TRANSPORTADORES QUE INTRODUCEN METALES EN EL CITOSOL.

Most research contribution relating to the design implications of space-related issues address only one or two of the object attributes discussed above (location, orientation, ownership, and scale). Nevertheless, the findings and recommendations presented can be generalized to apply to all the attributes. For example, many of the design recommendations regarding orientation also apply to location, ownership and scale, and so on. For this reason I have chosen to group all research concerned with such space-related issues into one section and, in some cases, traded being specific about what each paper targets with unifying the findings and recommendations to present them in a more useful form.

Proposed design guidelines for supporting territoriality and different object attributes are di- vided into system level and territory level guidelines. On the system level (Scott, 2003; Kruger et al., 2003), systems must allow for

• free and lightweight techniques for the adjustment of territory sizes, default attributes, and attributes of items regardless of the default value,

• easy override of default actions associated with each territory, and

• the provision of clear feedback of actions.

At the territories level (Scott et al., 2004), territories should provide

• visibility and transparency of action (i.e. in contrast to using laptops as personal territories),

• functionality in the appropriate locality, and

Kruger et al. (2003) in their investigation of the issue of orientation, made the important ob- servation that only slightly more than half the rotations resulted in alignment with the general orientation of the associated territory, and the remaining rotations were arbitrary. Generalizing, this suggests that if a system supports automatic settings for objects’ attributes depending on their location, it must also allow for easy lightweight override of this automatic behaviour.

Shen et al. (2003) and Scott et al. (2004) discussed the issue of ownership and access rights of objects. Shen et al. suggested three modes of object sharing: private (not visible, not accessible), personal (visible, not accessible), and public (visible and accessible). The original owner of the document should maintain explicit control about distribution and replication of the document even when it is placed in the public space. The system should make such ownership information clearly visible. The ownership attribute is rather different from location, orientation, and scale, in that it is not an inherently observable attribute. Providing explicit ownership information on tabletop content can provide context by increasing awareness about others contributions. When moving an object between territories, it is desirable to be able to set whether the object’s accessibility is changed, or whether a copy of the object should be created. Adding such options, consequently, may interfere with the fluidity of collaboration due to the extra actions required to specify the required setting. The issue of fluidly changing the different attributes of objects while moving them between tabletop territories is the subject of Chapter 3, where the Attribute Gates interaction technique is proposed as a solution.

The importance of being able to fluidly change the access rights of documents was emphasized by Ringel et al. (2004) who proposed four techniques: release, relocate, reorient, and resize. The release technique is based on the timing of holding and releasing a document between two users. For the relocate technique the document’s access rights change with changes in its location between personal and public spaces; for reorient it depends on its orientation on the table; and for resize it depends on its size with the accessibility changing from personal to public when the size of the document increases above a specified threshold. A user study showed that the relocate technique was both the most efficient technique and was perceived to be the easiest to use. This finding can be extrapolated to hypothesize that relocate could be a more efficient way to control the other attributes of orientation and scale depending on the settings of the targeted territory. This is, to a certain extent, what Vernier et al. (2002) suggested in their work on visualization techniques for circular tabletop interfaces where they gave a number of suggestions regarding orientation and scale. For orientation they worked on two levels, a global level at which all the table space is rotated, and a document level at which individual documents can be rotated automatically as they are relocated either in the direction of the centre of the table, or to face a certain magnet point. As for scaling, they proposed two modes depending on whether users are working independently or are sharing objects: a central focus mode for sharing where documents are larger in the middle and smaller at the edges, and ablack holemode for working independently where documents get smaller the closer they get to the middle of the table.

Other research on tools has sought to resolve issues related to managing space coordination, and attribute settings of groups of objects simultaneously (Storage bins (Scott et al., 2005), Table- Trays (Pinelle et al., 2008) , and interface currents (Hinrichs et al., 2005)). These three techniques allow for adding/removing items, and for manipulating the location, size, and orientation of the container region. They help in managing the space by allowing for partitioning the workspace and reducing clutter; and help in coordination by facilitating group interaction, and sharing and access of resources. Interface currents were intended as group or storage spaces, and were principally de- signed to solve the problems of reach, access, and sharing of objects by providing regions (pools) or paths (streams) that rotate/flow in a controlled speed and direction (similar to Lazy Suzan ta- bles and conveyor belts). Storage bins are similar to pool shaped interface currents. They have the ability to change their shape, but without the flow effect, and are basically aimed to provide mobile storage mechanisms. TableTrays, on the other hand, have fixed rectangular shapes and, in addition to providing storage, provide more functionality by allowing cut/copy/paste operations that enable the transfer and replication of contents. All of these techniques were found to be useful in facilitating task coordination and group interaction, managing the workspace, reducing clutter, and easing access and sharing of resources. The three techniques addressed the issues of orienta- tion and scale differently. For example and with regards to rotation, storage bins used the rotate and translate mechanism (Kruger et al., 2005), interface currents depended on the flow effect for orientation, and TableTrays supported rotation by twisting the stylus around the z-access. Storage bins and interface currents automatically resized contents when dropped inside them, while Table- Trays depended on manual resizing and provided an option to restore the size of an item that had been manually resized while in the tray to its original size when taken out of the tray.

Another important issue that is related to utilizing table space and the location of objects on that space is the placement of controls (such as menus and buttons) on the table, and whether these should be centralized and shared in the public space or replicated for each user (Morris et al., 2006b). Using a picture labelling application in two modes, one that used centralized polar menus in the public area and another that used replicated copies of rectangular menus placed on the edges of the table in front of each of four users, Morris et al. found that users overwhelmingly preferred the replicated controls over the centralized ones. Two explanations for this were sug- gested, firstly, that users showed aversion to the physical proximity with team mates’ hands that the shared centralized design imposed (Ryall et al. (2006) also reported that people using direct touch tables showed concerns about their arms or hands accidentally bumping with one another), secondly, users had a preference to leave the central area of the table clear for other collaborative tasks rather than filling it with controls. Based on these findings, and the type of task involved, it was recommended that applications should provide a set of controls for each user, and that these controls should be placed on the edges near the user if possible, or allow for controls to be moved as the user requires. This recommendation, assumed users working from fixed positions, yet for mobile users, a contextual-menu, or a centralized menu option would seem to be more appropriate.