# Appendix A - The Message Poster

Purpose: The software's message posting capability serves two purposes. First, message posting gives you, as model author, power to provide consumers of your models with visceral, concrete manifestations of model output. Second, message posting gives you a mechanism for coaching model consumers toward a deeper understanding of model structure and behavior. Message posting achieves these purposes by displaying author-defined messages (text, pictures, movies, and sound). You can even use message posting to navigate the user to a sequence of coaching screens!

Basic Operations: Message posting is activated from within the modeling mode dialog of stocks, flows and converters. A click on the "Message..." button within the dialog will take you to the message threshold dialog, as shown in Figure 4-40.

Figure 4-40 Message Threshold Dialog

Your job in the message threshold dialog is to establish thresholds for message posting. A threshold is a value for a model variable which, when crossed, will cause a message to be posted. To establish thresholds for message posting, follow the procedure outlined below.

1. Establish the range. Type numbers in the minimum and maximum boxes, as indicated in Figure 4-40. Thresholds will fall in the range between the minimum and maximum values that you set.

2. Set a threshold. Select the default tab, or create a new tab by clicking somewhere in the tab-embedding rectangle. Then, move the tab to a position that reflects the desired threshold. Alternately you can set the threshold value directly by typing in the Threshold box.

3. Set the message direction. Use the radio buttons to determine whether a message will be posted (a) when the magnitude of the variable grows larger than the threshold; (b) when it falls below the threshold; or (c) both when it exceeds and when it falls below the threshold. Note that the variable must cross the threshold for a message to be triggered!

4. Assign the message. Double click the tab to enter the message assignment sub-dialog. As shown in Figure 4-41, a plethora of features await you there.

Figure 4-41 Message Assignment Dialog

Note on Message assignment: When a tab contains multiple message pages, the pages will be accessed in order, until they have all been accessed. After all pages have been accessed, the tab will stop generating messages. To reset the tab's internal counter, simply close and re-open the model.

During the simulation run, any variables that have been outfitted with message posting capability will "post" their assigned messages, play their assigned sounds, or navigate to their assigned location upon satisfaction of their specific posting condition(s). All visible messages will be posted in the same place-in a message posting window that floats above the model surface. [Note: If you assign Sound only, the model will pause and play the sound, but no visible message box will appear.] Figure 4-42 details the salient features of the message poster window.

Figure 4-42 Floating Message Posting Window