[rules-users] Abstraction between rules and data model?

[Wolfgang Laun]

What you describe can be done with /bin/sed.

Notice that the DSL processor doesn't require you to translate entire
patterns; there is a mechanism for translating "keywords", which is
just arbitrary tokens to whatever replacement text.

If a "bar" must be translated to a "barList" in the context of a class
"Foo" but not in any other context, a more sophisticated translation
is required in any case (with /bin/sed still being sufficient if
patterns aren't split across lines).

Some say that good design makes use of Interfaces, which leaves room
for actual implementations being changed as long as the interfaces are
implemented. Here, note that rules can be written against interface
types.

-W


On 26/05/2014, Péter Gergely, Horváth <h.peter at mailbox.hu> wrote:
> Hi All,
>
> We are evaluating Drools 6 for our use case, and face challenges where we
> would need some ideas from more experienced users of Drools.
>
> We have an application with a massive code base and a large number of model
> (entity) classes. We are in the process of moving away from inherited
> legacy technologies and refactoring the old code base. As a part of this
> work we would like extract some of the hard-coded business logic to
> external rules, that is why we are looking at Drools as a potential
> solution.
>
> What we would like to have is some kind of abstraction or mapping between
> actual entities and rules the business users can define so that they do not
> have to know the _exact_ details of the data model (field names, precise
> relations etc). This would be important for us so that we can refactor the
> old model classes without affecting business rules; also it would make life
> easier for the business users. While IDE support might make refactoring
> easier, we definitely want to have a separation between rules and entities.
>
> Given our situation, writing and maintaining "stable" wrapper/adapter
> classes for the sole purpose of rule processing is out of question. I have
> checked the documentation of Drools DSL support and for me it seems to be
> overkill for our use case: we do not really need a custom language, but
> simply an abstraction between rules and the data model classes.
>
> What I could imagine is a piece of code, (a custom property resolver? - no
> sure how it is called) which maps property expressions to actual properties
> based on a custom annotation on the entity class or something like that, so
> that a rule containing "Foo.bars" expression does not have to change even
> if we decide to rename "Foo.bars" to "Foo.barList" in the model classes.
> (This was just a simple example of a potential use cases)
>
> Could you please share your thoughts on this topic and point me into the
> right direction?
>
> Thanks,
> Peter
>