HUMAN-COMPUTER INTERACTION
SECOND EDITION
HUMAN-COMPUTER INTERACTION
SECOND EDITION
Describes generative transition networks, a form of state transition network which has many features of an event-based production system. In particular, it attempts to solve some of the problems that STNs have with concurrent dialogs.
When we discussed the WIMP interface as an interaction paradigm in Chapter 4, we pointed out its ability to support several separate user tasks simultaneously. Windowing systems provide this capability by sharing the resources of a single hardware configuration with several copies of an abstract terminal. Each abstract terminal will behave as an independent process and the windowing system will coordinate the control of the concurrent processes. To ease the programming task again, this coordination of simultaneously active processes can be factored out of the individual applications, so that they can be programmed as if they were to operate in isolation. The window system must also provide a means of displaying the separate applications, and this is accomplished by dedicating a region of the display screen to each active abstract terminal. The coordination task then involves resolving display conflicts when the visible screen regions of two abstract terminals overlap.
Scope Finally, the designer must consider the scope of the help: is it to be offered at an application level or system wide? The latter may be the ideal but is much more complex. If users are to be modelled at a system level the model should take into account the levels of activity in which they are engaged and be able to distinguish actions at an application level. In many systems it would also have to cope with interleaving of activities and concurrent execution. Each of these makes the modelling activity more complex.
If we consider synchronized systems, then the actual time of use becomes more important. If the participants are operating at the same time (concurrent access), we have real-time interaction as seen in meeting rooms (co-located) or video conferences (remote).
Alternatively, the system may prevent users working at the same time, by large-scale locks, leading to non-concurrent synchronized working. Earlier argumentation tools fall into this category. Because the participants are forced to use the system one after another, we can call this serial access.
Finally, co-authoring systems like Quilt [137] allow fine-grained locking so that participants can use the system at the same time or not. Therefore, they allow both serial and concurrent synchronized access.
processed in 0.002 seconds
|
| |
|
HCI Book 3rd Edition || old HCI 2e home page || search
|
|
| feedback to feedback@hcibook.com | hosted by hiraeth mixed media |
|
| |