[rules-users] DSL for multiple 'OR'

[Michael Anstis]

Hi,

Starting from 5.4.0.beta2 you can use BRL fragments in decision tables.

This will allow you to define a column like this:-

$c : Cucumber()
Cucumber( this == $c, numberOfWormHoles > {@holes} )
Cucumber( this == $c, curvaturePerLengthUnit > {@curvature} )
Cucumber( this == $c, hue < {@minHue} || > {@maxHue} )

You will then be presented with columns for each of the "variables" ({@XXX}
in the above).

If you do not specify *all* values for a pattern the pattern will not be
included in the generated rules. For example:-

@holes=0, @curvature=<empty>, @minHue=90, @maxHue=150 would generate:-

$c : Cucumber()
Cucumber( this == $c, numberOfWormHoles > 0 )
Cucumber( this == $c, hue < 90 || > 150 )

You could equally define multiple BRL fragment columns like this:-

Column 1 - $c : Cucumber()
Column 2 - Cucumber( this == $c, numberOfWormHoles > {@holes} )
Column 3 - Cucumber( this == $c, curvaturePerLengthUnit > {@curvature} )
Column 4 - Cucumber( this == $c, hue < {@minHue} || > {@maxHue} )

Resulting in the same operation.

The || requirement makes using a decision table pre-5.4.0.beta2 impossible,
however if you could re-think your logic to use &&'s it is possible but
messier.

With kind regards,

Mike

2012/1/30 Stephen Masters <stephen.masters at me.com>

> Hi folks,
>
> I'm trying to create a DSL (to drive a Guvnor guided editor), for which a
> rule could be written as:
> Given a cucumber
> - containing one or more worm holes
> - or with a curvature greater than 10mm per 10 cm length
> - or with a hue of less than 90 degrees
> - or with a hue of greater than 150 degrees
> Do not put that cucumber on the supermarket shelf
>
> (note: I'm actually developing a banking risk management system looking at
> different types of counterparty ratings, rather than a fruit&veg quality
> control system, but hopefully the above example is more readable!)
>
> Is there a decent metaphor that could be used by a business user in Guvnor
> to manage such rules in one place? Or is it likely to be necessary to
> create multiple rules?
>
> As far as I understand, every condition added to a rule through such DSLRs
> adds itself to the filter. i.e. They are AND rather than OR.
>
> The other metaphor I could think of is the decision table as a neat
> interface for generating multiple rules, but that seems to be geared
> towards creating rules based on multiple values of a single attribute
> rather than multiple conditions.
>
> I'm trying to keep the user interface as simple as possible, so any
> thoughts would be appreciated.
>
> Cheers,
>
> Steve
>
>
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>
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