General Usability Issues

Apart from the usability issues explained above, the study revealed a couple of other problems that had impact on the usability of Interface Currents. These problems include overlapping of information items floating on a Current, the fact, that only one user at a time can interact with a Current, and some usability issues with regard to the buttons for creating new Interface Currents as discussed in the following sections.

Overlapping of Information Items

The space on an Interface Current is limited by its surrounding boundaries. Thus, when large amounts of information items are spread out on an Interface Current it cannot be avoided that they start to overlap each other. This decreases the usability of Interface Currents because the visibility of floating information is hampered. While the problem was already observed during pilot tests, it occurred in both tasks participants had to perform during the study. During the first task, information items overlapped primarily on the peripheral Current (see Figure 6.10).

This constrained participants while browsing through the pictures on the Current be- cause they could not see sufficient details. Several statements during the interview ad- dressed this problem: “That (overlapping of images) was something hard. (...) they (the images) were kind of one over another”. Some participants applied a certain technique in such situations: They successively touched the pictures floating by in order to bring them into foreground (see Figure 6.10(b)). This technique was often combined with the establishing of a magnification area on the peripheral Current that lets pictures ap- pear larger and clearer (see Figure 6.10(a)). Furthermore, participants sometimes just dragged items from a clustered part of the Current into the normal workspace in order to watch them more closely (see Figure 6.11). The functionality that lets items shift into foreground at a certain position on the Current, as described in Section 4.2.2, eased the problem a little bit as some statements show: “I did like that they come into focus. I mean, that they take the top position when they are in front of you”. However, this func- tionality seems to be too restricting to really solve the problem. It does not allow users

Chapter 6 Usability Issues

(a) Creating a magnification area on the Current. (b) Touching pictures successively.

Figure 6.10:Problem of overlapping pictures on the peripheral Current.

Figure 6.11:Taking a closer look on pictures.

to move around, for instance. Some groups did not even notice this feature at all. With regard to the problem of overlapping items, the first task revealed that users concentrate more on an whole area on the Current when they are browsing through information items floating on the Current rather than on a certain position. This has to be considered when designing solutions for this problem.

Similar problems occurred in the second task when participants were loading the con- tent of Interface Folders on Currents. Overlapping items were perceived as even more distracting than in the fist task because word tags were involved among the information items. While the content of photos was at least partly visible, participants could not read the words at all when the word tags were overlapping each other (see Figure 6.12). On the stream-shaped Currents participants used similar techniques as in the first task for dealing with this problem: They were tapping on items to bring them in foreground and they established magnification areas on the Currents. Other strategies were applied

6.1 Usability Issues of Interface Currents

(a) Overlapping word tags on

stream. (b) Overlapping word tags on pool.

Figure 6.12:Overlapping word tags are hard to identify.

when participants were working with a pool-shaped Current. When connected to a pool- shaped Current, the content of an Interface Folder gets spread out along the peripheral of the Current, as shown in Figure 6.12(b). Some participants complained about this because items could be spread out more on this area in order to avoid overlapping. In contrast, some participants liked the possibility of selecting certain items from the pe- riphery of the pool-shaped Current and bringing them into the middle (see Figures 6.13). Answering to the question of the examiner if it would be better to spread items out on a

Figure 6.13:Hierarchical arranged items on a pool-shaped Current.

pool-shaped Current evenly, one participant stated: “Maybe not. Maybe we want every- thing on the base hierarchy (the periphery of the Current) and if we want something, maybe we can just pull it out. Or if we don’t want it we can just drop it back into the base hierarchy.”. This statement shows that the overlapping or piling, in particular on a pool-shaped Current, is not necessarily problematic but also can offer new strategies for using the Current. However, working with a pool-shaped Current in such a way requires

Chapter 6 Usability Issues

the items to be visible at least so that users can decide if a particular item is worth to be selected and watched more closely or not.

In Sections 4.2.2 and 4.3.2 some solutions were discussed that can be applied to avoid the problem of overlapping information items on Interface Currents. Although these solutions are only prototypical approaches they seem to have potential. Participants pronounced similar ideas during the study. The approach of letting information items come into foreground when they reach a certain position on the Current, for instance, could be enhanced by bringing items in foreground and spread them out as soon as they reach an area on a stream-shaped Current where the width exceeds a certain threshold (see Figure 6.14). This idea is motivated by the assumption that users enlarge the parts

Figure 6.14:Bringing items into foreground based on a certain threshold.

on a stream-shaped Current that they are interested in. Other parts, at the same time, are left rather narrow in order to save space. Information items on narrow parts of a Current are hard to see anyway and, thus, it does not distract users if they are overlapping. In contrast, items in wider areas should be spread out nicely because it is very likely that users want to see items more detailed in these areas.

