RESTful Web services and DAL

[Doug Tody]

On Wed, 14 Mar 2007, Norman Gray wrote:

> > What may not fit into the REST model well is asynchronous messaging.
> > Perhaps this is just a GET where we hold the HTTP connection open and
> > stream messages periodically?
>
> Others have responded to this.  I'll simply add that I think that the
> response to this goes to the heart of the set of REST observations,
> which is that one can usefully see HTTP as an application protocol,
> and not just a transport protocol (others have made this point
> earlier in this thread).
>
> If you do this, then you will be pushed towards an architecture which
> is robust because it goes with the grain of the web rather than
> against it.  Guy's UWS shows how one can approach a problem which
> _appears_ to require an asynchronous messaging solution, and instead
> design an architecture which addresses it using easily passed-around
> names, which is better because it's simpler.

So how would you propose to implement low latency asynchronous messaging
with an HTTP-based protocol where the client cannot expose a port?
A solution which involves polling alone (a synchronous GET) is not
acceptable.  We want to support polling, but asynchronous delivery of
messages (a "push" by the service with no response) is essential in some
distributed computing applications.  I think it could be done fairly
simply as I suggest above; this approach is probably similar to what
AJAX does.

	- Doug