Why would you get ossification? The point of XML based RPC protocols was that XML had lots of extension features like namespaces and parsers were dime a dozen.

Why would you get ossification? The point of XML based RPC protocols was that XML had lots of extension features like namespaces and parsers were dime a dozen. The forgotten 2000-era web had solutions for all of this in the form of XML and XSLT. The server serves XML, which is "semantic" (data structures). The XML has a header pointing to an XSLT file, which defines a functional transform of the XML to HTML. You could use namespaces to embed semantic info inside other schemas like XHTML if you wanted, also. It never took off, partly because XSLT was a pretty unpleasant programming language (I actually built a product with it back in the day), partly due to latency reasons and partly because the XML vision wasn't sufficiently backwards compatible with regular HTML. These days browsers don't support such tech anymore, so you need to treat HTML+JS as an app platform, HTTP as an RPC protocol and JSON as the serialization format but because that arrangement was never really designed per se there are lots of little missing pieces, like being able to discover the RPC protocol a web app uses without actually executing that app.