Swarm protocol grammar
The Swarm protocol evolved since 2012 in more or less the same direction, gradually becoming richer and richer. Things became a bit hairy last November (2016) once object metadata structure was unified and made part of the protocol. This weekend (11 Feb 2017) I finally realized how to write production rules in a concise way (see index.js). As a result, 20 rather simple rules described the entire syntax.
By the Chomsky–Schützenberger hierarchy, Swarm is a regular language. Hence, it is parsed by regular expressions this package exports.
const re_e = require('swarm-grammar').parsers.EVENT;
console.log(re_e.test('#object+author.json@sometime+origin:field="value"'));
// true