Retraction

Stacy

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Dec 14, 2011, 9:49:04 PM12/14/11

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I have seen discussions in the past about the possibility of allowing
retractions of asserted facts. Has anyone tried to implement that?

Bruce Frederiksen

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Dec 15, 2011, 11:35:18 AM12/15/11

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Not I. It has been asked for a lot, so I'd like to encourage somebody to take a shot at this! If so, I am always available for questions.

-Bruce

On Wed, Dec 14, 2011 at 9:49 PM, Stacy <stacym...@gmail.com> wrote:

I have seen discussions in the past about the possibility of allowing
retractions of asserted facts. Has anyone tried to implement that?

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Stacy

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Dec 15, 2011, 8:00:56 PM12/15/11

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I am willing to take a look at doing it when i have some time but
don't want to approach it blindly.
Do you have suggestions as to how to approach it?

Bruce Frederiksen

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Dec 17, 2011, 7:02:01 PM12/17/11

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There are three aspects:

Should retracting fact A also retract any other facts asserted by forward chaining based on fact A? I think that the answer to this is no.
Should retracting fact A cause forward chaining rules with a "notany A" to fire immediately. I'm less certain on this one, but would lean towards yes.
The remaining aspect is to keep the fact_list caches up to date. Look at the add_args method in the fact_list class in pyke/fact_base.py to see how facts are added to the cache (self.hashes is the cache and is kept in the fact_list object).

This work should be done in the "pyke" hg repository.

You will need a sourceforge ID to be able to commit to the repository. If you give me your sourceforge username, I would be happy to add you to the project!