Google Docs lets you address particular comments to people. They&39're notified of comments by e-mail, and responses sent by e-mail appear in the discussion thread.

The ideas behind Google Wave, a real-time communication technology the Net giant ditched, are making something of a comeback as a collaboration tool in Google Docs and Gmail.

Google announced discussions in Google Docs today, a new ability to automate the communications part of collaborations. Google Docs already let multiple people edit a document at the same time and to append comments to a document, but the discussions feature advances those abilities.

For one thing, comments now can be hidden once they've been addressed, not just deleted, and they can be resurrected if necessary.

For another, comments are adorned with the commenter's photo, and they can be addressed to specific people. Such a comment automatically generates an e-mail to the person, who can open the document with a link in the e-mail. Simply replying to that e-mail will insert the response to the comment in the document itself.

Wave users will recognize some of its features in these changes. Wave was a hybrid of e-mail, instant messaging, and group chat rooms. Though it ultimately failed at Google, the idea of collaboration--with both store-and-forward and real-time communications--has a lot to recommend it.

"Now you can easily tell who made a comment and when--with timestamps and profile pictures--and you can keep track of the conversation with e-mail notifications and reply to comments directly from your e-mail," said Scott Johnston, Google's group product manager for Google Docs, in a blog post.

For details about how it all works, check the Google Docs blog post.

Google Docs discussions can notify collaborators of changes to documents.