Anyone using Triggers to enforce data validation & business rules?

Several pages in the new "modernization" redbook cover this topic. Rules
are written only once rather than embedding them in multiple applications
(ILE, Java, PHP, Ruby, .Net). The system enforces them, so you can't get
around them via utilities (such as DFU).

This idea makes sense to me from an architectural perspective. But I'm
struggling with exception handling.

I'm following Trigger coding examples from the following redbook:

http://www.redbooks.ibm.com/redbooks/pdfs/sg246503.pdf

Examples show using the QMHSNDPM API to signal *ESCAPE type messages. That
was causing a spooled program DUMP with every data validation exception - I
finally figured out how to prevent that.

I seems harsh to signal an exception which abnormally ends the Trigger
program - just for data validation errors. Error message appear in job
logs. But how do you get them to appear on the user's screen?

Nathan.