Non-SQL Persistence for PL

Hi, I sent the below message using the wrong mail address.
I hope, it doesn't show up twice in the list.:

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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