Re: the meaning of stateless

On Mon, Apr 22, 2013 at 4:18 PM, Mark Baker <[email protected]> wrote:

> On Sun, Apr 21, 2013 at 7:52 PM, Brian Craft <[email protected]>
> wrote:
> > Fielding's definition didn't do much for me, because the terms aren't
> adequately defined,
>
> They are, and the definition is most definitely adequate, trust me on
> that.


I don't agree. Take this statement, for example:

"Each request from client to server must contain all of the information
necessary to understand the request, and cannot take advantage of any
stored context on the server. "

What does "understand" mean in this sentence? I'm not aware of a technical
definition of "understand" as it applies to computer systems, and it's not
defined in the paper. Again, take the "query by POST" pattern. The eventual
GET depends on a previous POST. Does the server "understand" a request that
depends on a previous request? What about "stored context"? One would
reasonably believe that POSTing a query creates stored context on the
server which later requests may take advantage of. But this sentence says
that it must not "take advantage of any stored context on the server." I
assume this apparent contradiction is due to some different use of terms,
that "stored context" doesn't mean what one would reasonably assume it
means, or something. If this is a different usage of the terms, they should
be defined somewhere.

My current guess is that "understand" means that the communications layer
can read the request and generate a valid response, including the case
where the POST goes missing and it must return a 404: that it still
"understands" the request even though the app can't process it since the
depends on a previous request.

But then it gets really odd with claims like "the server doesn’t have to
manage resource usage across requests." How is a POSTed query not a
resource on the server that must be managed across requests? Again, if this
is to make sense then the terms must have something other than their usual
meaning. Is it "manage"? Maybe the server doesn't "manage" the resource
because the client directs the creation of it? But, then, the server will
have to manage the destruction of it, because a server can't allow clients
to create an unbounded number of transient "query" objects and count on the
clients to clean up after themselves. So what does that phrase mean?