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Re: PDOM implementation



On Wed, 27 Oct 1999, Ann Tecklenburg wrote:
> http://xml.darmstadt.gmd.de/xql/apidoc/index.html
> 
> http://xml.darmstadt.gmd.de/xql/xql-examples.html#PDOM
> 
> There is really alot of detail about how they implemented their
> PDOM in the last reference although no source code.
> 
> I think  their implementation represents an educated and
> fairly efficient approach.  We will have to do much the same
> in Ozone to ever get decent performance.
IPSIs PDOM is lightning fast compared against what we we can do today. But the
goals and strategies behind seem to be very different from our MDOM so I don't
know, if we can re-use that much of their "knowledge".

I see two ways to implement a persistent DOM:
1) the DOM classes know how to deal with persistence (IPSI PDOM)
2) the DOM nodes are stored in a database (ozoneXML MDOM)

The PDOM solution is fast because all the DOM-specific information can be used
to optimize the storage (the DOM code itself includes the storage code) and it
does not need any server. But this is also the problem, as far as I see, it
is impossible to build a transaction save system with PDOM. (a feature that
is a must for a document server for example) And if they start to use a database
as storage backend to come around this problem, they will lose the performance
advantages.

In the future we will try to re-work especially the cluster management of ozone
to better meet the needs of DOM. The performance of ozoneXML must be
comparable to PDOM. However, it will never be as efficient as such an
specialized system. 


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