See Twisted Matrix Laboratories
> E, Smalltalk, and Scheme proved particularly influential. In E's,
there is a
> sharp distinction between objects which are synchronously accessible
> which are asynchronously accessible. The original use for Deferreds
> represent results from Perspective Broker method calls. E was interesting
> that the entire execution environment had assumptions about networking
> in. E's "eventually" operator [stiegler]
is what originally inspired the
> distinction between "a method which returns X" and "a
method which returns a
> Deferred that fires X".
According to <http://www.zoteca.com/information/wp/twistedusenix.pdf>
the Twisted Perspective Broker...
> uses the simple, flexible and robust capability security model,
> the E language