[rules-dev] Decision Tables + Templates: Consistency please!

[Michael Anstis]

Hi,

I opened myself a good can of worms yesterday.

The long and short of it is the following behave differently (with regard
to the DRL generated):-

   - XLS Decision Tables
   - Templates
   - KIE-WB Guided Decision Tables
   - KIE-WB Guided Decision Table Template fragments

There is a further complication:
https://bugzilla.redhat.com/show_bug.cgi?id=996964


All of the listed rule types currently discount a constraint if it#s value
is empty, or value.trim() is empty. The requirement really only affects
String field types. The difficulty is how to differentiate between a
null-value (empty cell) and empty-string that works consistently with XLS
and the KIE-WB editors.


So, my question is what behaviour should we standardize on?

I propose the following:

   - For a Pattern, with no constraints we exclude the pattern (this is
   current XLS behaviour).

e.g. Person( name == $name, age == $age ). If we don't provide values for
$name and $age we don't include the Person pattern. If a user wants to
include the Pattern they'd need to add a constraint "this != null".

If we include the pattern when there are no constraints then it is more
difficult to provide a work-around to exclude the pattern if this is what
some users need (and since it's the existing behaviour; less likely to be
an issue for the majority of XLS users).


   - Support escaping String literals with quotes; so a user would enter ""
   or "   ". This make it obvious that the cell contains a non-null value. The
   surrounding quotation marks would be stripped before being used in the DRL.


WDYT? Should I put this out to the community for opinions too?

With kind regards,

Mike
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