Another similar idea is to spread items out on certain parts of the Current that are directly defined by users. For instance, certain gestures could be developed that enable users to select groups of items on a Current that are to spread out (see Figure 6.15). Spreading out groups of items would cause other items to pile up more. In that way items on user- defined parts of the Current would be clearly visible whereas other parts would be more clustered.

Apart from the problem of overlapping items, the fact that participants could not interact simultaneously with Interface Current had a huge impact on their usability as described in the following section.

6.1 Usability Issues of Interface Currents

Figure 6.15:Using a gesture for spreading out items.

Simultaneous Manipulation of Interface Currents

In Section 2.2.2 the importance of simultaneous user interaction during co-located col- laborative work was discussed. Simultaneous user interaction should be enabled in in- teractive workspaces that are developed to support collaborative work. In the interactive workspace that was provided to participants during the study, simultaneous user inter- action was enabled. However, while users can interact simultaneously in the workspace, all interface components, such as Interface Objects, Interface Currents, and Interface Folders, can only be manipulated by one user at a time to avoid interferences between users caused by conflicting interactions. During the interaction with Interface Objects, participants did not feel constricted by this constraint because Interface Objects were usually used by one single participant at a time. In contrast, with regard to Interface Cur- rents, this restriction was causing some problems because Interface Currents are rather large and are often utilized by multiple users, such as, the peripheral Current. In partic- ular during the second task, both participants often tried to manipulate the Current at the same time. Due to the awareness function (see Section 4.2.3), participants quickly became aware of when they could not manipulate the Current because it was already adjusted by another user so their interactions did rarely conflict directly. Nevertheless, they had to wait until the partner had finished the interaction with the Current. This was often found very frustrating. In the first task, this problem occurred mostly on the peripheral Current, for instance, when both participants wanted to establish a magnifica- tion area on the Current. The second task exposed the problem even clearer. Participants often worked together very closely during this task. Usually, they first debated how the different Interface Currents should be arranged in the workspace and, after this, started to manipulate them in the desired way. Nearly every group tried to stretch Currents across the workspace in order to make them available to both users. This required mov- ing several control points of a Current. Several groups wanted to divide up this work

Chapter 6 Usability Issues

in a way that each participant would manipulate the points that are easy to reach (see Figure 6.16). Since participants could not interact with the Current both at the the same

Figure 6.16:Reshaping the same Current together is difficult.

time, this strategy did not lead to a saving of time but forced one participant to wait until the other had finished the interaction with the Current.

Simultaneous interaction with an Interface Current was disabled for the study system because it can cause conflicts when contradictory interactions are performed by users, for instance, when both users try to interact with the same control point or when they try to

use the same function (for instanceresizingorrelocating) in a contradictory way. The first

case never happened during the study probably because of the chosen user arrangement. Participants did not really share the same control points on an Interface Current and they could not reach the control points on the partner’s side easily. Furthermore, if those kind of conflicts would have happened, they would be noticed by users and could be corrected immediately. Thus, for critical functions such as resizing and relocating,

simultaneous user interaction should be disabled. In contrast, reshaping and changing

the width of a Current are functions that involve only one single control point. When these functions are performed on different control points, simultaneous user interaction should be enabled. This would avoid frustrating waiting periods for users and, in fact, enable groups to work together when establishing a workspace.

Another usability issue found during the study was caused by the buttons for creating new Currents as described in the following section.

Hindering Buttons for Creating New Interface Currents

The buttons for creating new Interface Currents were installed fixated in front of each user. This chosen position was causing problems as the study revealed. In every sin- gle study session it was observed that participants touched the buttons accidentally and, thus, produced new Interface Currents that they actually did not want to create (see Fig- ures 6.17). While this inconvenience was relatively easy to fix by just deleting acciden- tally created Currents, the position of buttons was, in addition, preventing participants from using the space in front of them for other purposes, for instance, as a personal