1. A method of rescinding ownership of a cache line in a computer system, comprising: constructing a table of caching agent representations, each caching agent representation being accompanied by a validity indicator; receiving a cache line sharing list, each entry of the cache line sharing list indicating the potential ownership of the cache line by one or more caching agent representations that correspond to an entry of the sharing list; and conveying a snoop packet to a caching agent when the logical conjunction of an entry of the cache line sharing list that corresponds to a caching agent representation and the accompanying validity indicator meets a predetermined Boolean condition.