[rules-users] Removing facts from statefulknowledgeSession's memory

[Wolfgang Laun]

Just in case anybody wonders about the effort for building a mechanism for
retracting facts based on fact attributes or other data, I outline the
solution I have implemented.

My class FactWiper implements WorkingMemoryEventListener and Runnable.

   - The implementation of objectInserted( ObjectInsertedEvent event )
   determines whether the object needs handling and, if so, the retraction
   Date, based upon whatever strategy you care to implement, e.g., reflection
   method call, Map<Class,Long>, etc. If it is to be handled, it signals
   Condition "change" to the thread.
   - A SortedMap<Date,Object> expiry2fact keeps track of pending
   retractions.
   - The thread loops into an awaitUntil( x ) on the "change" condition,
   where x is (generally) the first retraction Date. If reached, it retracts
   according to the foremost Map entry; if signalled it reasesses the situation
   and reenters the awaitUntil.

-W


2010/11/12 Michael Anstis <michael.anstis at gmail.com>

> A time based eviction queue is simply a queue that evicts its content based
> upon time-based heuristic. So the WorkingMemoryEventListener would store
> facts inserted into the WorkingMemory in an internal queue and evict them
> from that queue based upon some time-based heuristic. You could use an
> Executor (ScheduledExecutorService) etc to remove facts from the queue and
> working memory at set intervals.
>
> With kind regards,
>
> Mike
>
> On 11 November 2010 22:31, Ayush <ayush.vatsyayan at alcatel-lucent.com>wrote:
>
>>
>> Can you please elaborate on "Have it store each inserted object in a
>> time based eviction queue and it'll remove things for you." i.e. how can I
>> do it?
>> --
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