My review of the proposed Interval Template Library follows. This is based only on studying the documentation, and previous discussion of the library on the Boost mailing list (e.g. http://lists.boost.org/Archives/boost/2009/03/149396.php ). Joachim has clearly put a lot of work into what is a substantial and well-documented library. Unfortunately, it seems to me that it is built on a weak foundation. One of the most well-known problems involving intervals is to determine which of a given set of intervals contains a particular point. How to store a set of intervals in such a way as to make this problem efficient has been extensively studied. If an "interval tree" (See e.g. Wikipedia: http://en.wikipedia.org/wiki/Interval_tree) is used, then the problem can be answered in logarithmic time and linear space. (More precisely: if there are N intervals in the container and M overlap the point of interest, finding them should take O(M + log N) time and the data structure should take O(N) space.) I was hoping to find that this library was an implementation of an interval tree. But it is not: it is built on top of normal standard-library containers. The implementation used can find the intervals that overlap a point in O(M + log N) time, but to do so it needs worst-case O(N^2) space and I think it needs O(N^2 log N) time to build that structure. Presumably this complexity is not an issue in Joachim's application. Unfortunately, library code will be used in many different applications including those where optimal complexity is required. For example, consider trying to store the lifespans of people in a genealogy program: recording a few thousand people living over a few hundred years would approach the worse-case space complexity and need megabytes of storage. Perhaps other reviewers will feel that there are sufficient applications where this library is suitable to justify its inclusion in Boost. My feeling is that since the interval tree data structure is so well known and its performance is so much better, we should not accept this library. Ideally it would be possible for Joachim to replace ITL's current standard containers with an interval tree implementation. Could an interval tree be implemented with an interval sufficiently similar to a std::set/map to make that possible, without losing the complexity benefits? Once again, I believe that apart from this weak foundation this looks like an excellent submission that is comprehensive and well-documented. Regards, Phil.