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I have seen a lot of these diagrams in some help files and src documentation

What are they called? Are there any other (for same purpose) known diagrams?

enter image description here

Img source : http://www.sqlite.org/images/syntax/insert-stmt.gif

Hernán Eche
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    [This question](http://stackoverflow.com/questions/796824/tool-for-generating-railroad-diagram-used-on-json-org) has some more details on railroad diagrams, including a few links to some generation programs. – whatsisname Jun 02 '11 at 15:42

2 Answers2

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They are called "railroad diagrams", because of their resemblance to a railroad track. They were often used to describe the grammar of older languages, before more formal grammars became routinely used. The problem with them is you can't easily feed them into tools like parser generators, or grammar checkers, so they are not used so much these days.

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They are called syntax diagrams.

Howard
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