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

[Wolfgang Laun]

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.
>
>
>
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