Defining Messages for Building Blocks

Use the Message tab to alert a user to certain conditions during a simulation. When the building block's value meets a specified condition, a message will appear.

Message Types

You can present any of the following messages:

Text message
Sound
Image
Video
Navigation

Why use messages?

As the simulation progresses, you can:

Provide the user with information about model output.
Coach the user toward a deeper understanding of model structure and behavior.
Provide ongoing information as the simulation progresses by using multiple messages for a single variable.
Navigate users to a specific location in the model (for example, a sequence of coaching screens).

Message stakes

You can specify more than one messages for a given variable; each message can be triggered at a different threshold, and each stake can trigger one or mere messages of different types.

Message stakes

Message triggers are represented by message stakes. Each message stake:

Can contain one or more messages. Messages are triggered sequentially. The next in sequence appears each time the specified conditions are met.
Can contain messages of different types. For example, the first message triggered by a stake could be a text message, and the remaining messages could be sounds.
Can have its own conditions, including values and comparison conditions. (<, >, or > or <).
Can be triggered once, once per run, each time the conditions are met, or at a specified time interval when conditions are met.

Usage examples

The following messages could be defined for the same variable (which can be a stock, flow, or converter).

A message appears when the variable's value drops below 50.
A message appears when the variable's value rises above 100.
Both message stakes contain multiple messages, with a new one appearing each time the message stake's conditions are met.

Notes: All visible messages (text, images, and video) appear in a floating message window.

If you assign a sound to a text message and there is no text, the simulation plays the sound and pauses, but no visible message box will appear.

Defining Messages

To define a message, you need to complete the following:

Select a variable to attach the message(s) to.
Create one or more message stakes. Each stake specifies a trigger point for a message.
Specify a value range in which the message can be triggered, and move the stake to the correct location within the range.
For each stake, specify the conditions required to trigger the message, the message type, and the message's content.

Tip: You can suppress all message posting for a model by selecting the Disable Posters check box in Model Settings.

To define a message for a building block:

In the Stella window, select the building block (stock, flow, or converter) you want to define a message for.
Select the Message tab.
At the top of the tab, click in the message stake box to add a message threshold stake.
Use the options beneath the message stake box to define a threshold for when the message should be posted.

For example, "Post the message when the variable's value becomes > 1000." For detailed descriptions of these options, see Message Tab.
With the message stake still selected, use the options under Message Properties to select the type of message you want to appear: Text Message or Media Message.

Note: If you selected > or < in step 4, the message stake will have a double-sided arrowhead (). Each side can have a different set of messages. Click a side to highlight it, then define its message type and content.
Use the rest of the options under Message Properties to define the content of the message (text, image, movie, sound, and/or navigation). For detailed descriptions of these options, see Message Tab.
To define additional messages for the same message stake (for example, to have a different message appear the second time the message threshold is met), click the Message 1 box, then select Add New. Use the options in the Message Properties section to define the second message. Repeat this step to define more messages for the message stake as needed.
Use the options under Frequency to specify how often per simulation run the message should appear.
When you're finished defining the message stake, click , in the bottom-right corner of the Properties panel.
To create a new message stake for the selected variable, repeat steps 3-9.
To define messages for a different variable, select the variable in the model diagram, then repeat steps 2-10.

To Edit a Message

You can edit the definition of any message you've already defined.

In the message stake box, click the stake for the message that you want to edit. If the message stake has a double-sided arrowhead (), click the side you want to edit.
Edit the Message Properties for the selected message. For detailed descriptions of these options, see Message Tab.
When you're finished, click , in the bottom-right corner of the panels.

To Delete a Message

You can delete a message stake (and all its associated messages), one or more messages defined for a single message stake, or all messages defined for a variable.

To delete a message stake and all its associated messages, select the stake in the message stake box, then click the Delete button below the box.
To delete all messages defined for the selected building block, click Delete All Messages at the bottom of the Message tab.
To delete all messages for the selected variable, click Delete All Messages at the bottom of Message Tab.