[rules-users] Inferencing

[Tim de Jager]

Thank you this explains it. As I see it the Visual Rules approach is very different in that it's more of a flowchart based approach than actual inferencing. And it's clear now that there is no difference in the infreasoning inferencing process either interpreted or compiled.

Also interesting read about the Airliner application Greg, thanks!

-----Oorspronkelijk bericht-----
Van: rules-users-bounces at lists.jboss.org namens Edson Tirelli
Verzonden: ma 8-3-2010 22:33
Aan: Rules Users List
Onderwerp: Re: [rules-users] Inferencing
 

   I don't know much about Visual Rules so I will abstain from commenting on that (although I can imagine what they are doing). 

   Regarding "interpreted" vs "code generated" RETE, there should be no difference at all on the reasoning process, as the rules would be the same, does not matter if it is "compiled" or "interpreted". 

   There **could** be difference on the dynamic behavior of the knowledge base itself, i.e., adding/removing rules while there are sessions running. Some engines that use the compiled approach require the whole rulebase to be recreated (and obviously the corresponding sessions) every time a rule changes or is added/removed to/from the kbase. Talking about Drools itself, our goal is to remain completely dynamic, even when compiling down to bytecode, and we do that by using custom classloaders that allow us to add/remove rules and properly update any existing sessions on-the-fly. Although, it is important to note that as it is today, Drools does not bytecode generate all of the kbase (as I mentioned before, we use a mixed approach). We are capable of bytecode generating all but the beta network as it is today, and we will add support for that in coming versions.

   It is important to note, though, that one approach is not essentially better than the other. There are advantages to both approaches and in case of Drools, the idea is to keep them both and hopefully add heuristics that will allow us to transparently JIT compile only the parts of the network that would benefit the use case the most, while keeping the non-compiled approach for the rest. By transparently I mean, without the user having to worry about this.

   Drools sequential mode is a change on the Rete algorithm that is ***not*** transparent. I.e., depending on what you are doing, results might be completely different when running ReteOO (a general purpose algorithm with inference) and the Sequential mode. You may think about the sequential mode as a non-inferencing algorithm.

   From all the discussion, I hope it is clear that the functional requirements of an inference algorithm should not change when running in compiled or interpreted mode (and that is why I called it an "orthogonal concern). But, of course, there will probably exist differences on the non-functional requirements.

   []s
   Edson

   


2010/3/8 Tim de Jager <tim.dejager at student.hu.nl>





	Thanks a lot everybody for their awnsers, this clarifies it to some extend :)!
	
	What I was talking about was indeed the difference between an: interpreted rete engine vs. code generated rete engine vs. the use of no inference engine at all (e.g. Visual Rules). One of the questions that pop up: Is it possible to maintain the same 'statefull' features with a code generated inference engine? Like you said Take generates a backward chaining algorith, but would it be able to react to a changed fact like drools can with the modify statement? Is code-generated Rete maybe comparable with the drools sequential mode?
	
	It could be that I'm mixing alot of things up, I can't find a whole lot on this subject.
	
	So do you have any insight on the differences between a interpreted rete engine an a code generated one. Would they differ in functionality in any way?
	
	Thanks!
	
	-----Oorspronkelijk bericht-----
	Van: rules-users-bounces at lists.jboss.org namens Edson Tirelli
	Verzonden: ma 8-3-2010 17:55
	Aan: Rules Users List
	Onderwerp: Re: [rules-users] Inferencing
	


	  Hi Tim,
	
	  That is a nice topic for studies, but be prepared for a tsunami of information and quite a few controversies. :)
	
	  Regarding your question, I am not sure I completely understand what you mean, but it is important to be clear that "generation of code" is an orthogonal concern to the chosen algorithm. I.e., take the Rete algorithm for example: you can have it fully "interpreted" (I am using the term loosely here), you can generate code for it completely, or you can be anywhere in the middle. In all cases, the properties of the algorithm itself will be preserved (assuming the implementations are correct). Incurring the risk of making a mistake here, I will mention that AFAIK Jess falls in the first cathegory, OPSJ falls in the second and Drools falls in the 3rd, and they are all Rete based algorithms.
	
	  Its been a long time since I last looked at TAKE, but at that time it was generating code for a backward-chaining-like algorithm. Not sure what it has now.
	
	  So, my suggestion is that you either focus on the properties of the algorithms itself (for instance, are you comparing classic Rete with known algorithm like LEAPS, TREAT, etc) or focus on the advantages and disadvantages of code generation (for instance "interpreted Rete" versus "code generated Rete", again using terms loosely here). Mixing everything in a single comparison might be misleading.
	
	  Edson
	
	
	2010/3/8 Tim de Jager <tim.dejager at student.hu.nl>
	
	
	
	       Hi everybody,
	
	       I'm currently doing my bachelor thesis on Rule engines. This includes
	       comapring different Rule engine products. I have set up a small Java program
	       (Conway's game of life) and I'm writing the 'engine' in different Rule
	       engines, while keeping the same GUI,CellGrid etc. I have already made a
	       Drools based engine.
	
	       I have been studying the Rule engine subject for somewhat more then a month
	       now. And I'm currently seeing two different developments namely the use of
	       an inference engine and the generation of embedded code instead (Take,
	       Visual Rules etc.)  I can see some of the pro's and cons with both
	       paradigms. But I'm wondering what opinion some of you guys have on the
	       subject.
	
	       I can see that without inferencing  it is very hard (or even impossible) to
	       keep a statefull session inside the rule engine, haven't seen a
	       non-inferencing rule engine which does offer this possibility. And also lose
	       features like TMS. But what would be a concrete example where a statefull
	       session is absolutely necessary? Instead of letting the engine reason over
	       all the facts in stateless way. And managing conflicts with a ruleflow (see
	       Visual Rules for a nice example).
	
	       I'm looking forward to hearing your thoughts.
	
	       Thanks,
	
	       Tim
	
	       P.S I already read two of Mark Proctors blogs on inferencing, but while
	       enlightening, they didn't supply me with a definitive awnser
	       --
	



-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss by Red Hat @ www.jboss.com


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