Design rationale is supported by QOC (Questions, Options, and Criteria), a graphical semi-formal notation that highlights the key questions in a design and links them with possible options and criteria supporting those options. The design rationale editor allows several users to build a QOC rationale by creating nodes (Questions, Options or Criteria) and connecting them together. Users can modify nodes in mutual exclusion, note their actions in a shared log, and hide or view certain nodes to make browsing easier.

The system is designed using an iterative development method with several stages. The first stage is requirements elicitation, which relies here on previous observational studies on design rationale. Next, the high-level task analysis stage is performed using the ConcurTaskTree notation, which combines a graphical tree-like representation with LOTOS composition operators. The next two stages, detailed interaction and prototyping, are carried out using UAN (User Action Notation) and the Clock language, respectively.

The final stage in the development, namely establishing task conformance properties, is performed by means of formal verification. To achieve this, the Clock implementation of the system is translated into an interactor network described in LOTOS and the EVALUATOR tool of CADP is used to check the locking properties previously established during the task analysis.