9.7 Extension
The choosing channel carries no version number. It grows by addition, under these rules.
9.7.1 What may be added #
A member of the request or of the answer. A party MUST ignore a member it does not recognise, so a requester MAY send one and MUST NOT depend on its effect.
A line type from the chooser that the requester may ignore and
still conform: a requester MUST ignore a type it does not recognise
(§9.3), and goes on waiting for the answer.
9.7.2 What may not be added without a version #
A change to the meaning of an existing member or line. A mode beyond
open and save. A second answer, or a line from the requester after
the request.
9.7.3 What may never be added #
A way for the chooser to hand over a file. Nothing on the channel may carry an open file, its contents, or anything but a path from the chooser to the requester. The requester opening what it is pointed at, as the person, is what lets any program use a chooser it does not trust.