Page 292 - ExtendSim User Guide
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Resources and Shifts
Resource requirements
Choices for the Quantity clause
The quantity is entered using a popup menu at the right of the SELECT button, shown in the screen shot above. As seen in the screen shot to the right, the choices for popup menu are:
• All the resources
• A quantity determined from a named attribute
• Aquantitythatisuser-input
Unless it is limited by a WHERE clause in the quantity expression, the selected number of resources will be drawn from all the resources in the Advanced Resourcess’ Resources table.
Choices for the Order By clause
Ordering the resources is optional. If chosen, any one of the resource properties listed on page 258 can be used to sort the resources. The resources at the top of the sorted list will be used first.
The default is that an ascending value of utilization is used to sort the resources. This causes resources that are being utilized the least to be selected first.
Creating a quantity expression
On the Requirements tab, check the Create/modify quantity expressions frame to enable it. Then either choose an existing quantity expression from the popup menu and modify it or cre- ate a new quantity expression.
To create a new quantity expression:
First determine if the expression should start with all the resources from the Resources table or only a specified number of those resources (see “Choices for the Quantity clause”, above).
Also decide if the resources should be sorted by a property (see “Choices for the Order By clause” on page 266). Resources at the top of the list will be chosen first.
Then click the SELECT button to place the quantity in the expression area.
At this point, the quantity expression requires a specified quantity (all or a number) of resources. However, the collection of resources is all the resources in the Resources table of the Advanced Resources database. In complex models, that could mean a very large number of resources.
☞ In models with large numbers of resources, it will speed simulation run times if the first part of the expression uses a filtering condition that limits the search area to a pool or group.
To narrow the search area, click the WHERE operator. Then insert a filtering condition; typi- cally this would be a resource filtering condition that references a Pool or Group (for example, Property: Pool = Pool 2).
To use additional filtering conditions, use the AND/OR operators in conjunction with grouping parentheses. The result is displayed in the expression area.
☞ See below if group filtering conditions are used.
Discrete Event

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