Database Reference
In-Depth Information
1: SICK
90
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Fig. 1.16
create the simplest model that answers the questions you posed before you began!
Otherwise, you will likely be adding unneeded complexity (and valuable effort and
processing time) to your model.
As the model grows, it will contain an increasing number of submodels, or mod-
ules. You may want to protect some of these modules from being changed. To do
this, click on the “Sector” symbol (to the left of the “A” in the next set of pictures)
and drag it over the module or modules you want to protect. To run the individual
sectors, go to “Sector Specs” in the RUN pull-down menu and select the ones that
you wish to run. The values of the variables in the other sectors remain unaffected.
By annotating the model, you can remind yourself and inform others of the as-
sumptions underlying your model and its submodels. This is important in any model,
but especially in larger and more complicated models. To do this, click on the “Text”
symbol (the letter A) and drag it into the diagram. Then type in your annotation.
Notes can be left in the graph as well. Just click the “?”.
The tools mentioned here are likely to prove useful when you develop more com-
plicated models and when you want to share your models and their results with
others. STELLA contains many helpful tools, which we hope you will use exten-
sively. You will probably want to explore such features as “Drill Down” (visual
hierarchy), “Space Compression,” “High-Level Mapping Layer,” “Arrays,” and the
“Authoring” features of STELLA. The appendix provides a brief overview of these
and other features.
Make thorough use of your model, running it over again and always checking
your expectations against its results. Change the initial conditions and try running
the model to its extremes. At some point, you will want to perform a formal sensi-
tivity analysis. The excellent sensitivity analysis procedures available in STELLA
are discussed later.
