Re: "Version" Aversion

[Michael McClary <michael>]

> From tribble Mon Dec 11 20:58:19 1989
> 
> In a Xanadu environment, even though Bobp and Marcs have separate
> front-end machines, they probably share the same server.  Thus they
> could pass the primary "Xanadu Glossary" Bert back and forth.
> 
> I'm not sure cross-machine hopping of Berts is that far away.  We can
> get much of the capability by letting Berts get hopped remotely
> (without migrating them).  The normal double-bert scheme for editing
> let's us edit efficiently.

Ah!  This looks like a solution to the (as far as I know) not yet
addressed problem of how to decide what to make local in a multi-
backend Xanadu network:

Make a local copy of all the data covered by any orgl on which a
grabbed or hopable bert sits, and which isn't on a backend that's
defined to be "instant access" (such as the "backend" that
represents the CD-ROM in the next drive over).  (Actually: schedule
it to be made local in due time, but raise the priority of those
portions to be read to the front end.)

Once the bert is dropped, hopped to another orgl, or hoppable bert
is frozen, the data becomes eligible for eviction (to archive, or
deletion if it is stored on other nearby backends).  It gets more
eligible as time goes on without a bert holding it local.  (Does
that mean it's gotta wait for version 3? B-) )

Bingo.  Multi-backend caching and multi-backend query optimization.

(Do will need some way to decide when to stop following multi-orgl
 stuff, so we suck in structured documents, but don't follow links
 until we've sucked in the docuverse?  There may be a problem with
 foreign data that COULD become local, as in digitized audio or
 video that you only want to pull off the special-purpose hardware
 when you're gonna edit a sound-bite.)

(Might also be nice for a front-end to be able to say "and suck in
 one layer of referenced documents so my user doesn't have to
 twiddle his thumbs."  I suspect this can be done explicity by the
 frontend, by asking for the bert contexts of all the links, and
 then for new berts on those.  But it might be nice to ask for
 that at the backend level, so the remote backend can send a care
 package, rather than waiting for the frontend to find out what
 to ask for.)

	Am I reinventing a wheel?
	michael