Conceptual modelling of user interfaces and interaction: models should capture the essence of what user interfaces and interaction will be and should be compliant with a meta-model expressing its semantics ; abstract and concrete syntaxes could then be defined to express these semantics, typically through a User Interface Description Language (UIDL); stylistics study how such syntaxes could be graphically conveyed.
Step-wise and structured approach: a set of rules and general principles should guide the modelling approach in order to master all the steps required to achieve the full development life cycle.
Software tools: a software suite is expected to support the aforementioned step-wise approach in order to properly conduct the development life cycle. This presentation provides a retrospective view on model-based and model-driven engineering of user interfaces since its inception and sketches some prospective views to their future avenues.