Re: Web Services Adapter for 5250 Applications

[Joe Pluta <joepluta@xxxxxxxxxxxxxxxxx>]

Nathan Andelin wrote:
> Joe,
>
> Let's see if I get the jist of this.  To use 5250 applications under a 
> Web services architecture you're suggesting a middleware "adapter" that 
> bridges the differences between programs that control display file I/O 
> and a Web services client?
>   
Correct.  The adapter will in effect encapsulate an interaction between 
a user and the software.  You can think of it as a sophisticated 
keyboard macro.
> I'm still pretty skeptical.  It seems like the middleware adapter could 
> get unwieldy.
It really depends on your software and your processes today.  If the 
process to add an order is simple and streamlined, then the adapter will 
similarly be streamlined.  If however your process requires accessing 
several programs and lots of screens, then the adapter will be similarly 
complex.

> But it sounds like it may be worth comparing to Scott's 
> suggestion to break out business logic in 5250 programs and turn them 
> into callable procedures.
>   
The point is that this provides an interim step.  By using an adapter to 
convert the 5250-based process into a callable procedure, you have done 
the first half of what Scott suggested.  The nice thing is that a lot of 
this part of the conversion can be automated, and the ROI is easily 
apparent because there are no fundamental changes to existing business 
logic.

Then you can pick and choose which business processes you want to really 
rewrite, and concentrate your resources on extracting the business logic 
from those.  This is always the more time consuming part.  By using this 
staged approach you can quickly put a new interface in front of your 
users, and then extract business logic as circumstances dictate.

> IBM's IWS product is designed to interface with callable procedures.  It 
> generates PCML and WSDL interfaces between Java clients and ILE programs 
> and procedures.  Clients "call" procedures.  I/O is handled via program 
> parameters.
>   
Since most 5250 programs aren't callable, this doesn't work very well.

> IIRC, Zend 5250 bridge provides an interface between PHP scripts and the 
> Webfacing server to enable PHP applications to talk to 5250 programs. 
> It generates names for fields that map to display file fields, and 
> enables PHP scripts to reference and update those fields.  To me, that's 
> unweildy.
>   
Why?

Joe