Yet another way to integrate message- and artifact-based collaboration is to link private messages and public artifacts. Some mail systems link artifacts to messages in that they understand artifact names (such as URLs) in messages and allow users to click on them to launch artifact viewers. Conversely, as we saw in Quilt, messages about an artifact can be linked directly to the artifact. Moreover, in Quilt, messages about a user's activities on an artifact (such as ''Reorganized section 2'') can be automatically mailed by the system to collaborators who have expressed an interest in them.