RE: Separation of Presentation, BL, and I/O Tiers -- RPG400-L

I have some of the same questions, so I will be interested in the responses.


Regarding the first question, my only input is that if it is an existing
database with programs already using it, forget constraints.  It's almost
impossible to reengineer a system.  If it is a new database and you have
control over the program design, they are wonderful tools, but almost
require matching triggers to prescreen for the same errors that the
constraint will encounter.  This is so you can offer a "soft" failure of
some sort, rather than the hard crash that results from a constraint
violation.

On #2, It depends.  :-)    On #3, I'm not sure what you mean by "data
transport".

I have been successful at moving my I/O into service program routines, but
being generic, they contain no business logic.  It probably would not be too
hard to have the I/O modules themselves call specific business logic
routines, based on the file data being requested, but I haven't tried to
implement that yet.  Again, this would probably only be practical on new
designs.

My biggest interest is how people are separating their presentations from
the business logic.  Are the business rules kept in some sort of
maintainable table?  And how are screen entry fields validated against the
table in a manner that could be generic?

> -----Original Message-----
> From: MWalter@hanoverwire.com [SMTP:MWalter@hanoverwire.com]
> Sent: Wednesday, April 10, 2002 11:07 AM
> To:   rpg400-l@midrange.com
> Subject:      Separation of Presentation, BL, and I/O Tiers
>
> Hello all,
>
> I am trying to define what would be required to separate our presentation
> from business logic, from database I/O and would like your opinion on some
> issues. Any input would be greatly appreciated.
>
> 1) How do you feel about physical file constraints to provide some field
> validation?
> 2) Does field validation belong in the database tier or the business logic
> tier?
> 3) What is the most advantageous method of data transport (Data
> Structures,
> Data Queue, Trigger)?
>
> I realize that these questions are quite broad and probably the most
> obvious answer is 'It depends'. But what I'm looking for is options based
> on personal experiences
>
> Thank you very much.
>
> Mark
>
>
> Mark Walter
> Sr. Programmer/Analyst
> Hanover Wire Cloth a div of CCX, Inc.
> mwalter@hanoverwire.com
> http://www.hanoverwire.com
> 717.637.3795 Ext.3040
>
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