Building a Model with Elementary Components

Modifier Component

The Modifier component assigns an attribute to a transaction. The control panel, shown in Figure 3.8, provides a field for entering the attribute name and a set of radio buttons for specifying how a value for that attribute is calculated. It can be the result of a simple character or numeric assignment, a formula evaluation, sampling of a random variable, or the value read from a variable in a data set. Regardless, the result of evaluation is the value given to the attribute. This attribute-value combination is unique to the transaction, and the transaction carries it on its route through the simulation network.

Figure 3.8: The Modifier Control Panel

By default, the value is calculated when the transaction arrives at the Modifier. However, if you select the Delay Formula Evaluation check box, the formula is not evaluated when the transaction arrives at the modifier but is itself the value of the attribute. This feature is used with the "filter" trigger message on queues.

The following documents the logic of the Modifier component.

Transaction Arrival

assigns the attribute value pair; 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 Modifier is busy, then return TRUE; else, return FALSE.

Query Message

Trigger Message