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The EBNF is the extended/newer version of BNF, so the problem becomes simpler: EBNF vs ABNF. I'm not an expert, but think that it should depend on a language, whose syntax you want to define. Also there are some visualizers for EBNF (http://www.google.co.il/search?sourceid=chrome&ie=UTF-8&q=Ebnf-Visualizer), but didn't see any for ABNF,