Merry Christmas!

At 01:35 PM 12/9/97 -0500, you wrote:

-snip-

>One alternative is to take the interactive maintenance program, write it in
>Java and use ODBC to read/update the database.  That can be hairy
>because then the business rules move from the server to the client(s).

I'm probably going to repeat myself here, but here goes. This looks like a
2-tier implementation (and I mean a 'logical' 2-tier design, which can be
implemented on 1 or 2 'physical' platforms).

The alternative I want to posit is a 'logical' 3-tier design, where the
business rules reside on an intermediary tier. As with 2-tier models, a
3-tier model can be implemented on from 1 to 3 'physical' machines.

I believe that many of your concerns can be addressed with this model.
E.g., the client only needs to know how to make requests from this
middleman server. The _middleman_ is the only thing that needs to know
'how' it gets the data from the backend data servers (like SQL Server or
Oracle or DB2/400).

The client (logical) is primarily concerned with the presentation
layer—requesting data (for display) from the middleman, sending input data
to the middleman with a request to write it to the database, etc.

Pieces of the middleman can be (re)written as needed or possible, to take
advantage of database-specific means of communication, if desired. E.g.,
data queues could be used to speak to an AS/400, where some other means
could be used for SQL Server, optimized for that database.

Again, the client need know nothing about the details of how the middleman
talks to the backedn databases. In this way, the portability of the client
is greatly enhanced.

'Nuff said!

-snip-

>>All I am trying to point out is that data queues are not a flaw in Java.

In fact, data queues, in and of themselves, have _nothing_ intrinsically to
do with Java. They are an optional means of communicating with an AS/400,
if a developer wants to do so. The classes of the AS/400 ToolKit for Java
merely use Sockets calls to server apps on an AS/400 to implement the use
of data queues. Any one of us _could_ have done the same thing, did we know
the details of the interface.

Cheers

Vernon Hamberg
Systems Software Programmer
Old Republic National Title Insurance Company
400 Second Avenue South
Minneapolis, MN 55401
(612) 371-1111 x480


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