Godmar,
Ok, now I understood what you mean. This ability to use Maps as a "special" type of facts requires the implementation of what we call "pluggable fact types". It is something we wanted to have for ages, but it is not implemented yet. Unfortunately it is not as "easy" as it may appear, but definitively it is a must have for the future, specially as we move to the ontology space.
You are right to think that this will give us another level of expressive power. Among several other advantages, it would allow the the user instead of writing patterns like:
Map( this.factType == "SomeFactType", ... )
Where "factType" is a key in the Map, to simply write rules:
SomeFactType( ... )
More than that, once we have such feature, we can directly use any structure mappable into a Java class as a fact, like Grrovy/Jython/Whatever beans, CSV files, XML documents, etc.
So, it is REALLY powerful and really cool!
Our only limitation is indeed "(wo)man power"... :)
Seriously speaking, we already have pluggable dialects, pluggable evaluators and an "almost pluggable" extractor framework. All of them are pre-reqs for the pluggable fact types, but we did not reached that point yet.
Talking about the project, the team is now committed to deliver support to CEP applications (including temporal reasoning and stream management), support to higher levels of ruleflow and process modeling, improving the whole BRMS and repository tools, plus we have Master Degree and PhD students working on Machine Learning, Decision Trees, Uncertainty Reasoning, Temporal Reasoning and Rulebase Static Analysis.
As you can see there is a LOT on our plate, so if anyone wants to step up and help us accelerate the development of pluggable fact types, it is more than welcome.
ANYONE up to the task? :)
Regarding your question about the removal of shadow fact, yes, it is scheduled for the next major release in a few months time. Although, it is import to remember that you can already disable shadow facts, just by following some requirements. I will write another e-mail about that.
[]s
Edson
2008/2/20, Godmar Back <godmar@gmail.com>:
I think that you *should* treat facts that implement java.util.Map
differently from other facts.
Ignore their concrete class and don't worry about applying your
shadowing algorithm.
Then, treat them as if they were beans with getXYZ() methods for each
key "XYZ" they contain.
Your reply indicates that you haven't even considered this design. I
wonder why not? (It seemed so natural to me that I assumed it's what
Drools *must* do. Especially considering the fact that Drools's chosen
scripting language, MVEL, supports accesses to maps using a special,
javascript-like syntax that allows you to verify that accesses are
side-effect free.)
On Wed, Feb 20, 2008 at 4:11 PM, Edson Tirelli <tirelli@post.com> wrote:
>
> A blog I wrote a long time ago about dynamically generated beans:
>
> http://blog.athico.com/2006/12/dynamically-generated-class-beans-as.html
>
I'm aware that I can generate beans - dynamically or statically, but
that is exactly the hassle I had hoped to avoid. (And, quite frankly,
it's not something I should have to go through when using a framework
such as Drools.)
Will the issue disappear in a future, shadowless version of your
engine? To what degree will this version depend on facts being
conforming Java beans?
- Godmar
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Edson Tirelli
JBoss Drools Core Development
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