Re: Design question - layered approach

[Charles Wilt <charles.wilt@xxxxxxxxx>]

Booth,

It depends :)

The whole point of designing is to determine the answers to those questions.

For a nice intro, check out the April 2009 issue of System i News,
Scott, Paul Tuohy, Tony Cairns, and Don Denoncourt teamed up for a set
of articles which demostraite an RPG business layer with a 5250, PHP,
Groovy/Java, and CGIDEV2 front end.
http://systeminetwork.com/article/rpg-and-web-technologies-get-there
http://systeminetwork.com/article/rpg-web-cgidev2-way
http://systeminetwork.com/article/rpg-web-php-way
http://systeminetwork.com/article/rpg-web-java-or-groovy-way

Also check out:
http://systeminetwork.com/article/writing-reusable-service-programs

HTH,
Charles


On Tue, Sep 8, 2009 at 11:33 AM, Booth Martin<booth@xxxxxxxxxxxx> wrote:
> This seemed simple enough on the face of it, and then of course it
> slipped away.
>
> A case has been made for dividing the pieces of an application into, as
> I understand it, at least three layers.
>
> The first layer is the data and it's constraints and security.
> The second is the layer for business rules.
> The third is the top layer, for the user interface, allowing several
> different UI solutions to co-exist  at the same time.
>
> That all makes sense to me.
>
> Two problems are confusing me.  The second one is: what mechanism does
> one use to arrange the data for the mating of the UI layer to the
> business rules layer?    The business rules program, as I understand the
> design, has to not know or care whether the user interface is RPG, Java,
> or whatever.  What, specifically, does the business rules program expect
> to get & send from & to the UI?
>
> Here's a simple example:  A data file with 2 key fields and a 480-char
> data field.  The UI needs to display the key fields and also a single
> record.  Add/update/delete are possible when the single record is displayed.
>
> (Maybe this is all too simple for layering, but I sooner expect that I
> don't really understand the process itself.)
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