[ripe]

> sexps?

Not the person you're responding to, but I think they mean sexps as in S-expressions [1]. These are used in all kinds of programming, and they have been used inside protocols for markup, as in the email protocol IMAP.

[1] https://en.wikipedia.org/wiki/S-expression

[mncharity]

Yes. Not quite a decade before JSON and YAML, what's at hand for a human-readable interchange format for nested data? SGML (no XML yet), something FORTH-ish, make up your own thing, and...? Contemporary WAIS (search as a distinct non-HTTP protocol) shrugged off human-readable, and tried nightmarish binary ASN.1.