Re: [rules-dev] RFC: stream concept
On 26 July 2011 21:42, Edson Tirelli <ed.tirelli(a)gmail.com> wrote:
Hi all,
As you all know, we use "entry-points" to represent streams in Drools,
but in fact, entry points are a much more general abstraction than just
streams. For instance, they create partitions in the RETE's alpha network,
they support all Rete concepts like truth maintenance, they share a
centralized fact handle factory (that is possibly a contention point), etc.
Event Streams in general can have a much more specialized
implementation. For instance, as events are immutable,
"Immutable" certainly not by a Drools definition? Something with
@role(event) is just a fact, and I can modify an event as required by my
application.
there is no need for truth maintenance;
A fact derived from events could be managed by the TMS - why not? Or do you
mean s.th. else?
streams should be 100% parallelizable (does this word exist?);
If it didn't exist before, it exists now ;-)
some algorithms like event sequencing can be run before injecting
events
into the main engine instead of injecting and then coordinating back with
the sequencing algorithm.
Because of things like the ones above, I was considering creating an
explicit concept for streams in Drools. They would be a first class concept
in the engine and would be handled appropriately. They would be orthogonal
to entry-points, and be used exclusively for events.
It's difficult (for me) to see what a "stream" should imply. Can you
provide
a concise definition? A "stream" should be for role event only, and its
facts should be immutable (?) - what else?
Are there any good use cases for these "streams" that cannot be readily
dealt with using events?
The other option that we have would be to continue to hide the
implementation behind the concept of entry-points and to select algorithm
details by compile time analysis. Although it seems like a simpler solution,
it has the potential of confusing users
Most of the time, the confusion of Drools users stems from the lack of clear
documentation - not from the complexitiy of features.
Cheers
Wolfgang
that would not know exactly when something is being executed as a
regular
entry point (with TMS, and all the stuff mentioned above) or as a specific
stream (that has features that would be specific for events).
Thoughts?
Edson
--
Edson Tirelli
JBoss Drools Core Development
JBoss by Red Hat @ www.jboss.com
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