Accessio

Accessio is a concept from Ancient Roman property law that decided ownership of an object or work that is somehow related to another object or work; one thing is considered the principal, and the other is considered to be an accession or addition to it. In general the owner of the principal thing, whichever it is, became the owner of the accession also. Accessio was not a specific rule, instead it was a principle with a number of special cases that had their own particular guidelines for determination of ownership.