2011/2/3 Esteban Aliverti <esteban.aliverti@gmail.com>

Hi,

1) You write a java program, rules / actions are hard coded inline or saved
in text files / excel sheets / XML files etc. After importing the necessary
drools classes you call the drools interface routines, with the following
functionalities:
load rules, providing working memory, adding facts und finally starting the rule
engine (e.g. firing rules).

Just some corrections here. The steps would be: load rules, get a working memory (kbase), create a session from the working memory, insert facts to it (this will start the pattern matching algorithm), fire the action part of the rules that matches the inserted Facts.

The working memory is the knowledge session (not the kbase) where all your facts will live.
The main advantage of this approach is to have the business rules / logic decoupled from your application and declarative expressed.
Remember that the rule engine will not evaluate the rules in a sequential order (in contrast with IF and CASE statements) and the rule engine design was conceived thinking to handle huge amount of rules and the evaluation of these rules are optimized.

2) You use the capabilities of the Drools GUI tools (such as Guvnor), which
allows entering rules, objects and actions via GUI tools.
Here, I don't get the point whether a part of the java code is generated
automatically, or whether you have to write your java classes by yourself, as
presented in possibility 1 (above), but without coding the rules by yourself in
the source code / external input files.

Guvnor is just used as a centralized place to create (if you want to), maintain and distribute your rules. You have different editor for different representations, like DRL, BRL (using a Guided Editor), Decision Table, DSL, etc. Guvnor then exposes these assets (their source code or binary representation) through different URLs. So, your application should read the rules (in the first step of the previous section) from Guvnor using HTTP (or even webdav) to create the working memory.

Hope this helps to clarify a little bit your thoughts.

Best Regards,

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Esteban Aliverti
- Developer @ http://www.plugtree.com
- Blog @ http://ilesteban.wordpress.com

On Thu, Feb 3, 2011 at 2:26 PM, Martin Richardsen <jaichwill@gmail.com> wrote:

I am a complete novice concerning Drools and have some basic questions,
which arised after studying the drools documentation and some examples as well.

As far as I got it right, you have two possibilities to work with drools

1) You write a java program, rules / actions are hard coded inline or saved
in text files / excel sheets / XML files etc. After importing the necessary
drools classes you call the drools interface routines, with the following
functionalities:
load rules, providing working memory, adding facts und finally starting the rule
engine (e.g. firing rules).

2) You use the capabilities of the Drools GUI tools (such as Guvnor), which
allows entering rules, objects and actions via GUI tools.
Here, I don't get the point whether a part of the java code is generated
automatically, or whether you have to write your java classes by yourself, as
presented in possibility 1 (above), but without coding the rules by yourself in
the source code / external input files.

I would be very pleased, if anyone could explain me the essential difference
between the two approaches and accordingly tell me what the advantage of using
method 2) would be in contrast to method 1), particularly concerning the
necessary java coding.

---

Well and there would be another question, if you write down your rules and the
corresponding software, which accesses the rules, is it possible to add some
rules later, without rewriting/recompiling your software?

Thanks in advance!

Cheers, Martin.

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