According to the definition in http://specify6.specifysoftware.org/SpecifySchema.html, an Accession is acquisition of specimens. And indeed, in the model, an Accession has a one-to-many relationship with CollectionObjects.
A Deaccession is a removal of specimens. In the data model however, a Deaccession has no relationship with CollectionObjects, just with Accessions. This causes a problem:

On 20 March 2001, I received 50 specimens from the McGill University Herbarium. I store this as an Accession, with an Accession Number and an Accession Date. The 50 specimens are stored as 50 CollectionObjects, with a link to this one accession.
On 20 March 2004, I give 3 specimens of that original Accession as a gift to the University of British Columbia Herbarium. I want to store that information as a Deaccession (since I no longer have them in my collection). But since Deaccessions are linked to Accessions, I can only deaccession all 50 specimen (the whole Accession) or none at all.

As far as I can see, Deaccessions in the current data model only work for one or more whole Accessions. Deaccessioning CollectionObjects that don't comprise an whole Accession is not possible. The only workaround would be to create one Accession for each CollectionObject, which nullifies the reason of having Accessions.

Any solutions / comments?