This chapter introduces the Tachyon graphical user interface and Tachyon utilities. It outlines the minimum hardware and software requirements necessary to install and use Tachyon and also points out the differences between Tachyon versions 2.x and 3.0.
Tachyon requires the following minimum configuration:
1. Create a directory for Tachyon in which to install.
2. Move to this directory.
3. Type tar xvf <device> to load from the installation media.
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After Tachyon has been loaded it will be ready run. To run, type xtach. Select Quit off File menu to exit.
Sample temporal constraint networks are provided in the subdirectory /Data.
All help files are located in the subdirectory /Doc.
Tachyon 2.0 did not support graphic layout. Version 2.1 supported it in the sense that if layout information was not saved in a file, it would lay the graph out and thereafter have said information stored in the auxiliary *.net file.
Tachyon 3.0 fully supports dynamic layout capabilities, including supporting resource specification of layout preferences. Partial layout is currently unavailable.
We have also switched to a modeless interface and added some useful accelerators. For an overview of these changes, refer to Section ``Using the Graphic Interface.''
Cut and Paste features have now been incorporated into Tachyon. Currently, one can cut nodes and/or edges from the graph and paste them at a later time. In the future, when multiple graphs can be displayed simultaneously, we will provide the capability to paste between graphs.
Version 4.0 provides hierarchical collapse and multi-layer viewing capabilities. These capabilities are in ongoing development and may cause problems when used in conjunction with other features (e.g. cut and paste). This has an effect on the Tachyon file format as well.
In essence, we allow logical grouping (or parenting or abstraction) of a number of node-events into a single node. The parent or hierarchical node takes the place of the child nodes which have been collapsed into the parent. One can re-visit the detail of the child nodes by expanding the parent. The semantic rules governing this interaction are being developed in ongoing usability tests.
Tachyon offers inconsistency handling facilities capable of both detecting and diagnosing the cause of inconsistent temporal networks. Tachyon will detect an inconsistent network when asked to propagate the network's temporal constraints. This inconsistency indication will either appear as a dialog box or as a message on the message line of the Tachyon interface, depending on whether the system is being used in novice or expert mode.
If an inconsistency is present in a network, it can be diagnosed using the "Diagnose Inconsistency" menu item in the "Solve" menu. Depending on the size and complexity of the network, the diagnosis can take a few moments or a few minutes. Once complete, the set of nodes involved in the inconsistency will be highlighted in the network graph display. The user can then examine these nodes and the constraints amongst them to determine the root of the problem. If more than one inconsistency exists in the network, then the first one encountered during the diagnosis process is shown, to allow the user to correct the problem and move on to the next problem. The diagnosis algorithm could also be told to find all inconsistencies in the network, but it was determined that the average user will prefer to fix one inconsistency at a time and iterate the diagnosis process manually.
This figure (17k) shows a small network associated with a disaster relief effort. The network contains an inconsistency involving the required start times of some of its events. This figure (18k)shows the result of running the inconsistency diagnosis on this network. The events involved in the inconsistency have been highlighted, and the user can now determine that the start time requirements on these nodes are incompatible with the constraints placed between them.
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