How to Read MaxL Railroad Diagrams

The MaxL grammar is illustrated using a railroad syntax notation. The railroad diagrams illustrate all the valid (grammatically correct) statements that can be parsed by MaxL.

Anatomy of MaxL Statements
Railroad Diagram Symbols
Sample Railroad Diagram

Anatomy of MaxL Statements

A keyword, represented in plain, lower-case font, is a unit of MaxL grammar. Keywords must be entered literally and in the correct order in MaxL statements. See the examples of keywords in the following diagram excerpt:
A terminal, represented in upper-case without brackets, is replaced by values in the appropriate format as defined in the Terminals table. In the above diagram, APP-NAME and USER-NAME are examples of terminals. Each would need to be replaced with a valid name; for example, sample or user1.
Keywords cannot be used as terminals, unless enclosed in single quotation marks. For example, to delete a user named user, the statement drop user user; would return an error, but drop user 'user'; would work.
A non-terminal, represented in upper-case with angle brackets <>, is defined in an additional diagram, usually below the main diagram.

Keywords and variables on the main line are required; optional grammar is recessed. A vertical stack of words represents alternatives. Bold words indicate defaults when no word is chosen.

Railroad Diagram Symbols

	Statement begins here.
	Statement continues on next line.
	Statement is continued from previous line.
	Statement ends here.
	Alternatives: optionally select one keyword. Boldface indicates default if no selection is made.
	Alternatives: selection of one keyword is required.
	A comma-separated list of any length is permitted.
	Word is not further defined. Replace with value of format shown in the Terminals table.
	Word used in statement is further defined.
	Non-terminal used in statements is defined here.

Sample Railroad Diagram

The following diagram illustrates a variant grammar that parses the following English sentence:
"The quick brown fox jumps over the lazy dog."

Valid sentences parsable by this grammar:

The fox jumps over the dog.
Bold letters indicate a default value when no option is entered; therefore, entry of this statement would be interpreted as The brown fox jumps over the dog.
The quick brown fox jumps over the dog.
The red fox jumps over the lazy cat.
The quick brown fox jumps onto the tired elephant.