A discontinuity exists between modeling and object-oriented programming languages. This discontinuity is a consequence of ambiguous notions in modeling languages and lack of corresponding notions in object-oriented programming languages. It hinders the transition between software implementation and design and hampers software maintenance. This discontinuity is particularly acute for binary class relationships, such as the association, aggregation, and composition relationships. We present a solution to bridge the discontinuity between implementation and design for the binary class relationships: We propose consensual definitions of the binary class relationships in terms of four properties (exclusivity, invocation site, lifetime, multiplicity). We describe algorithms to detect these properties in Java source code.