I've seen many parsers, from ad-hoc regexes to real grammars like this one, that attempt to process natural, human-readable query strings that resemble Google searches. (The example at the top of this writeup, `john city:"new york" last_called < "3 days ago"`, illustrates what I'm talking about.) But there's no standard definition that I know of that could make all these slightly-different implementations interoperate.<p>Does anyone know of any specification of a colon-style query syntax that other projects could reuse? Even something semi-formal would be better than nothing.