RE: [rules-users] calls to 'Helper' classes in LHS - are they all owed?
Thanks, Mark. Are there any plans on making return value, predicate and eval expressions indexable (in case it is possible at all)? Would it be included in 3.2 release? I understand that DROOLS can not guarantee that helper method will return the same value each time and probably that's why excludes such cases from index, but the same goes for 'getters' of the fact objects - DROOLS can't guarantee the getter will return the same value each time, so it just have to assume it (and it is outlined in the documentation). There are a few use case that might need this kind of functionality, eg to cache the results of 'associative' lookup. Especially for the 'Decision Tables'. The problem I'm facing right now is I need to 'expand' the list of codes based on some id and use those codes as constraint: MyObject(field = LookupMap.getCodes($param)) Where $param is a value from Decision Table data. In this particular case a set of, say 100 codes, can be described with a simple ID. For more complex cases a pseudo 'set select' expression can be passed as a parameter (eg, LookupMap.getCodes(groupId_1 - grouperId_2), which should return the intersection of codes in groupId_1 and groupId_2). In any case, the key, value pairs returned by LookupMap class would remain the same. Vlad _ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mark Proctor Sent: 12 February 2007 19:16 To: Rules Users List Subject: Re: [rules-users] calls to 'Helper' classes in LHS - are they allowed? We were hoping the community would work with us and improve the documentation over the last year - to date we have had zip :( We will have another documentation drive once we get to the candidate release stage for the current development cycle. We simply don't have the cycles to work on a book, with any luck after we spend 3 to 4 weeks on documentation during hte candidate release stage it should get better, and maybe one day the manual can form the basis of a book. Some ideas for the community to work include the examples in drools-examples, they can even use what I did for drools 2.x as a starting basis, or to provide a really good tutorial on the basics of pattern matching, you can look the public domain clips manual for pointers here. It's not money we need, its time, YOUR time :) If you want to use a helper class it must be in a return value, predicate or eval - none of which are currently indexed. return value and predicate must also be time constant, eval does not have to be. Mark Michael Suzio wrote: I see this in the docs: A d0e1997Predicate constraint can use any valid Java expression as long as it evaluated to a primitive boolean - avoid using any Drools keywords as Declaration identifiers. Previously bound declarations can be used in the expression. Functions used in a Predicate Constraint must return time constant results. and under the discussion of 'eval': Evals cannot be indexed and thus are not as optimal as using Field Constraints. and this in general discussion of constraints and accessors of your objects used in them: Do please make sure that you are accessing methods that take no parameters, and are in-fact accessors (as in, they don't change the state of the object in a way that may effect the rules - remember that the rule engine effectively caches the results of its matching inbetween invocations to make it faster). So, if invoking a helper method is like an eval, I'm thinking Drools computes the match, but then throws it away because it knows this is not a constant expression. Whereas, if it were just a match of an accessor's value vs. a constant String, it could cache that. I'm wildly speculating, only because I want to understand fully what is happening, so I'm throwing stuff out there so the Drools team will have to correct my misapprehensions before I confuse the whole list (*g*). Sometimes reading the Drools documentation is like a Talmudic scholar trying to find the deeper meaning of the sacred words... as much as I want the 3.2 milestone, I want real documentation even more (and *hint hint* -- would probably be willing to pay for it, guys! Can we get an O'Reilly book?) --- Michael On 2/12/07, Steven Williams [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] wrote: I believe there is a caveat on functions and helper methods called from the LHS that they need to be constant over time (or at least over the life of the working memory) which then allows matches to be computed as per normal. Steve On 2/13/07, Michael Suzio mailto:[EMAIL PROTECTED] [EMAIL PROTECTED] wrote: The JBoss guys can correct me if I'm wrong, but although I think that works, what you've just done is eliminate any chance to precompute matches and trim down the checks that need to happen to find a rule match. Since the engine can't know that Helper.transform(value) returns a constant value, it has to re-run that every time and it has to reject for matches to the rule
Re: [rules-users] calls to 'Helper' classes in LHS - are they all owed?
