Building a Model with Elementary Components

MultiTrigger Component

When a transaction arrives at a MTrigger component, it initiates the sending of a set of messages to a set of components, one message to each component. For example, Figure 3.7 shows the control panel for a MTrigger component.

Figure 3.7: The MTrigger Control Panel

Notice that the Triggers list box contains two entries, one labeled Server -> preempt and the other labeled Trigger. The first one indicates that an arriving transaction will cause the "preempt" message to be sent to Server. The second one, labeled Trigger, has not been specified but is selected. Selecting this and pressing the Edit button raises the second window which looks like the Trigger Control Panel. Notice that the Server named Server is selected in that window. Also notice that seize has been selected. This means that the second message triggered by an arriving transaction will send the "seize" message to the component labeled Server.

The following documents the logic of the MTrigger component.

Transaction Arrival

sends each message to the appropriate component, then the transaction flows down each arc directed away from the component.

Request for Transaction

The request is sent up each arc directed into the component.

Are You Busy Message

If any of the components on arcs directed out of the MultiTrigger is busy, then return TRUE; else, return FALSE.

Query Message

Trigger Message