[rules-users] How to do validation of facts in a Stateful Session?

[Wolfgang Laun]

Two ways for getting data out from the engine's munching:

(1) You set up a global object alertUser which provides just that service,
so it can be done with a rule:

rule "x"
when
   $ve : ValidationError()
then
   alertUser.notify( $ve );
   retracT( $ve );
end

(2) You run a query from Java code after return from fireAllRules

query "allValidationErrors"
  $ve : ValidationError()
end

The Java code for running the query is in the Expert manual. You
can, of course, retract just as well from Java.

-W


On 12 August 2010 10:45, Stephen Mcgruer <s0840449 at sms.ed.ac.uk> wrote:

> Apologies, where I use (Java) I do indeed mean the Java code between
> calls to fireAllRules(). I'm not entirely sure about how you meant to
> do it in rules, but how do you then report back to the user that there
> is a problem? The Java code that calls fireAllRules() has to be able
> to get errors and then pass them back to the webpage (yay for a
> project structure which requires me to communicate with the front end
> by generating XML JSP pages as replies to URL requests from the PHP
> code which runs the website...)
>
> Cheers,
> Stephen
>
> Quoting Wolfgang Laun <wolfgang.laun at gmail.com>:
>
> > By "(Java)" do you mean Java code between calls to fireAllRules() or Java
> > code
> > in RHS? I think that what you describe in items 5, 6 and 7 can very well
> be
> > written as rules, based on a Validation object inserted at the time the
> > actual
> > operation is done in WM. It should contain:
> >    - links to the old, or new, or both, Fact objects
> >    - the validation status (OPEN, VALID, INVALID)
> >
> > Need a more detailed outline?
> >
> > -W
> >
> > On 12 August 2010 10:08, Stephen Mcgruer <s0840449 at sms.ed.ac.uk> wrote:
> >
> >> Hi there,
> >>
> >> My project uses Drools to (among other things) validate new
> >> facts/updates to old facts, according to a set of rules. (For example,
> >> we might have a rule that says "No two people can be named the same
> >> thing".) Our method of validation and error reporting was originally
> >> chosen for a stateless session (before we had the requirement of doing
> >> checks like the above), and I feel I've had to hack it a bit much to
> >> get it working with stateful sessions. The current methodology is:
> >>
> >> 1. (Website) The user inserts/updates a fact.
> >> 2. (Java) If the fact is new, an object is created for it. If it is an
> >> update, the pre-existing object is fetched from the object repository
> >> (the interface to the database) and a backup copy of the object is
> >> taken.
> >> 3. (Java) This fact is either inserted into the KnowledgeBase (KB) or
> >> a pre-existing fact in the KB is updated depending.
> >> 4. (Rules) If the new/updated object fails a validation rule, it will
> >> be retracted and a ValidationError object will be inserted into the KB.
> >> 5. (Java) The code then searches for ValidationError objects that
> >> match the just inserted/updated object. If it finds any it records
> >> them and then retracts them from the KB.
> >> 6. (Java) If there are no errors, then that's it - a success report is
> >> generated and passed back to the website.
> >> 7. (Java) If there were errors, then if the user was updating a fact
> >> the backup of it (before the changes) is inserted back into the KB.
> >> The website is then passed a failure report.
> >>
> >>
> >> It just feels very hacky to do so much manual insertion/retracting
> >> from the Java side of the code.
> >>
> >> So, is there a 'correct' way to do stateful validation? And does our
> >> current way even work, or are there hidden problems that we've not
> >> spotted?
> >>
> >> Cheers,
> >> Stephen
> >>
> >> --
> >> The University of Edinburgh is a charitable body, registered in
> >> Scotland, with registration number SC005336.
> >>
> >>
> >>
> >> _______________________________________________
> >> rules-users mailing list
> >> rules-users at lists.jboss.org
> >> https://lists.jboss.org/mailman/listinfo/rules-users
> >>
> >
>
>
>
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>
>
>
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