This article links to a whitepaper: Damon Poole: “Stream-based architecture for SCM.
As far as I understood from the first reading, idea of streams is very straightforward and simple concept making “streams of development” a first-class object in AccuRev repository. Streams are very easily presented on UI level, making them easily understood for software developer and release manager. Branches, tags, and private workspaces could be superseded by various flavors of streams.
E.g. “Release 4.0” is a stream. “Release 4.0.1” is the child stream. Changes made in 4.0.1 could be “promoted” to 4.0. When we start the “5.0” line of development, it automatically gets everything that was promoted to 4.0, either from older version or from bug-fix version (4.0.x).
I understand that streams could be enormously useful if they actually do the merging well. Technically this is handled easily by modern standards. Something like this could be done (and may be is already done) in many GUI clients for most open source version control systems.
Second part of the whitepaper is dedicated to AccuRev TimeSafe, which is the underlying repository format. I have to remark that the article only compares TimeSafe features with CVS and ClearCase repository features. Those are embarrasingly easy targets for criticism. Why are modern repository formats such as Subversion FSFS and Git not mentioned? Are they technically superior? ;)
Article on Timesafe: Damon B. Poole “The Timesafe Property - A Formal Statement of Immutability in CM”.
See also: DaveOnSCM: “Agile: Branches vs. Streams”.