Years ago, I was on the editorial board for versions 1.1 and 1.2 an informal standard called SRU. It defined a way to do IR queries over HTTP with XML payloads: you’d send a URL like http://example.com/dbname?someBoringStuff&query=fish, and it would send back an XML document describing the search result — hit count, that kind of thing — and containing payload records.
Since the payload records themselves were also in XML, it was often convenient to just embed them right in the response, where they could be extracted by XSLT or similar. Continue reading