Re: Some ideas for XML-Query

[Vivien Malerba <malerba gears linuxave net>]

On Mon, Oct 09, 2000 at 09:42:52AM +0200, Gerhard Dieringer wrote:
> Hi Vivien,
> 
> did you already start the new implementation of your Gda_XmlQuery class?
> 
> I would like to discus some suggestions:
> 
> In your old implementation you defined one very large and complex class.
> Why not defining some simple, small and easy to maintain helper classes.
> I suggest to define a helper class for most of the elements in the DTD.
> Of course all binary operators can be represented by one BinOp class, because
> they are all equal with respect to XML-Query, but select, insert, ....
> should all have their own classes, because they have a very different structure.
> All classes should by derived from one abstract base class, that defines some
> virtual methods. These are overridden for the concrete, instantiated classes.
> 

This is a good idea, we need to make classes for things which are common
in all the XmlQuery module. The first test lib I had written was an attemp
at this. However, I would like an XmlQuery class to be easy to use,
specially for changing the type of query:
suppose I have a select query, I would like to have as few work as possible
to create a new one to update some result of the select query. 

So, with your idea, we could make classes for the different type of
queries (select, ...) and create functions to create queries easily
from a query of another type.

What do you think?

> The DTD should be changed, to avoid elements with the structure
> 
> <!ELEMENT parent (child_1, child_2*, child3)>
> 
> by defining special list-tags:
> 
> <!ELEMENT parent (child_1, child_2_list?, child_3)>
> <!ELENENT child_2_list (child_2+)>
> 
> Then all lists can be mapped to a ListCLass. It provides methods, that processes
> all it's children.

I agree with that.

> 
> Please tell me, what you think about these ideas.
> 
> -------
> Gerhard


I haven't found much time lately to work on the queries, and haven't thought
enough about it yet! Also I first want to release a new version of gASQL
working with the latest version of gnome-db (probably next week, and
it would be nice if you could update the german translation :)

Cheers,

Vivien
>