On Wed, 26 May 1999, Julien Thomas wrote:
> What are the other major benefits of 3-tier client server compared to
> 2-tier? if any?
Deployment is trivial, logic is seperated better, you can use OO design,
it scales (C/S does not, well, not very well)
> Does MIDAS simplify or complicate the development?
For me - tho I _am_ an Inpirse employee, but most people here know I say
what I think - 3-tier in general simplifies development, and adds a lot of
other benafits.
The project I'm currently working on it a 4-tier, I suppose, web-based app
- using JSP, Java, beans, corba and interbase. I'm finding writing using
CORBA -
which is a bit more manual than using MIDAS which does a lot of it for you
- to be excellent - I can abstract stuff out into objects, and keep all my
state and stuff in the server, not on the client. I can also write clients
in whatever language I choose - so far, its java to java, but in the near
future, I plan to use Delphi to add in both CORBA servers and clients, for
various things that are 1) internal and 2) not suited to the web-based
medium. The flexability is excellent.
>
> The Borland blurb on MIDAS talks about putting business logic into the
> middle tier server - this is a bit vague. What exactly do they mean by the
> 'business logic'? How much can you take out of the client?
>
OK, the ideal situation is not always atainable, but its something like:
Client - displays stuff, handles data entry, maybe basic validation (did
the (l)user enter a letter into an number field?), but mostly
presentation.
the application server handles validation, enforcing of rules (was that
pay raise less than 50%? Was the employee name "nwise", if so add $100K to
the salary etc). With MIDAS it also handles what needs to be sent down
to the client, what to post back to the DB when it comes back, etc.
If you change a rule, you roll it out on to "N"
application servers, NOT on to the client, 'cos the client doesn't care!
All it cares about is "was that valid or not?,, and if not, why?"
Obviously, some changes need a new client, but not most of them.
3 tier if also excellent when you have 2 seperate DB's - eg Oracle and
Informix - being hit by the same app. It much easier than trying to
handle 2-phase commit manually :)
then there is the dB server (Oracle, interbase, MSSQL, whatever) which the
client never hits (so no installing libs on the clients - dont under
estimate the cost of this), and the middle
tier can handle connection pooling, etc. I can run a fairly large web site
on about 20 connections - most of the time, people are looking at info,
not posting it back or requesting it.
Another advantage, which is fairly specific to MIDAS, is if you need 10
records to display a grid, you can tell it to only send 10 (or 15, so you
have the next 5 to show the user), which rocks for WAN apps.
> So really what I want to know is should we use MIDAS as part of our
> redevelopment of our Delphi application to access our SQL 7 server?
>
What does the app do? How many users are there, and where are they
located? Do they have full-time connectivity to the server, or only part
time?
> We will be using two remote mirrored servers as well.... with a possible
> requirement of remote access in the field and possibly further?
Sound like MIDAS, and client-data-sets, would be rather usefull for you.
I know its a bit of a cop-out, but get hold of Richard Vowles from Inprise
(09-3600231) - he can make a fairly good estimation of whether or not
MIDAS is the right thing for you.
Nic.
Nic Wise - [EMAIL PROTECTED] - http://users.iconz.co.nz/wiz
also: [EMAIL PROTECTED], [EMAIL PROTECTED]
Pascal-a-holic, Underwater Hockey player, and X-Phile.
(not sent from home)
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