Visio pages and ORMSware networks
ORMSware facilitates rapid quantitative modeling using hierarchical logical networks. Putting together
hierarchical logical networks is made possible through objects in a Visio stencil
we have developed for ORMSware.
First page in any Visio interface file of an ORMSware
model must always be the top level network of the model. Each subsequent page,
if any, should contain one [sub]network. Any network (i.e. page) in a Visio file
can reference any other network in that file.
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Network referencing mentioned above is accomplished by defining the Type property
of an appropriate node in the referencing network to be of Network type.
Figure 6 shows how the Type property of n[2] in the example problem in Figure 1-Revised window
(click here if it is not
open) has been changed from Normal to Network.
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Figure 6 |
When a given node is of Network Type, NMOD expects to see a
page with the same name as that of the Network node in the model's
file. In the case of Figure 6 showing a Network node in our
example model, NMOD will expect
to see a page with the name PiecesPerHour in the model file.
Close Figure 1-Revised window and click Figure 6 (if it is not already open) to open a separate window displaying an
expanded version of our example model.
Click the PiecesPerHour tab at the bottom of the window. Your browser will display the
PiecesPerHour network.
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Note:
You will get hands-on look at how all of this works in Visio if and when you go
through the hands-on tutorial. |
Looking at the Type property of node 3 (n[3]) in
PiecesPerHour network, notice that it says "Start Node." Every network
must have one, and only one, Start node. When NMOD starts execution of a model,
it looks for the Start node in the top level network (page 1) of the model's
file. When execution thread reaches a
Netwok type node ([2]PiecesPerHour in this case) in the top network, ORMSware transfers
execution control to the
Start node of the PiecesPerHour network.
Every network that is referenced in another
network must have at least one Return node if control is to be returned to the
referencing node when execution of referenced network is finished. Notice that PiecesPerHour network
has one Return node. It is n[4]PiecesPerHour. When NMOD finishes execution of
n[4], it returns control to the node in the referencing network which evoked
this network (i.e. PiecesPerHour.[2]CostPerPiece
in the case of our
example model).
Networks can be referenced recursively. There is nothing an analyst has to do
to communicate to NMOD that recursive referencing will be used. The depth of network
references,
recursive or not, is limited only by memory available in the computer on which
the model is executing.
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Note:
You may have noticed that we changed CostPerPiece network while
expanding the model. We inserted a Start Node (n[6]Initializations) into
the network and introduced Support arcs [11], [12], and [13] leading out of it to
n[2], n[4], and n[1] respectively. We did this, because at this
point we are moving from just discussing concepts to developing a working
model of our [hypothetical] production situation. We will explain shortly
why these arcs are necessary. |
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