RE: [xml-dev] Web site that emits a continuous stream of XML?

["Toby Considine" <Toby.Considine@gmail.com>]

Changing focus a little:

This sounds like HTTP Long Polling (RFC6202).

It is my understanding that folks are now urged to use WebSocket (RFC6455) (ws:uri)  in preference to HTTP for these types of interactions.


tc
-----Original Message-----
From: Dimitre Novatchev [mailto:dnovatchev@gmail.com] 
Sent: Thursday, May 22, 2014 12:41 AM
To: Costello, Roger L.
Cc: xml-dev@lists.xml.org
Subject: Re: [xml-dev] Web site that emits a continuous stream of XML?

On Wed, May 21, 2014 at 2:30 AM, Costello, Roger L. <costello@mitre.org> wrote:
> Hi Folks,

Hi Roger

>
> I am seeking a web site that has this behavior:
>
> 1. I connect to the web site (I enter its URL) and the web site responds by sending the start tag of the root element.
>
> 2. A short time later (perhaps a few milliseconds) the web site sends the first child element.
>

The definition of "short" isn't precise. If the server sends uninvited, there is no guarantee that the sent data would be processed on time.

> 3. A short time later the web site sends the second child element.
>
> 4. The web site continues to send elements, in a continuous, streaming fashion.
>
> 5. When I disconnect from the web site, it responds by sending the end tag of the root element.

Another issue is that if this server has many (thousands) clients and sends individual stream to each of them, it could easily be overloaded in sending multitude of "offsets" of the same stream. Also, if the stream is produced in real time and is sufficiently long, then it might be impossible for the server to hold all the produced stream data.

I believe that another scenario would be more practical and realistic:
A server sends a single stream and any connecting client starts receiving the stream from the point of establishing the connection.

The only problematic moment here is for the client to recognize the start of some meaningful type (element) and to flush the initial starting sequence.
Of course, for this to be possible, the type of the types whose instances are being transmitted need to have some useful properties -- for example that no type should be the starting part (prefix) of another type -- similar to something I remember from Coding Theory.

There are variations of this requirement -- for example: The client shouldn't need more than X KB of RAM in order to uniquely identify the start of the next type-instance represented in the serialized stream.

Hope this is understandable and makes sense.

Cheers,
Dimitre

On Wed, May 21, 2014 at 2:30 AM, Costello, Roger L. <costello@mitre.org> wrote:
> Hi Folks,
>
> I am seeking a web site that has this behavior:
>
> 1. I connect to the web site (I enter its URL) and the web site responds by sending the start tag of the root element.
>
> 2. A short time later (perhaps a few milliseconds) the web site sends the first child element.
>
> 3. A short time later the web site sends the second child element.
>
> 4. The web site continues to send elements, in a continuous, streaming fashion.
>
> 5. When I disconnect from the web site, it responds by sending the end tag of the root element.
>
> Do you know of any such web site?
>
> /Roger
>
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--
Cheers,
Dimitre Novatchev
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