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Data Management and Exchange
Blocks for data management and exchange
• Text file
• Local table (information that is entered the block’s data table)
Read(I) and Write(I) blocks (Item library)
The Read(I) and Write(I) blocks in the Item library exchange data with an ExtendSim data- base; data is updated only when an item arrives at the block.
☞ For an example of how the Read(I) block is used, see the DB Job Shop model located at Exam- ples\Discrete Event\Routing.
Addressing the data structure
By definition Read and Write blocks are required to be interfaced to some type of data struc- ture. The pieces of information that are required to fully and properly specify where the infor- mation is to be read from or written to (the “address”) depends on the type of data structure chosen, as shown in the following table.
ExtendSim Database
File name
Database name X Table, array, or sheet X Field or column X Record or row X
Global Array
X X X
Microsoft Excel Text File XX
X XX XX
For instance, the fully specified address for accessing an Excel file would include the file name, sheet, column, and row.
Interface methods
Once you have specified a data structure type to communicate with and determined what the fully qualified address is, the next step is to determine where the data structure address is entered:
• Intheblock’sdialogorthroughvalueinputconnectorfortheReadandWriteblocks(Value library)
• Intheblock’sdialog,throughvalueinputconnector,orbyusingattributesonitemsthatpass through the Read(I) and Write(I) blocks (Item library)
Triggers
The following table indicates the mechanism that will trigger when the data is sent or received.
Connector message Beginning of run only End of run only
Item arrival at block
Read Write
X X X
X
Read(I) Write(I)
X X
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