In theory they can be indexed, but we havne't done it yet, no idea when we'll get time. Patches welcome :) Mark Olenin, Vladimir (MOH) wrote: Thanks, Mark. Are there any plans on making return value, predicate and eval expressions indexable (in case it is possible at all)? Would it be included in 3.2 release? I understand that DROOLS can not guarantee that helper method will return the same value each time and probably that's why excludes such cases from index, but the same goes for 'getters' of the fact objects -- DROOLS can't guarantee the getter will return the same value each time, so it just have to assume it (and it is outlined in the documentation). There are a few use case that might need this kind of functionality, eg to cache the results of 'associative' lookup. Especially for the 'Decision Tables'. The problem I'm facing right now is I need to 'expand' the list of codes based on some id and use those codes as constraint: MyObject(field = LookupMap.getCodes($param)) Where $param is a value from Decision Table data. In this particular case a set of, say 100 codes, can be described with a simple ID. For more complex cases a pseudo 'set select' expression can be passed as a parameter (eg, LookupMap.getCodes(groupId_1 -- grouperId_2), which should return the intersection of codes in groupId_1 and groupId_2). In any case, the key, value pairs returned by LookupMap class would remain the same. Vlad *From:* [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] *On Behalf Of *Mark Proctor *Sent:* 12 February 2007 19:16 *To:* Rules Users List *Subject:* Re: [rules-users] calls to 'Helper' classes in LHS - are they allowed? We were hoping the community would work with us and improve the documentation over the last year - to date we have had zip :( We will have another documentation drive once we get to the candidate release stage for the current development cycle. We simply don't have the cycles to work on a book, with any luck after we spend 3 to 4 weeks on documentation during hte candidate release stage it should get better, and maybe one day the manual can form the basis of a book. Some ideas for the community to work include the examples in drools-examples, they can even use what I did for drools 2.x as a starting basis, or to provide a really good tutorial on the basics of pattern matching, you can look the public domain clips manual for pointers here. It's not money we need, its time, YOUR time :) If you want to use a helper class it must be in a return value, predicate or eval - none of which are currently indexed. return value and predicate must also be time constant, eval does not have to be. Mark Michael Suzio wrote: I see this in the docs: A Predicate constraint can use any valid Java expression as long as it evaluated to a primitive boolean - avoid using any Drools keywords as Declaration identifiers. Previously bound declarations can be used in the expression. Functions used in a Predicate Constraint must return time constant results. and under the discussion of 'eval': Evals cannot be indexed and thus are not as optimal as using Field Constraints. and this in general discussion of constraints and accessors of your objects used in them: Do please make sure that you are accessing methods that take no parameters, and are in-fact accessors (as in, they don't change the state of the object in a way that may effect the rules - remember that the rule engine effectively caches the results of its matching inbetween invocations to make it faster). So, if invoking a helper method is like an eval, I'm thinking Drools computes the match, but then throws it away because it knows this is not a constant expression. Whereas, if it were just a match of an accessor's value vs. a constant String, it could cache that. I'm wildly speculating, only because I want to understand fully what is happening, so I'm throwing stuff out there so the Drools team will have to correct my misapprehensions before I confuse the whole list (*g*). Sometimes reading the Drools documentation is like a Talmudic scholar trying to find the deeper meaning of the sacred words... as much as I want the 3.2 milestone, I want real documentation even more (and *hint hint* -- would probably be willing to pay for it, guys! Can we get an O'Reilly book?) --- Michael On 2/12/07, *Steven Williams* [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] wrote: I believe there is a caveat on functions and helper methods called from the LHS that they need to be constant over time (or at least over the life of the working memory) which then allows matches to be computed as per normal. Steve On 2/13/07, *Michael Suzio* [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] wrote: The JBoss guys can correct me if I'm wrong, but although I think that works, what you've just
