Re: diffenrences between providers / servers

[Vivien Malerba <malerba linuxave net>]

On mer, 26 jui 2000, you wrote:
> Hi,
> 
> > > Isnt it possible to write a SQL abstraction layer that provides
> > > one defined SQL dialect and translates them into the data source's
> > > SQL ? 
> > > 
> > That is the very reason we started to create XML queries (and the the other XML
> > stuff), to create a way of describing a query using XML so every DBMS provider
> > will translate the XML queries into its own SQL like language (DBMS providers
> > are part of gnome-db). H
> Ok, why didnt you use a specific SQL set ?

For several reasons:
1) an SQL statement is a string, so the actual structure of the query has to be
built from the string, which is a quite difficult job.
2) we bon't want to have something limited to a common subset of what ALL the
databases are able to do.
3) some DBMS don't use an SQL like language at all, and we want to be able to
support them under GDA (like LDAP).
4) we can extend the queries in many ways we may want with the power of XML.

> What's a DTD ? 

A DTD is a document describing what can and cannot appear in a XML document (it
defines the tags (elements) and their attributes).
Have a look at http://zvon.vscht.cz/ZvonHTML/Zvon/zvonTutorials_en.html where
there are good explanations.

Cheers,

Vivien