[fpc-devel] TClientDataset (was: Dnamic packages support)

[Michael Van Canneyt]

On Mon, 5 Nov 2007, Graeme Geldenhuys wrote:

> On 05/11/2007, Michael Van Canneyt <michael at freepascal.org> wrote:
> > > There is open source midas.dll implementation called HyperBase.
> > > http://www.vglib.com/link-4.html
> > >
> > > It can be made compilable by FPC to different platforms...
> >
> > Yes, I have it since a very long time :-) But it contains bugs :/
> > But if there is no alternative then that would be an option.
> 
> I  don't understand the internals of Midas, but did help maintain a
> product that used 3-tier (with midas application server).  Could one
> implement a application server using SOAP instead?  

Yes. Such a server comes even standard with Delphi.

> I remember reading
> an article (I think his name was Brian Long or Dr.Bob) where he
> created a standalone (very simple) webserver application using Indy's
> server components and used that as the application server.  Then
> connected with application clients via SOAP+HTTP.
> 
> Is something like this possible with FPC?  I guess the first question
> is, do we have a webserver component for FPC? Secondly, does FPC
> support SOAP?

Yes on both accounts.

> What actually happens inside the midas.dll?

It maintains an in-memory data packet, and is able to do
- local filtering
- local indexing
- locating data
- Maintained aggregates 
- Save/load from file
- Create and merge deltas.

TClientDataset is just a wrapper around this. TBufDataset in FPC has
already many of these things, but not yet all.

Michael.