Hi, Fernando.
It does sound like both JEQL and GDMS are exploring similar sorts of
territory. But seems like their focus is a bit different - so maybe
they really can be complementary. I've looked a bit at GDMS - when I
have some time it would be interesting to dig a bit deeper.
BTW, at the moment JEQL supports basic Java scalar datatypes, but it
would be easy to add more (such as binary). The intention is to support
multiway joins in a single statement. At the moment only a single JOIN
is supported - but n-way joins can be implemented by cascading select
statements.
Of course, there's lots of work that could be do with query
optimization, indexing, etc. To what extent are you planning to support
these more sophisticated query processing concepts?
Fernando Gonzalez wrote:
bonjour Michaël, Hi Martin, list:
Yes, indeed we are moving in the same direction as JEQL. However I
think our approach is somewhat more complex and that both projects are
complementary.
Currently we have a library called GDMS that provides access to
different types of sources: shapfile, csv, postgis, ... though a
unique interface. On top of that we are building a SQL processor that
will let us join a shapefile with a postgis table or csv for example.
If I'm not wrong, GDMS SQL processor will have more capabilities than
the one in JEQL because it will have more data types (binary, data,
time, ...) and it has the possibility to include several tables in the
'from' clause. This will let the user to join a shapefile with a
remote postgis table, or define a view (query) involving several
sources that will be updated when any of the involved sources changes.
We plan to provide ability to build scripts but only SQL, nothing to
do with assignments or conditional expressions. This is why I think
both projects are complementary.
If you are interested in any kind of collaboration don't hesitate to
contact me or any member of the team. I extend the mail of Michaël by
providing two links to documentation in GDMS that will help you to
have a better idea of our work:
- user guide:
http://geosysin.iict.ch/irstv-trac/browser/documentation/gdms/developer/manual/gdms_devs_document.pdf?format=raw
<http://geosysin.iict.ch/irstv-trac/browser/documentation/gdms/developer/manual/gdms_devs_document.pdf?format=raw>
- examples of code:
http://geosysin.iict.ch/irstv-trac/browser/documentation/gdms/developer/code/DocumentationExamples.java.html?format=raw
<http://geosysin.iict.ch/irstv-trac/browser/documentation/gdms/developer/code/DocumentationExamples.java.html?format=raw>
long live to JEQL!
Fernando
On Jan 24, 2008 12:15 AM, Michaël Michaud <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
Hi,
Really an interesting discussion.
I will definely keep an eye on this new project.
The feature request from Tore (about querying a shapefile) looks like
one of the interesting features of the GDMS library, the engine
behind
OrbisGIS, a recent project driven by Erwan Bocher.
http://orbisgis.cerma.archi.fr/?page_id=44
Michaël
Martin Davis a écrit :
> Not at the moment, but that's an excellent idea!
> I've thought about it once or twice myself, but haven't had the time
> to pursue it. It would be fairly easy to do this in a
simplistic way,
> I think. Adding the ability to make use of a shapefile spatial
> index would be a bit more work, simply because JEQL doesn't yet have
> the ability to query through an index. That's definitely in the
> plans, however.
>
> So you'd provide the pathname of the shapefile via the
connection URL
> in some way (is there an existing pattern for this?), and then
be able
> to run SQL queries directly against the shapefile.
> This would also work with any other datasources which JEQL offers.
>
> Hmmm - I guess I better start a JEQL listserv!
>
> Tore Halset wrote:
>
>> On Jan 23, 2008, at 19:02, Martin Davis wrote:
>>
>>> A further note: although not currently implemented, JEQL will
>>> provide the ability to directly access tables and queries from
>>> databases. Since there is no "impedance mismatch" between the
JEQL
>>> data model and the DB data, this should make for very seamless
>>> integration.
>>
>>
>> Does JEQL contain a jdbc driver, so that it can be used from a
>> generic java database client to conntect to things like a shape
file?
>>
>> Regards,
>> - Tore.
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>>
>
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