PROPOSAL: Re: Automatic Page Updates
Thu, 12 Jan 1995 18:50:40 +0100

Bill Allocca <> writes:
>Is there any way in HTTP for a Server to automatically update a page
>without requiring the user of the client to click on anything?
>The basic answer so far is that the Expires Object Header field (see section
>7.7 of the HTTP/1.0 document) could potentially be used for this purpose,
>but that any client which supports the Expires header field would probably
>only update the page when the user clicked on the "forward" or "back" button
>on a browser.

Because of the other problems that you noted (namely, that clients are not
required to automatically reload a document when it passes the Expired time-
in fact, it would be detrimental to do so), I would propose an
"Expires-Auto-Update:" field - with a value of "yes" or "no", default "no"
in case of the header line not appearing - which would force the client to
automatically update the page. If this header line appears and has a value
of "yes", the client would be responsible for updating the data when it
expires, assuming the document is still being displayed. This would not
break current implementations (excepting that they would not support auto
refresh, but I don't see a way for them to do it anyway), but would allow
a server to tell a client, "here's a document. Update it when it expires."

>Finally, the support for automatic refresh could not really be completely
>Server-driven. As Mark J. Cox points out "since HTTP follows a single
>Request/Responce paradigm it can not be made a function of the Server
>(actually it could, but it would also require client modifications and
>would be far more complex)."

Yup. Because of the stateless (on the server side, at least) paradigm of
HTTP, the client would have to be responsible for automatically refreshing
the data.

-Chris Wilson

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