Re: XML structure

[Vivien Malerba <malerba linuxbox com>]

On mer, 23 fév 2000, Rodrigo Moya wrote:
> Hi!
> 
> Definitely, the XML structure described by Vivien will be the way to go.
> Here are my comments:
> 
> > * it can be easily extended to non DBMS providers.
> > * it can be easily expanded in the future for some other type of
> sources (LDAP,...)
> Yes! the LDAP server will make use of this for all the commands. The
> struct you described will allow us to send complex queries to the LDAP
> server in one step.
> 
> > * it does not require some changes in the IDL since the query is sent
> as an XML string
> Maybe just adding a execQuery (or sendQuery) to the GDA_Connection
> interface, because I've first thought of creating a new interface
> (Query), but this will mean adding lots of ORBit stuff. What do you
> think? The first solution implies a new method in each server which will
> do the conversion (if needed) from the XML string to SQL or whatever,
> and we could have the full-featured Query object (mainly to follow the
> object-oriented design of the library) in the XML module.

I agree: for the gda-connection, add nothing to the IDL (XML strings sent
instead of SQL queries). 

For the XML module, creating a Query Object is a good idea, but for that Query
object, do you have in mind something different than the XML tree I described
in my proposal? 

> 
> > * its use is not required and clients can still send SQL (or whatever)
> commands
> >  directly
> Yes, just the "specialized" parts will use this (the XML client module
> for retrieving data for the exported objects...). Also, the import part
> 
> > * each server need to implement an engine to recognize the XML string,
> 
> >  convert the XML string to a tree, and that tree to an SQL query which
> 
> >  is quite a lot of work (for all the SQL like servers, the different
> >  emplementations can be easily adapted from one SQL server)
> We should have all this common code implemented once only, as the
> servers contain enough repeated code all over (the ORBit part is always
> the same. As soon as we've got the gda-buildserver script, we should
> modify all the providers to use this common code generator, but this
> needs a deep thought).
> 
> Of course, this XML structure has to fit in the XML files generated by
> the client lib to be able to save, restore ..., so a <QUERY> (is query
> the correct name to use?) tag will be understable by the client lib.
> Also, a new GDA_Connection_FEATURE_XML_QUERIES will be added.
> 

Ok!