Page 41 - ExtendSim User Guide
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Model basics
In the simplest terms, ExtendSim models are made up of blocks and connections. The Reser- voir model, for example, has five blocks, as you can see in the model window. As the model runs, information goes into a block, is processed and/or modified, and is then sent on to the next block via a connection.
Blocks
Running a Model 15
Model basics
Input Output
connector connector Block
Block Connection
Each block in ExtendSim represents a portion of
the process or system that is being modeled.
Blocks have names, such as Math or Queue, that
signify the function they perform. A Queue block,
for example, will have the same functional behav-
ior in every model you build. You can also add
your own label to a block to indicate what it represents in your specific model, such as a Queue block labeled Waiting Line.
☞ Blocks are stored in Libraries. You will learn more about libraries and how to access blocks from them at “About libraries” on page 26.
Most blocks are composed of an icon, connectors, and a dialog.
Icons
A block’s icon is usually a pictorial representation of its function. For instance in the Reservoir model, the block labeled Reservoir is a Holding Tank block. Its icon symbolizes an actual tank that can have quantities added or removed from it. The small squares attached to the sides of the icon are connectors, which are discussed in more detail in the following section.
☞ Place your cursor over a block’s icon to see a Tool Tip with its number (a unique identifier based on when the block was placed in the model), block name, and the library it comes from. To also display a description of the block, go to Edit > Options and check Include additional block information in the Model tab.
Connectors
Most blocks in ExtendSim have input and output connectors (the small squares attached to the block). As you might expect, information flows into a block at input connectors and out of the block at output connectors.
A block can have many input and/or output connectors; some blocks have none. For instance, the Holding Tank block labeled Reservoir has an input connector on the left for values to enter. The output connector on the right reports the results of the block's computations; in the tank it reports the contents at each time step. Additional inputs on the bottom are for controlling spe- cific tank behavior.
The function of a connector is specific to the block; you can get information about a connec- tor’s function by clicking the Help button in the bottom left-hand corner of the dialog, as dis- cussed in “Dialogs”, below. Since connectors are more important when you build a model (as compared to when you run it), they are discussed in more detail in “Connecting blocks” on page 28.
Parts of a model
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