EQ and join

[Chip Morningstar]

Ping sez:
>It occurred to me while driving to the dentist today that it
>might be possible to retain the flexibility that Dean described
>while still making it easy to do "join" in E.  Could the "join"
>function simply implement Dean's rendezvous-with-a-sealed-box
>protocol, hiding the tedium from the casual E user?

Perhaps something went whizzing by while I was looking in the other
direction, but what is this protocol of Dean's that y'all are talking
about?  Dean is *such* a source of interesting protocols... :-)