Exiv2

The bash shell has "$IFS" "set -v" and others ("noclobber" comes unbiddden to mind).
Python, Perl and even C have such things as "identify," "load" and "include."
So instead of asking Andreas to re-code exiv2.cpp every time one wants to hardwire a new namespace into the library or executable, while at the same time saving the user time in typing out (or if calling on the library routines, making references to several relevant libs in sequence), I think the idea of a "mode" or "state" which can be invoked directly or tangentially has legs.

For instance, what are conspicuous by their seldomness, even in the XMP Iptc Core Extended list of elements, are fields one can use to record comments on an image or other media item beyond what IPTC Caption, EXIF User Comment or Image Description already supply, or much in the way of opportunity to "twin" or "affirm" the data in the above-named in the XMP block of a file. This is particularly true, and may prove to be important, when someone is given temporary or conditional rights to certain media, inherits a library of pictures or other media files for which there is no ownership applicable or pending (sites gone 404 or collected smart-card downloads from one or many cameras), or when someone is not part of a press, media news or other organization but still wants to be able to dazzle their friends and associates with the same level of "brand identity" as the ANPA, Adobe or Microsoft accommodate themselves. Exiv2 in its current state can give them this, of course, but what may discourage folks from making use of that "power" is the amount of time involved in invoking "reg" every time one wants to add a custom tag of this type.

Something to think about (that is, if you can interpret all my cumbersome gibberish and blather). :)

Steve Wright