Describing the File Formats
Describing the CSV file format in Chapter 7 was fairly simple due to the restrictions we placed on it. The most significant of these was that every row has the same logical format. We're going to allow more variation in our flat file formats. Applications that use flat files to import or export data typically support several different logical record formats and group these records into repeating units. We'll need to specify more information about the grammar of our flat files than we did with CSV files. In addition to data types and other characteristics of fields, we'll need to specify the details of all the record types as well as how the records are grouped together.
As with the CSV format, the flat file format's file description document has three major sections, each represented by an Element that is an immediate child of the root Element.
PhysicalCharacteristics: the flat file characteristics
Figure 8.2. Sample Output Flat File (PurchaseOrders.Dat)
10 20 30 40 50 60 70 80
90 100 110 120 130
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HDRBQ003 AZ999345 2002110120021115
SHPYazoo Grocers - NE Distribution Center 12 Industrial Parkway, NW
Portland ME 04101
LINHCVAN 1200000002590000000000
DSCInstant Hot Cocoa Mix - Vanilla flavor
LINHCMIN 2400000002530000000000
DSCInstant Hot Cocoa Mix - Mint flavor
HDRBQ003 AW999346 2002110120021115
SHPYazoo Grocers - SE Distribution Center Dock 37 3975 Hwy 75
Atoka OK 74525
LINHCVAN 3600000002590000000000
DSCInstant Hot Cocoa Mix - Vanilla flavor
LINHCMIN 7200000002530000000000
DSCInstant Hot Cocoa Mix - Mint flavor
HDRAY001 2002-0967 2002110920021114
SHPCorner Drug and Sundries 14 Main Street
Wichita KS 67201
LINHCVAN 2400000002590000000000
DSCInstant Hot Cocoa Mix - Vanilla flavor
XMLOutputCharacteristics: XML output characteristics, required only when converting to XML