Reducing the wrapping effect

When solving ODEs by interval methods, the main difficulty is reducing the wrapping effect. Various solutions have been put forward, all of which are applicable for narrow initial intervals or to particular classes of equations only. This paper describes an algorithm which, instead of intervals, uses a larger family of sets. The algorithm exhibits a very small wrapping effect and applies to any type of equation and initial region. For the time being it handles only two-dimensional equations.