Re: Non-SQL Persistence for PL

I for one disagree Hans.
This kind of discussion is the sole reason I even read this mailing list.
and a little extra technical details that I can (optionally) ignore is
far better
than spam about all kinds of things.

David Whitten
[email protected]
713-870-3834

On 8/31/07, Hans Chalupsky <[email protected]> wrote:
> Kamiz,
>
> we should probably take this off-line from the forum, since it is
> getting too much into internal details.  The persistence scheme uses a
> few tables for different objects such as constants, definitions,
> propositions, etc., but it is similar to a "one generic table" approach
> as used, for example, by Jena.  That has some performance implications
> that we still want to address down the road, but haven't yet.  The
> system for loading objects dynamically is quite hairy, so I don't
> advise you do try to mess with that.  Anyway, we can continue this
> conversation in private email if you want.
>
> Hans
>
> >>>>> darabi  <[email protected]> writes:
>
> > Hi,
> > if there is a way of efficiently serialising and deserialising
> > only those objects which represent definitions and propositions
> > as you do it with your 'schema-less' RDBMS, that would surely
> > be a better approach than serialising the complete object graph.
>
> > When you say you use the RDBMS to store serialised objects in it,
> > does that mean that you have one single table with rows for each
> > proposition or definition? Or different tables for different
> > types of objects? And if I understand correctly, the caching/
> > paging is implemented in Stella on top of the RDBMS?
>
> > I would like to try either AllegroCache and/or other object
> > persistence tools, so I looked into the code of the rdbms
> > system and saw how you use demons and db-relation-goes-xxx
> > functions and have a vague idea of what would be necessary.
>
> > The experimental code you mention, would be very interesting
> > as the rdbms code is still very close to the notion of
> > tables (deftable ...). I would appreciate even small code
> > snippets or other information about the mechanism you use
> > to store propositions in a generic way.
>
>
> > Thank you.
>
>
> > Kambiz
>
> > ----- Original Message -----
> > From: "Hans Chalupsky" <[email protected]>
> > To: [email protected]
> > Cc: "PowerLoom Forum" <[email protected]>
> > Sent: Donnerstag, 30. August 2007 0.00 Uhr (GMT+0100) Europe/Berlin
> > Subject: [PowerLoom Forum] Non-SQL Persistence for PL
>
> > Kambiz,
>
> > we do have an experimental version of persistence that doesn't require
> > you to have a DB schema, but that basically persists PowerLoom
> > definitions and propositions in a special-purpose "schema-less" RDBMS
> > database.  The system then pages those objects in on demand and uses
> > extensive caching to make things fast.  In a sense this is
> > implementing a type of persistent object system by serializing the
> > objects to an RDBMS.  The problem with this is that it isn't quite
> > complete.  We've loaded, persisted and queried large ontologies with
> > that, but there are a variety of loose ends that would make this
> > difficult for you to use at this point.
>
> > Several years ago we've played with some persistent object systems
> > (such as Versant and PLOB - a free version of persistent Lisp
> > objects), but the performance was never very satisfying.  That might
> > have changed by now with Allegro Cache, but I don't have any real data
> > on that.  The other issue is that a loaded PowerLoom module has a host
> > of PowerLoom and STELLA data structures associated with it that all
> > would need to be persisted, which means that you basically have to
> > make all object classes of STELLA and PowerLoom persistent to make things
> > work (without some major re-architecting).  I don't know how difficult
> > that would be with Allegro Cache, and I'd be interested to hear some
> > experiences from you if you venture to go that route.
>
> > Hans
>
> >>>>> darabi  <[email protected]> writes:
>
> >> Hi, I sent the below message using the wrong mail address.
> >> I hope, it doesn't show up twice in the list.:
>
> >> ----
>
> >> Hello,
>
> >> I have a need for persistent knowledge bases and thus
> >> have been experimenting with the rdbms (and sdbc) system
> >> which you kindly released some time ago.
>
> >> My (maybe short-sighted) conclusion is that rdbms is very
> >> well suited for accessing large amount of data which
> >> is already stored in an SQL DB and for making that data
> >> available to PL's reasoning mechanisms.
>
> >> But, if one has no existing SQL data and wants to persist
> >> a KB of concepts and relations which are subject to frequent
> >> change, then the limitations of the DB in terms of 'high
> >> cost' of schema evolution also limit the possibilities
> >> of rdbms/sdbc.
>
> >> Have you or others taken another path: to use object level
> >> persistence as provided by Franz' AllegroCache or other
> >> 'object databases' to store the relevant parts of the
> >> knowledge base?
>
> >> Of course, this would only work in the lisp version of PL,
> >> so it might be out of scope. OTOH, there is also db4o for
> >> Java and C++, so maybe it wouldn't be impossible to implement
> >> it in a cross-platform way.
>
> >> But, I would be interested in any thoughts you might have
> >> on this topic. Would it be possible to use the CLOS version
> >> and identify some classes (e.g. named-description,
> >> native-relation, context, module) which make up a PL module,
> >> and persist them to an object database?
>
> >> If yes, could you give me some hints as where to look into
> >> the code?
>
> >> Thank you very much.
>
>
> >> Kambiz
>
>
>
> >> _______________________________________________
> >> powerloom-forum mailing list
> >> [email protected]
> >> http://mailman.isi.edu/mailman/listinfo/powerloom-forum
>
> > _______________________________________________
> > powerloom-forum mailing list
> > [email protected]
> > http://mailman.isi.edu/mailman/listinfo/powerloom-forum
> _______________________________________________
> powerloom-forum mailing list
> [email protected]
> http://mailman.isi.edu/mailman/listinfo/powerloom-forum
>