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Anyone doing 3-tier (n-tier) Client Server???

Can anyone give me some pointers on doing 3-tier (n-tier) client
server with Delphi 2?

Specifically I'm interested in how you connect the client tier to the
application server (middle) tier.  Also what is involved in creating
an applications server to support multiple users without needing
multiple instances of the server application running in the middle
tier?

If its not easy to implement such an arrangement under Delphi 2 will
Delphi 97 (when it's available) make this any easier?

Any input welcomed.

thanks

Phillip B.
phill...@inca.co.nz

 

Re:Anyone doing 3-tier (n-tier) Client Server???


I've played around with OLEnterprise. It allows remote OLE automation. Borland
was supposed to be purchasing the parent company (Open Enterprise). There used
to be a test version on the web.

On 12/26/96 11:30PM, in message <c1b7cc$111ce.198@HERMES>, Phillip A. Baird

Quote
<phill...@inca.co.nz> wrote:
> Can anyone give me some pointers on doing 3-tier (n-tier) client
> server with Delphi 2?

> Specifically I'm interested in how you connect the client tier to the
> application server (middle) tier.  Also what is involved in creating
> an applications server to support multiple users without needing
> multiple instances of the server application running in the middle
> tier?

> If its not easy to implement such an arrangement under Delphi 2 will
> Delphi 97 (when it's available) make this any easier?

> Any input welcomed.

> thanks

> Phillip B.
> phill...@inca.co.nz

Re:Anyone doing 3-tier (n-tier) Client Server???


Quote
Phillip A. Baird wrote:

> Can anyone give me some pointers on doing 3-tier (n-tier) client
> server with Delphi 2?

> Specifically I'm interested in how you connect the client tier to the
> application server (middle) tier.  Also what is involved in creating
> an applications server to support multiple users without needing
> multiple instances of the server application running in the middle
> tier?

> If its not easy to implement such an arrangement under Delphi 2 will
> Delphi 97 (when it's available) make this any easier?

> Any input welcomed.

> thanks

> Phillip B.
> phill...@inca.co.nz

Phillip,

I've done quite a bit of Client/Server type of programming, but I must
confess, I don't understand your terminology, could you please explain?

--Glenn

Re:Anyone doing 3-tier (n-tier) Client Server???


Quote
In article <32C847DD.2...@netmanage.com>, g.ander...@netmanage.com wrote:
> Phillip A. Baird wrote:

> > Can anyone give me some pointers on doing 3-tier (n-tier) client
> > server with Delphi 2?
> I've done quite a bit of Client/Server type of programming, but I must
> confess, I don't understand your terminology, could you please explain?

> --Glenn

Three-tier client/server programming is typically used to avoid the problem
of implementing 'business rules' in a client-side application, then running
into horrible upgrade-management problems when the rules change.  (eg, if
you have a limit of 50% on allowable price changes in an accounting package,
and you have to change the limit).

Some systems implement business rules via triggers and stored procedures in
the database system, but this can sometimes lead to performance problems.

In three-tier systems, what you end up with is a database server,
an application 'sub-server', and a 'thin' client that is nothing more than
a form-based terminal with limited local validation.  When the purchasing
rules change, you update *1* copy of the application server, and all the
clients stay the same.  Clients change only when the transaction structure
changes (eg, when new fields are added).

As far as how they are implemented, that depends a great deal on what toolset
you use to develop them.  I haven't done any of this yet, but you typically
have a 'middleware' provider that sells you the tools to write both the
client and appserver pieces.

If I was writing one of these from scratch, I'd probably look into acquiring
a CORBA-based system of some kind.  If the budget wasn't there, I'd grab the
sources to XDR/RPC from Sun (I *think* they're still available), and use that
to get a feel for the techniques you need.

Exactly how unpleasant that would be depends on the architecture of the
application server you're going to be using.  Even with the friendliest
systems, though, building will be vastly more work than buying, and might
cost more in programmer time and longer delay in delivery than buying a
toolkit.

I could go into more detail here, if anyone's interested, but I think I'll
stop now.  Further comments from anyone who's delivered a three-tier system
would be helpful.

--
Glenn Chambers
gcham...@mail.bright.net
Toledo, OH

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