Re: [drools-dev] Accessing fact fields using OGNL

[Mark Proctor]

Full integration is extremely difficult because we cannot monitor nested objects. The Rete network maintains an internal state of the relationship between  facts, if those nested objects change the  Rete network loses its integrity. To understand why think about HashMaps, if you put an object and they change the value of the key  - thus changing the equals and hashcode - you can no longer retrieve that object by the key. We have this same issue. As  a compromise we allow people to do what they want inside  of  predicates and evals as we retain  no  state on those. One option we are considering is using JFDI to allow field  type constraints with nested objects and simply converting that to a predicate during the parser stage. Its sugar coating, but should help improve declarative coding. Michael Neale wrote: Hi Alex. We are currently working on something similar (but a little more tuned for rules) but the end result will be pretty much the same result (but hopefully more performant, and with rule specific features like handing the shadow facts, deftemplates transparently etc). We could certainly use some help with that. Bob Mc is heading up that, and we have it in a seperate codehaus repository at the moment (more unit tests/enhancements needed). Unforatuntely, integrating into the drools code would require both some understanding of the drools compiler code, but we also haven't 100% decided how we will integrate yet, but please, do feel free to dive in. you can find the details: http://xircles.codehaus.org/projects/jfdi On 11/3/06, Alexander Varakin <[EMAIL PROTECTED]> wrote: Hi, There were some discussions on the list about using Maps as fact objects. I think it would be a very good idea to implement this requirement using OGNL (Object Graph Navigation Language) library. This library allows accessing members of java beans, maps, collections using simple expressions. It also supports nested objects. I am working on a project which would benefit from implementing this feature and I am willing to commit some time/resources to this job. I would really appreciate if somebody will give me: 1. some pointers to how to implement this feature 2. approximate time estimate for implementing this, assuming that developer is not familiar with source code of Drools Thanks, Alex Varakin --------------------------------------------------------------------- To unsubscribe from this list please visit:      http://xircles.codehaus.org/manage_email