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Batching and Unbatching 209
The number of items required for a batch is called the batch size. In some situations you know in advance how many of each item is required to make one item; in other situations the number of items batched depends on model factors and changes dynamically.
Items can be permanently batched together as one new item that flows through and exits the model, or they can be temporarily joined for some specific purpose and unbatched at a later point in the process. For example, two manuals could be batched with three promotional pieces and one CD to make a software package that is shipped as one product. Or a ship attempting to dock might be temporarily batched with two tugboats resources to guide it through the docking process, after which the tugboats and the ship are sent on separate paths.
Batch dialog
The Batch block has three tabs for determining when items should be batched, how many items to include in a batch, and what to do with the properties of items that are batched. The Batch and Options tabs are discussed below; options in the Properties tab are described on page 213.
Batch tab
The top of the Batch block’s Batch tab has a popup menu with two options that determine how the block behaves. These are summarized below and illustrated in models later in this chapter.
• Batchitemsintoasingleitemcreatesabatch
using items on a first-in, first-used basis as
they arrive at the item input connectors. The quantity of items required from each input is entered in a table or (if this choice is selected on the Options tab) determined by the value at a BatchQuantityIn connector.
• Match items into a single item creates a batch of items that have a common attribute value. For instance this could represent a process where items were combined together based on a serial or order number. For this choice, it doesn’t matter which input connector the items arrive from.
The table in the Batch dialog is for entering the number of items from each input that are required to make a batched item; the size of the batch can also be set using value input connec- tors as discussed later in this chapter. The first column shows the block label or name the input is connected to. The Quantity column is for specifying the number of items required from the input and the next column reports the number of items available. Checking the fourth column determines if Delay Kit is activated; as discussed on “Delaying kits” on page 215, this causes the specified item or items to not be pulled into the block until certain conditions are met.
Options tab
Among other choices, this tab has options for setting the size of a batch through value input connectors and determining when to start a batch.
Batch tab in Batch block
Discrete Event

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