Q: Should "file" be made absolute wrt to the current base URI, or left
unchanged (effectively making it relative to the implementations
notion of current working directory)?
I would say the former (make absolute against the current base URI)
since it would be more consistent with how the core XProc steps behave.
For instance, the p:load and p:store steps, or the p:document construct
use the current base URI. (On the other hand, I am well aware of the
problems with getting the current working directory in XProc...)
Just one thought: what about making these steps more generic, and make
the use an "href" option instead of "file"? That would allow
implementations to support also other URI schemes than "file".
For instance, in our implementation we support a whole bunch of URI
schemes, and support for additional URI schemes can be easily providedby
the user/programmer. I can imagine that one may want to use the
fileutils steps to access the classpath, for instance, or even
collections/documents in a native XML database, ... In our
implementation, all you have to do is to pass a different URI scheme to
the XProc steps.