[rules-users] Web decision tables (Guvnor)

[Michael Anstis]

Hi Stephen,

You've made my afternoon ;)

The operation of "otherwise" is rather dumb. It does not have any
understanding of what groups of rows it is meant to limit it's search of
values to construct the "not in...." part.

As you have discovered, in your case, the Account column has no
significance at all (to the web-guided decision table) although it does to
the business analyst.

The immediate workaround would be to move each "group" to a different
decision table; i.e. Account=1 and Account=2. I appreciate your example is
probably a simplification of the real problem.

A better solution would be to furnish the "otherwise" value with the
information it would need to determine it's search range. e.g. define
"otherwise" with a key column of "Account". This is however an enhancement
:(

Feel free to raise a JIRA (for GUVNOR)... no promises as to when I'll get a
chance to do anything about it though :(

More complex requirements exist, for example given:-

Account Qualifier Currency   CanTrade
   1      A         EUR         Y
   1      A         USD         Y
   1      B         IDR         Y
   1      A       Otherwise     N
   2      A         EUR         Y
   2      B         USD         Y
   2      B       Otherwise     N

Account=1, Qualifier=A, Otherwise = not in ("EUR", "USD")
Account=1, Qualifier=B, There is no otherwise
Account=2, Qualifier=A, There is no otherwise
Account=2, Qualifier=B, Otherwise = not in ("USD") etc

So "Otherwise" will need a set of key\group columns.

With kind regards,

Mike

On 10 August 2012 15:50, Stephen Masters <stephen.masters at me.com> wrote:

> Hi folks,
>
> Given a decision table a bit like this (hopefully the monospaced font lays
> it out ok!):
>
> Account Currency CanTrade
>    1       EUR       Y
>    1       USD       Y
>    1       IDR       Y
>    1     Otherwise   N
>    2       EUR       Y
>    2       USD       Y
>    2     Otherwise   N
>
> LHS conditions are generated a bit like this:
> account == 1, currency == 'EUR'
> account == 1, currency == 'USD'
>         account == 1, currency == 'IDR'
> account == 1, currency not in ('EUR', 'USD', 'IDR')
> account == 2, currency == 'EUR'
> account == 2, currency == 'USD'
> account == 2, currency not in ('EUR', 'USD', 'IDR')
>
> … which has the effect that for account 2, currency IDR, the rule does not
> fire. For the business analysts building the rules, this does't make a lot
> of sense, as they're expecting it to mean:
> account == 2, currency not in ('EUR', 'USD')
>
> Unfortunately this means that if a currency is permitted for one account,
> then a row must be added for every other account, indicating that the
> currency is not permitted.
>
> I'm trying to achieve a sensible default (fire the rule to reject the
> trade) unless the currency is explicitly permitted.
>
> Is there a decent mechanism for achieving this in a decision table?
>
> One alternative I can think of is to create a technical rule which
> logically inserts a rejection which exists as long as this rule hash't
> fired. But I would really prefer to avoid doing anything like that, as I
> reckon it would be something of a maintenance nightmare.
>
> Any thoughts?
>
> Cheers,
>
> Steve
>
>
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