Paths show the order in which the command or statement is constructed and are represented by horizontal and vertical lines. Many commands and statements have a number of options so the railroad diagram has a number of different paths you can take.
The following example has three paths:
The three paths in the previous example show the following three possible commands:
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REMOVE
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REMOVE SOURCE
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REMOVE OBJECT
A railroad diagram is as complex as a command or statement requires. Regardless of the level of complexity, all railroad diagrams are visual representations of commands and statements.
Railroad diagrams are intended to show
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Mandatory items
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User-selected items
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Order in which the items must appear
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Number of times an item can be repeated
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Necessary punctuation
Follow the railroad diagrams to understand the correct syntax for commands and statements. The diagrams serve as quick references to the commands and statements.
The following table introduces the elements of a railroad diagram:
Elements of a Railroad Diagram
|
The diagram element . . . |
Indicates an item that . . . |
|---|---|
|
Constant |
Must be entered in full or as a specific abbreviation |
|
Variable |
Represents data |
|
Constraint |
Controls progression through the diagram path |
