XML: PDA device --> BigMagicBox --> AS400 native database file (& v.v.)

Esteemed listers,

This is one of those "where ever do I get started" kind of question.  A
search on XML turned up 2872 matches in the archives, but I was only able to
review about 100 of them before my mind turned to jello.

We are investigating handheld wireless devices that will be used by our
field reps.  The devices will be used basically for form entry to replace
paper forms that are now used.

One vendor we are investigating utilizes XML on the device to define the
forms.  There is middleware (MW) in the form of a W2K server that
communicates to the devices and to the AS/400.  It is my understanding that
the MW acts as the communications and translation "host".  The PDA transmits
XML to the MW, the MW receives it, translates it to "something that the
AS/400 can understand", i.e., CSV, or SQL table, then transmits it to the
AS/400.

I've seen what XML looks like and how it compares (or doesn't) to HTML, but
don't really understand how I can harness (?) it on the AS/400.  I scan for
XML at InfoCenter and get 814 hits, so I imagine that there's a lot of
possibilities.  I guess I'm wondering just how much I need the MW for
translating.  Is there a XML-to/from-NativeDB/400 conversion tool in the
operating system?

FWIW, we are not coding Java.

How's that for a start?