Parsing is of course much harder than writing. I got the psych teminology wrong: per <https://www.ibm.com/developerworks/library/x-namcar/>, Joe English's definitions are:

In a borderline document (presumably a reference to Borderline Personality Disorder), more than one prefix maps to one namespace.

In a neurotic document, the same prefix is used for more than one namespace.

In a psychotic document, two different prefixes are declared for the same namespace in the same scope:

On Mon, Sep 9, 2019 at 9:31 AM Lassi Kortela <xxxxxx@lassi.io> wrote:

>> Thanks for the specifics. Is there a proposal to have SXML built into
>> R7RS-large?

> I'm not sure what that would mean; SRFIs normally describe procedures
> and syntax, not formats, except as an ancillary. The MVP would be a
> procedure that wrote core SXML to an output port as XML, I think.

I thought there'd be read/write procedures and possibly a few map/filter
type functions. A basic SXML->XML writer is less than 150 lines of
Scheme:
<https://github.com/srfi-explorations/srfi-from-asciidoc/blob/master/chibi/sxml.scm>