Hello,

I admit I know very little about URIs and IRIs. I'll try to give the
proposal a more in-depth read, but I have some minor style comments:

1. The light grey is a little difficult for me to read.

2. The function specification is a little confusing to read, because it
looks like the functions are curried, when they are not.

3. Many of the instances of “it is an error” should be replaced with
“assertion violation” (if it's the programmer's fault, for example using
`iri-scheme` on a relative IRI) or “raises an &error exception” (if it's
related to external data). This is the R6RS vocabulary for errors that
raise exceptions and is more specific than R7RS’s “it is an error” which
is undefined behavior.

-- Peter McGoron