I have few experiences with Drools, but I don't think that "application data" and static variables are the same.
Application data, if I'm not mistaken, are placed in the working memory by the application client code. Thus, they are not a private state variable of the rule context, but a public exchange entity that rules can use out of their declared parameters. As the name says, they are the "application" responsibility, not the rule context one ! The working memory can be easily instantiated by the client code according to concurrent call, it seems easy to control threading issues... The static variable declared in a DRL function block doesn't seem to be public, since there is no evident (for me) way to get it from outside the rule context. What I don't know, is how Drools generates Java classes from the DRL files, and how resulting objects are created and/or shared by concurrent callers... Once again, some clarification about the better way to keep memory between rules, without any necessary external declarations, such as "application data", is welcome... -- Ephemeris Lappis > -----Message d'origine----- > De : news [mailto:[EMAIL PROTECTED] De la part de Peter Van Weert > Envoyé : mardi 31 janvier 2006 18:38 > À : [email protected] > Objet : Re: [drools-user] Drools: Sharing a value between the rule's > "condition" and "consequence" ? > > I agree, this is a brittle and counter-intuitive technique. Also, > looking at the original problem statement: > > > Please note I know about "application data", but i'd rather not use > > it, because my sqrt is just a temporary value... > > Does storing the value in a static variable solves this? I don't know > the exact semantics of Drools, but my guess is that application data is > essentially the same as a static variable? > > Carriing over computed results from conditions/guards to the > consequences/body/actions is a problem other rule engines also > encounter, and I don't think it can be solved nicely (i.e. without > resorting to global state) without a (small) language extension... > > Yours, > Peter > > > Smith, Philip wrote: > > Rule firing is single threaded so that shouldn't be a problem. However, > > the same static variable could be written to by the evaluation of many > > conditions and as such it could be overwritten before the consequence is > > actually fired. Your rules could be written such this could not happen > > but this remains a brittle technique. > > > > Philip Smith > > [EMAIL PROTECTED] > > (650) 628-7941 (x87941) > > > > -----Original Message----- > > From: sol myr [mailto:[EMAIL PROTECTED] > > Sent: Tuesday, January 31, 2006 8:48 AM > > To: [email protected] > > Subject: Re: [drools-user] Drools: Sharing a value between the rule's > > "condition" and "consequence" ? > > > > Thanks very much for this reply :) > > However, I was wondering: will it work in a multi-threaded environment > > ? > > I have a Servlet, where each HTTP request is handled by a separate > > thread, as usual. > > All those threads use the rule engine, simultaniously... if it's a > > static variable, won't they override each other's data ? > > > > Thanks again > > Sol > > > > > > > > Ricardo Rojas Aguirre <[EMAIL PROTECTED]> wrote: > > Hi, I solved the same problem with a local variable defined in the > > function > > tag... > > > > To solve your proble try somthing like this... > > > > > > public static double sqrtResult; > > > > > > > > > > > > < parameter identifier="num" > > > < class > Integer < / class > > > < / parameter > > > > > < java:condition > > > (sqrtResult=Math.sqrt(num.intValue())) > 1000 > > < / java:condition > > > > > < java:consequence > > > System.out.println( sqrtResult ); > > < / java:consequence > > > > > > > > > Cheers > > Rik > > > > > > ----- Original Message ----- > > From: "sol myr" > > To: > > Sent: Tuesday, January 31, 2006 11:04 AM > > Subject: [drools-user] Drools: Sharing a value between the rule's > > "condition" and "consequence" ? > > > > > > > >>Hi, > >>I'm new to Drools. Could anyone please help with the following: > >> > >>Can you share data between a rule's "condition" and "consequence" ? > >>For example: > >>- My "condition" calculates some square root (Math.sqrt) > >>- The "consequence" needs to print out the same square root > >> > >>It's not efficient to call Math.sqrt twice... : > >> > >>< parameter identifier="num" > > >>< class > Integer < / class > > >>< / parameter > > >>< java:condition > > >>Math.sqrt(num.intValue()) > 1000 > >>< / java:condition > > >>< java:consequence > > >>System.out.println( Math.sqrt(num.intValue()) > >>< / java:consequence > > >> > >>Is there a way to store the result of "Math.sqrt" in some temporary > >>variable ( so as to avoid the duplicate calculation ) ? > >>Please note I know about "application data", but i'd rather not use > > > > it, > > > >>because my sqrt is just a temporary value... > >> > >>Thanks :) > >> > >> > >>--------------------------------- > >> > >>What are the most popular cars? 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