OPEN keywords

[David L. Andre <DLA at MIT-AI>]

The current situation, in which file systems barf at keywords that they
don't know how to handle, seems more reasonable to me than having them
be ignored.  However, before a special thing is done for OPEN, may I
suggest that there are many places in message passing where a single
message comes in more than one "mode".  A rather limited analogy is in
the window system, where :READ/SET-CURSORPOS comes in :CHARACTERS and
:PIXEL modes.  Not all :READ/SET-CURSORPOS messages might come in both
modes, however, and it might be worthwhile to come up with a general way
of determining whether a mode is supported.  One can also imagine a
"tree" message passing structure, where modes have submodes, etc.

Barring that, both RMS's suggestion of :OPEN-KEYWORD-HANDLED-P and
Moon's suggestion of a global list of ignorable open keywords are OK
with me.