Re: [Tm4j-developers] what backend to choose

[Kal A. <ka...@te...>]

Hi Stefan,

On Wed, 2003-11-19 at 15:18, Stefan Lischke wrote:
> Hi there,
> 
> I'm wondering which Backend i should use with tm4j. I'm building a XTM 
> ContentManagement System ontop of TMAPI. I want to support a wide range 
> of TMAPI implementations, also TM4j.
> 
> But which backend should i use, the ozone or the hibernate?
> 
> Performance is a big issue. I'm building a lot of XTM Fragments and 
> there is a frequently updating from different Clients (maybe at the same 
> time). My System is running as a Webapplication in tomcat or jetty.
> Which backend supports indexing?
> 

Both backends support the TM4J indexing interfaces. However, on the
Ozone backend, this is implemented using serialized Java HashMaps which
means that a lookup can become inefficient as the topic map gets larger.
At some point in the future I plan to move the Ozone indexing over to
use Ozone's native collection implementations (which should be more
efficient for large collections). On the Hibernate backend, the indexing
interfaces are implemented using Hibernate Query Language (which gets
translated into SQL) - this makes them quite efficient, even as the size
of the database grows.

In my experience so far I have found Ozone to be faster for small/medium
sized topic maps (say up to 50000 topics+associations) but performance
drops off really rapidly as those index HashMaps get bigger (because
they have to be completely read into JVM memory).

Right now my advice would be to go for the Hibernate backend - assuming
that you have an RDBMS you can use.

> Another question is about TMAPI in tm4j, there was a discussion about 
> ID's on tmapi-discuss ML the last weeks and the result was the new Methods:
> 
> TopicMapObject.getID()
> TopicMap.getObjectByID()
> 
> how difficult will be an implementation of these methods? Can i help
> 

That should be really easy to add. The TM4J interfaces already have both
of these methods, so it is just a question of putting a wrapper around
it.

I still need to get those suggested TMAPI changes written up and
circulated to the TMAPI list. I also still need to write up the TMAPI
indexing interface proposal. I'll try and do that today or tomorrow...I
promise! ;-)

Cheers,

Kal
-- 
Kal Ahmed, Techquila
Standards-based Information Management
e: ka...@te...
w: www.techquila.com
p: +44 7968 529531