'<h2 class=abstract> At the edge of Design by Contract </h2> <p class=abstract>Combining the Hoare-Dijkstra concepts of assertions and systematic software construction with principles of object technology and data abstraction, Design by Contract provides a solid basis for building, testing, documenting and maintaining quality O-O software. This presentation will examine issues at the forefront of Design by Contract, including a number of problems to which no answer is known at the moment, covering in particular the areas of program correctness, component validation, and concurrency.'