Issues of state

[Steve Holden]

Cameron Laird wrote:
> In article <7xfy2t8l5n.fsf at ruckus.brouhaha.com>,
> Paul Rubin  <http://phr.cx@NOSPAM.invalid> wrote:
>> claird at lairds.us (Cameron Laird) writes:
>>> Others have answered this at other levels.  In elementary terms,
>>> there truly is a difference, Paul, and one that's widely reified:
>>> a "desktop client-server" application typically listens through
>>> one socket, which therefore constitutes an index of the connection
>>> or client, while a Web application communicates through a sequence
>>> of independent HTTP transactions.  The latter can manage state only
>>> to the extent it passes session information around.
>> Is this significant?  In the case of a single user http app running on
>> the same computer as the browser, the server should only listen on
>> 127.0.0.1.  Every http hit then almost certainly comes from the same
>> session.  If there's doubt, the app can always set a random cookie at
>> the initial screen and check that the cookie never changes.
>>
>> If there's only a small amount of session state (say up to a few
>> hundred bytes) you can put it entirely into browser cookies and send
>> it on every single http hit.
> 
> I'm not sure what we're discussing.  Yes, I agree those are 
> mechanisms by which Web applications manage state.  Apparently
> we agree that, in a general Web application, state management,
> or related persistence, requires *some* mechanism or assumption.

As far as I'm concerned the major issue with trying to have "desktop web 
apps" compete with true windowed applications is the difficulty of 
maintaining sensible interactions with the interface. AJAX designs have 
increased the interaction level at the expense of greater complexity - 
there is more state to be transferred, and a much higher interaction 
rate with the server. But the browser is a terrible front-end for AJAX 
designs because it doesn't record the state changes that take place as a 
result of requests for updated InnerHTML content, so if the user is 
unwise enough to press the "back" button she loses all traces of the 
non-page interactions that have taken place since the page was loaded.

So "desktop web apps" should ensure that they get displayed in browser 
windows with minimal user interface decoration. But even then there's 
always that chance that sophisticated users will use keyboard shortcuts 
like ALT-left-arrow.

That, in summary, is why my 2004 PyCon paper[1] was subtitled "The Back 
Button is Not Your Friend".

regards
  Steve

[1]: http://www.python.org/pycon/dc2004/papers/18/Setting_A_Context.pdf
-- 
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