Re: [xml-dev] funny parser

["Steven J. DeRose" <sderose@acm.org>]

At 15:52 +0200 2005-10-10, Dirk Huenniger wrote:
>Hello,
>I just implemented an XML based protocol of interactive device control.
>I am still rather new to XML.
>I am looking for a funny parser that would speed up development of such
>a system significantly.
>
>The Problem:
>A certain part of reality is modelled as an XML file. It has got a size
>of about 100KB and is stored in the RAM of a server. The Server is
>connected to reality and whenever reality changes it changes the XML
>file accordingly. Clients want to know about reality and thus download
>the XML file from the server.
>To keep informed they have to poll rather often and this takes a lot of
>bandwidth and this is not good.
>But usually reality does not change quickly and only a 1KB/minute
>actually changes in the XML file. So what about the server sending parts
>of the XML file. Only the ones that just changed. This way the Clients
>don't have to poll anymore, and we get rid of the bandwidth problem. Of
>course the Clients still have to load the file at the beginning but this
>is only done once.

How about putting an ID on every changeable node, and then sending 
something like:

<replace target='someID'>
   ...new XML for that node...
</replace>

Then the receiving program finds the node by ID, and swaps in the new stuff.

Or, you could avoid the IDs by using XPointer child sequences to 
identify nodes.

Can you be certain that all change requests will be received, and in 
the order they were sent? If not, the problem gets much messier; but 
probably you can ensure that somehow.

S
-- 

Steve DeRose -- http://www.derose.net
Chair, Bible Technologies Group -- http://www.bibletechnologies.net
Email: sderose@acm.org  or  steve@derose.net