Re: XML Overlays and Deltas: Existing methods? Ideas?

[Joel Bender <jjb5@cornell.edu>]

>I've had this concept of an XML tree overlay or delta for a while and
>haven't seen much defined so far that I could use.

Too weird!  I've been struggling with the same issue, and just 
decided today that I should post something to the list to see what 
happens.

>There are a number of places this is beneficial for processing, 
>storage, and transmission.

I whole heartedly agree.  My plan is to ship around these changes via 
some reliable multicast protocol.  Fitting the entire change 
description inside a UDP packet would be a major plus.

>This ability should be sufficient to support transactions, transaction
>processing with 'state' being small vs. a large application base,
>backup, logging/auditing, backtracking, 'header compression'-style
>protocol deltas, etc.

Yep.

>This problem is the same regardless of the form of XML, but I am 
>planning to use some solution to this as part of my binary structure 
>XML work.

So the change description is encoded in binary XML?  Or are you 
describing changes to a binary XML document?

>Some ideas to beat up on...

Humm...

><XML ID="ob1">
>   <update xpath="author/book["Bob's Life"]/sold">98</update>
></XML>

The double quotes bother me a little, something might need to be 
escaped, but the basic idea matches my thoughts.

><u:u ID="E9F">98</upd>

Have you thought about insert/append issues?  Are whitespace-only 
text nodes considered significant in your plans?


Joel