Re: [Objectbridge-developers] OJB Homepage, OQL

[Janno K. <ja...@ip...>]

Thomas Mahler wrote:

> Hi all,
>
> In the last days I was working on restructuring the documentation in a
> way that it can be used offline as well as online.
> First visible result: we have a REAL homepage:
> http://objectbridge.sourceforge.net.
> I hope you like the logo!
> I moved the doc directory into src/doc because it needs to be touched by
> the build script (for timestamps etc.) so it's cleaner to have it under
> src.
>
> After setting up a structure for documentation we have now no more
> excuse for not filling the structure with content. So everyone is
> invited to contribute some documents...
>
> During the last week I was having a look at free OQL implementations.
> The Only one I found was from CASTOR (http://castor.exolab.org). I see
> one major problem in reusing their OQL implementaion for OJB: it's so
> tightly integrated into the rest of their system, that it is virtually
> impossible to extract just one or two packages from their source tree...
>
> I found an OQL grammar description for the ANTLR parser generator on the
> ODMG site (http://www.odmg.org, have a look for the file OQL.G in the
> download area). This will help us building an OQL parser. But of course
> all processing of the parse tree has still to be done...
> I'm trying to get a idea what's the best way to go. Any ideas or
> suggestions?
>

Well, one way to make ObjectBridge useable is to implement first 'query by
example'. One db that has implemented it is db4o (http://www.db4o.com). I
believe that also big OODB vendors have implemented similar concepts. I know
that ODMG knows nothing about 'query by example' but it could be later used
to implemend OQL, but for right now we wouldn't need to write OQL parser.
IHMO 'query by example' is also much more usable than OQL or SQL.

query by example looks something like that

PersonQuery pq = new PersonQuery();
pq.setName("John");

Collection col = Db.getInstance().find( pq ); // find all persons with name
John

Even easier way to make OB usable is implement queries similar to EJB's

Janno Kusman


>
> best regards,
>
> Thomas
>
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