Adding chunks to declarative memory in productions

[asmaloney]

(Disclaimer: I'm trying to understand not only the concepts but the 3 implementations at the same time, so please correct any misinterpretations!)

In pyactr and vanilla, (some?) buffers have the concept of harvesting which I think means that when the buffer is cleared, the contents are added to the memory associated with the buffer (if any)?

The clearest indication is in pyactr's Goal-derived buffers (e.g. goal & imaginal) which has a clear method (goals.py):

    def clear(self, time=0, harvest=None):
        """
        Clear buffer, add the cleared chunk into decl. memory. Decl. memory is either specified as default_harvest, when Goal is initialized, or it can be specified as harvest here.
        """
        if harvest != None:
            if self._data:
                harvest.add(self._data.pop(), time)
        else:
            if self._data:
                self.dm.add(self._data.pop(), time)

This seems to be the way to add chunks to declarative memory from within a production.

The ACT-R reference is a bit confusing w.r.t. harvesting and moving chunks into dm, but it says:

By default all buffers are subjected to the strict harvesting practice, but buffers can be exempted from that by specifying them with the :do-not-harvest parameter. (pg.219)

ccm doesn't seem to have any mechanism for doing this - neither the Buffer nor the ImaginalModule clear() methods reference any of this. I think to add chunks to declarative memory, you must do it explicitly by calling dm.add() within the production? I don't think the others allow this direct manipulation.

Can anyone help clarify this?

[asmaloney]

Definition of "strict harvesting" from the ACT-R manual:

Strict harvesting means that when a production tests a buffer on its LHS (harvests the chunk) it will automatically clear that buffer in the actions of the production. That will occur unless either: a modification is performed on that buffer (either a buffer modification with an = or a modification request with a *) or the buffer has been specified as one which should not be strict harvested using the :do-not-harvest parameter. (pg. 240)

[asmaloney]

From the video An Analysis and Comparison of ACT-R and Soar by John Laird:

Add chunk to DM when any buffer is cleared

This lines up with my initial understanding and makes it more surprising that ccm doesn't seem to do this.