Today?s model-driven engineering tools focus on the au- tomatic transformation of software models and lack essen- tial support for interacting with developers. This paper presents some lessons learned from building a standard compliant platform for the visual development of interactive consistency maintenance software. Based on an established requirements engineering case study, the paper illustrates the need for developer interaction and the controlled toler- ance of inconsistencies. This motivates the role of traceabil- ity links in two dimensions: links between application mod- els allow one to maintain consistency incrementally and tol- erate inconsistencies in a controlled manner. In the other dimension, links between transformation models enable the refinement of declarative descriptions of consistency con- tracts into constructive transformations. Such transforma- tions can be generated automatically from the contracts but tend to be optimized subtly by a transformation expert.