RE: A design philosophy question

["Joe Pluta" <joepluta@xxxxxxxxxxxxxxxxx>]

> From: Booth Martin
>
> Well given that the BL programs are already in place Joe then the
> answer is
> quite simple.

It's never this simplistic, Booth, except for trivial programs.


> One program with the screens designed within it.  No work is being done at
> the green screen level except to populate a few data structures.

I don't think so.  The business logic (grabbing some related data,
performing some calculation, updating some files) is quite different from
the presentation logic.  The presentation logic may invoke five different BL
servers to format a single line for display.  Otherwise, you'd be embedding
your presentation logic in your BL servers, which is exactly what you said
not to do.


> There'd
> be what? Maybe 5 lines of code per format?  Each screen would call the
> appropriate BL program.  Each screen would have an exfmt, a
> call/with parm,
> and a repeat-or-go-forward decision.  There'd be... maybe 40 to 80 calc
> lines total for the program?  Maybe 8 hours work?

In my opinion, you're confusing a presentation logic server with a BL
server.  This presentation layer is very specific to the type of UI,
although there could be a large amount of overlap.

Let's for instance take an order line.  Let's say that you want to have
order number, line number, item, quantity ordered, quantity shipped, unit
price and extended price.  This information comes from various places.  This
is presenation format, and I don't expect to write a different BL server for
each format.

The logic in the presnetation program, therefore is enough that the binding
question is still valid.  Even if it were only a few lines, though, I'd
still want to answer the question, because I wouldn't want all the screens
in one program - I'd want them in separate modules of some kind (callable
programs being modules in this sense) so that they could be invoked by other
parts of the workflow.