then still be perceived at a fraction. In this regard, Baudisch and Gutwin [BG04] proposed a technique, which they call multiblending, that improves per-