I think there are two issues with XML/JSON/etc vs. roll-your-own format/grammar. The first issue is the difficulty of creating it, which you describe as "trivia

I think there are two issues with XML/JSON/etc vs. roll-your-own format/grammar. The first issue is the difficulty of creating it, which you describe as "trivial". I think it's an "easy once you know how", but not easy beforehand, not easy for everyone, and not every aspect of it is easy even then. Another way of looking at this is that designing and writing and testing and debugging and rewriting and documenting a grammar is always going to be more work than using pre-existing code. For example, although you've put in enough work to be able to use ARON in several projects, it's not ready for others. IMHO it's a non-trivial undertaking. (BTW: does ANTLR 2.x automatically take care of left-recursive grammars?) My experience with parsing is that there be gotchas; this is one reason I'm very impressed with the principles behind XML Schema. (It's a shame it's so soul-destroyingly horrific to actually use. Also XML namespaces: righteous concept, diabolical realization.) The second issue is familiarity/standardization vs. specific-use formats (a kind of DSL), purely in terms of ease-of-use and adoption. I think familiar formats really are easier to read - your eye and brain have internalized short-cuts for interpreting them, so you can quickly work on them. Similar to your finger-memory for your editor. An alternative must be significantly better to overcome this unfair advantage of the incumbent. However, counter-example: for both these reasons (the first is a kind of mechanized version of the second), I thought it would be impossible to displace XML, much as ASCII seemed impossible to displace (there used to be competing character encodings; the present standard, unicode, can be seen as a superset of ASCII). Although JSON seemed wonderfully better (I first saw it in the ActionScript version of ECMAscript), I thought it couldn't overcome XML's incumbency. Yet, JSON is making inroads, and not just in web-clients, but in APIs. It's interesting that JSON lacks analogs to XML Schema, XSLT, XPath; although proposals have been made, they aren't adopted. I wonder if this is because people are now figuring out how to do without these extras? Or if, when they do need them, they just use the XML stack... I think new formats/grammars have the best chance of adoption in niches, when they are so specialized to the task that their benefits far outweigh the advantages of the standardized incumbent - in that particular use-case. For example, most programming languages define their own grammars e.g. python, ruby, java, etc. BTW: in your other comments with code, just indent each line by two spaces for nicer formating. :-)