In the early 1990s, Alistair Cockburn began working on methodologies at IBM. Mr. Cockburn's approach was to take some of his own experience and marry that with the experiences of other project managers who had tried (or were in the process of trying) to improve development processes. The result is not a single methodology but rather a family of methodologies to accommodate different project types and complexities. The Crystal family of methodologies is designed with the view that most people do not work as well with highly disciplined methodologies such as XP. So although Crystal methodologies are heavily oriented toward people and communicating (just like XP), they are not as productive; Cockburn opted to trade off productivity for ease of use.
The key element of the Crystal family is that the methodologies are iterative and designed to help people find and correct mistakes early.