Hi All, I've been working on some extensions to allow users to add annotations to tree data structures (explanation of the idea here: http://je4d.blogspot.co.uk/2013/01/boostintrusive-annotated-trees-part-1.htm...). This isn't a new library submission, but it's a fairly substantial modification to Boost.Intrusive, so I've got the following questions on my mind: 1. Is there interest in having such functionality in boost? 2. If so, should the changes go through the formal review process? Regarding the level of interest: To the best of my knowledge, no one has yet released a library that provides this functionality. I have, however, come across a few things that indicate that the technique is in use: http://is.gd/PA1Lhm (Evidence of demand for such a library) http://is.gd/Lepzrq (A binary tree with a 'pixel height' annotation) http://is.gd/PMb6Fy (A node-count annotation on B-trees) http://is.gd/RHjpeQ (Paper about a "count" annotation on suffix trees) http://is.gd/lHVhC0 (About the usefulness of annotations. Separates the data from annotations, unlike the proposed library) Many thanks, Jeff Snyder (aka je4d)