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Re: Looking for a good PDOM

On Mon, 17 Apr 2000, you wrote:
> Hi,
> we are looking for a free persistent DOM implementation.
> We have a DOM which may get very big, and may not fit to 
> memory (RAM) anymore, and which is queried with XPath.
> This PDOM should be implemented in Java, as we want to
> integrate it into our MOM (message oriented middleware)
> (If you are curious: http://www.xmlBlaster.org).
ozone/XML is 100% Java

> The PDOM should cache parts of the DOM tree to/from harddisk
> transparently, so that the XPath/XSLT engine doesn't notice it.
ozone works this way (not only for DOM objects, btw ;)

> Here is our wish list :-)
> - Free for commercials as well (like LGPL or similar)
the ozone public APIs are under LGPL. The DOM code that we are currenly using
is a port of OpenXML which is ok for commercial use too.

> - Allowing to use any XSL engine (we use currently XT from J.Clark
>   to query the DOM with XPath, since it is the fastest engine)
We have tried Lotus and Xalan without problems. It should work also with XT.

> - Should work non validated as well (no dtd, since the DOM is generic).
ozone/XML basically provides the persistent DOM. It can be used with any parser.

> Could ozone be a solution for this?
Yes, I think so. BUT, since ozone/XML is based on the general purpose OODBMS
it is not as fast as deticated XML storage solutions, yet ;) (see the excelon
comparison thread) And the programming must follow ozone programming rules.
This means any DOM query and manipulation should be done on the server for
performance reasons.

Right now I'm working on a client site cache that should cure both problems. I
will post news here. On the other hand, if your XML documents are actually to
big to fit into memory, than a client site cache makes no sense for you in any
case and the server site processing of the current ozone/XML is the best choice
for you.

Falko Braeutigam                         mailto:falko@softwarebuero.de
softwarebuero m&b (SMB)                    http://www.softwarebuero.de