In this chapter we will walk you through the creation of a sample temporal constraint network. In the process, you will begin to become familiar with many of the important features of Tachyon.
If you are using X11:
From an Xterm prompt type xtach then press return. Tachyon does not need any startup parameters.
(See also ``Using the Master-Script'')
At this point, Tachyon's graphical user interface appears, and you can create a new temporal constraint network or reload a network created previously.
To familiarize yourself with the process of editing an existing temporal constraint network, you can use any of the sample networks in the Tachyon samples directory. We will use the Beatles network here.
Figure 3.1: The File Open Dialog Box
For more information about Events/Nodes see Section ``Using the Graphic Interface''
You may now continue modifying events and solving the network using steps 6 - 10.
If you would like to change the color combinations refer to ``Configuration: Colors''
A temporal constraint network consist of a set of events and a set of constraints which affect those events. An event is any activity which consumes an amount of time. For example, 'Loading a truck' is an event.
For our first network we will create two events and a single constraint between them. This network will be used to design a 'widget'.
To create your first event, position your mouse on the Tachyon canvas. Press SHIFT+LEFT MB. An unnamed and unconstrained event (node) will appear where the mouse was positioned. The figure below shows the Tachyon user interface and the event that you should be seeing.
Figure 3.2: The Unnamed/Unconstrained Event
Double-click on the event (node). A Node Information Dialog box will appear which describes the event and allows you to modify the values.
Rename the node to something meaningful such as ``Write Widget Specs''.
Notice that the default time format is days (bottom right of Tachyon window). We will not change it for this example.
Next, do the following:
Create a second node (SHIFT+LEFT MB), and:
For more information on the capabilities of the node dialog box see ``Node Information Dialog Boxes''.
The next step is to create a constraint between these two nodes. Position the mouse pointer onto the ``Write Widget Specs'' node. Press SHIFT+LEFT MB and keep it down while positioning the mouse pointer onto the ``Build Prototype'' node. Release the keys and the mouse button . At this point a constraint arrow (edge) will appear.
Double-click on the arrow. An Edge Information Dialog box will appear which describes the event and allows you to modify the constraint values.
Selecting both ``Before'' and ``Meets'' creates a constraint between the events
``Write Widget Specs'' and ``Build Prototype'' that is satisfied only if
``Write Widget Specs'' is completed before or at the same time as ``Build
After the ``Display'' cycle button was pressed the ``Display Relation'' should
have appeared. This function controls whether or not the constraints label is
displayed on the arrow.
For more information on the capabilities of the node dialog box see
``Edge Information Dialog Boxes''.
Now you have a very simple temporal constraint network. The next task that
needs to be completed is to solve the network.
For more information on 6-tuples, 8-tuples and Allen relations, see documents
referenced in the Bibliography
If you were unable to complete this example network, please refer to
(c) 1996 General Electric Co.