Annotations [was Re: Apps Messaging -- A New Approach

[Mike Fitzpatrick]

Hi Mark,

> No.  The task just knows that applications may issue annotations,
> and yes it ought to structure its menus with that in mind.  But in the
> kind of case we're talking about here it has no knowledge, at any 
> stage of the interaction, about what any of these annotations (if there
> are any) mean.  The user selects one of the available options, and
> the sending app blindly passes the annotation along to the recieving 
> app.  Any message parameters, return values etc are treated precisely
> the same at the sending end regardless of which annotation, or whether
> any annotation at all, is selected.

	I think I understand:  Task A posts a message with an annotation
and Task B creates a menu entry, if the user selects that entry then that
message is sent back to Task A as the command?
	As it's being used currently I'll admit it's clever, but how do 
we describe this in the spec?  The problems I see are that

	- tasks must implicitly assume that a base message of a particuar
	  type means it should create a menu entry e.g. only do this for
          the process.table.votable messages
	- messages are assumed to have a fixed format when sent back, e.g.
	  can contain only a single arg which must be a filename to 
	  operate on
	- suppose in IRAF I want to post that I can do 20 things with a
	  votable, does each of them become a menu entry?

In the first case the spec would need to identify 'process.table' as the
special message type and prescribe some sort of behavior an application
should take as well (but only when it sees the annotation?).  Why not just 
use a more explicit 'gui.addMenu' message to instruct the app, the args 
to that message could then be variable and be returned just as they are 
now (we could even have a syntax that says '$F' in the arg string should 
be replaced with the file name).
	Are there use-cases for annotations besides creating menus that
couldn't likewise be handled with a special mtype?

Cheers,
-Mike