[Z3-zemantic] Re: big zemantic storage / some changes

[Michel Pelletier]

On Sun, 2005-05-08 at 14:28 -0300, David Pratt wrote:
> Hi Tarek.  I am going through the Zemantic product, reading the docs 
> and looking at how things are related to each other and trying to put 
> this in the context of a zope2 product. My guess is that you are 
> running the zope2 code with Zope 2.8 installed to get the other 
> relationships to work.

Hi David, sorry about the huge delay in me getting into this thread,
I've been under a lot of pressure lately and I've had to sideline all
Zemantic work, but I've been promised some time coming up in May and
June to get a new version of Zemantic out the door so there will be
progress soon.

With regard to Zemantic running on Zope 2.7, I'm not sure how realistic
that is going to be to happen, although it should work on 2.8 with no
problems.  In addition, I am going to be completely rewriting Zemantic
to upgrade it to rdflib 2.1, which is very different than 2.0 and will
be basically a complete rewrite.  This new rewrite will work with 2.8+.

But getting something running on 2.7 involves a lot of effort for
something I'm not sure provides as much result.  Obviously I don't want
to discourage you from trying, but I feel that time spend working on a
2.7 product only is counter productive, but you may have reasons for it
being very productive, so that's up to you, I can support and assist you
in this area.  I could also be convinced otherwise if there is good
argument.

So far I have heard of two ways that people have considered integrating
Zemantic into Zope 2.7.  THe first is Tres' ZemanticIndex product that
provides a ZCatalog plugin-index backed by rdflib.  I haven't looked at
it much, the second way is an rdflib backend that is driven by the
Archetype reference catalog.  This will basically RDFize Archetype
references for whatever that is worth.

In either case, porting "Zemantic" to Zope 2.7 should be a relatively
trivial exercise.  All the "work" is done by rdflib, really Zemantic is
just skins and security declarations around rdflib.  A catalog plugin
index would involve a bit more trickery and the Archetype wrapper idea
would also involve writing a new backend, also a bit tricky, but a
straightfoward port of Zemantic to be content object (like the ZCatalog)
or a CMF tool would not be very hard.

-Michel

> 
> I don't know how far away 2.8 is from working with 2.7 and the standard 
> type products so I am also trying to decide what to do about upgrading. 
>   My goal would be to have a product that works exclusively for 2.x 
> branch since this is where my all my code is presently.  I have two 
> servers both on 2.7.5 and a development server I could probably put 2.8 
> onto. I have recently gone through the zope3 book and have started to 
> come to grips with the fact that it is a significant departure from my 
> current code.  I am always willing to embrace change but for what I am 
> presently creating it looks like 3 will be out of scope until I really 
> have time to start playing with it and understanding it by doing things 
> as opposed to just reading about differences.  I am probably in a large 
> boat with other people.
> 
> Is this practical or should I just load up 2.8 and then have this blend 
> of 2 and 3 together?
> 
> On Sunday, May 8, 2005, at 08:25 AM, Tarek Ziadé wrote:
> 
> >
> > Zemantic comes with a really nice backend, called by rdflib 
> > (ZODBBackEnd and others in the lib folder). I think you should be able 
> > to code your own backend for postgresql and instanciate the 
> > triplestore with it, so imho I guess there's no need for a 
> > ZemanticExternalRepository.
> >
> > I am very interesting in this, tell me if you start something
> 
> Thanks for the pointers.  I will be attempting this and hoping I can 
> get something started shortly.  I think I will play with rdflib by 
> itself for a couple days first so I can get a feel for it on a stand 
> alone basis.  Can I send Tres's work to you to examine for yourself? He 
> has provided a good starting point.  I am hoping we can get this to 
> integrate with the library by building on what he has started.  The 
> more the merrier if anyone else would be willing to help.  What I could 
> really use is just a data set to work with of some files.  Anyone have 
> a small store of files that I can play with?  What would be good is 
> some sample data for the library example of maybe half a dozen or so 
> files.
> 
> >
> >>
> >> I realize also that 2.8 is around the bend but wonder how large the 
> >> RAM footprint will be to have Zope2, Five and Zope3 together since 
> >> this is the other big issue for me as far as serving since I can't 
> >> afford beefy machines.
> >
> > Zope 3 is not launched through Five, it's just a link to its code so 
> > it is usable within a Zope 2 instance.
> 
> That's good that I understand this, I was afraid you would have two 
> separate Zope instances running that would establish a significant 
> footprint and then add products on top - this would mean much more RAM.
> 
> Regards,
> David
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