Issue 159 in soar: Identical justification for an i-supported result does not provide new support

[so...@googlecode.com]

Status: Accepted
Owner: maz...@gmail.com
Labels: Type-Defect Priority-Medium

New issue 159 by maz...@gmail.com: Identical justification for an
i-supported result does not provide new support
http://code.google.com/p/soar/issues/detail?id=159

When an identical justification already exists for an i-supported result,
Soar does not create the second justification nor does it associate the new
result with the original justification, which is necessary for it to
persist past the existence of the support it receives in the substate, so
the result is remove prematurely. (It's also possible that the existence of
the previous justification short-circuits asserting the preferences for the
new result entirely.)

What steps will reproduce the problem?

1. A rules fires in a substate producing a wme on the superstate, which
creates a justification that provides i-support.
2. An o-supported rule later fires, removing that wme.
3. A substate produces the exact same wme in the same way, i.e. it produces
the same justification.
4. A new wme is created but loses support when the support from the
substate goes away (such as when the substate terminates), it isn't linked
to a justification.

What is the expected output? What do you see instead?

Expect to see WME retain support when substate is removed.

Proposed Solution:

If no preference for that wme is being generated by the second firing at
all, we need to stop whatever is short-circuiting the addition of the new
preference. If it is being generated, then we just need to do (2)
Link the preference generated by the new firing to the previous
justification.

Another solution would be to just clean up the original justification when
we remove the WME that it supports, but it may be possible that the
justification may still be needed for other results it supports? [John:
This might work, but I think the relinking is safer.]


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