[XeTeX] Use of different input mappings

[Daniel Stender]

Hi folks,

since the use of a custom input mapping (.tec) is possible like:
\newfontinstance\devanagari[Script=Devanagari,%
Mapping=velthuis-sanskrit]{foobar}, what would be the usage
for switching mappings within the same font like:
.... {[Mapping=foo] ...} ... {[Mapping=bar] ...} ... ?

greetings,
Daniel Stender