auto wrap behaviour when step emits atomic values

[xquery]

Romain Deltour conveyed this idea to me at XML Prague 2015 conference.

When step processing results in an atomic value (or sequence of atomic values) we may want to consider a heuristic for defining some kind of <c:*> wrapping behaviour which is informed by defined or default content-type of p:output port; which avoids throwing an error. We could consider a top level switch that controls this behaviour on the root p:pipeline|p:declare-step.

Its an open question if we need to identify an equivalent approach for other formats ex. a step emitting json could happily emit an array [{},{} ....].

[ndw]

The current spec says that steps produce documents, not atomic values. In XProc 2.0, any kind of document, but still a document. If you wrap 5 in a document node:

document-node { text-node { 5 } }

That should work. If your step emits some sort of binary document for JSON, then that should work too.

[ndw]

Atomic values or lists of atomic values, etc. wrapped in an XDM document node seems to be sufficient.