The users of management information systems and the designers and programmers of such systems live in different worlds; they have different backgrounds, skills and motivations. As a result communication between the two groups can be difficult. Communication can be improved by formulating explicit formal models of the data of interest. Implicit data models are in any case pervasive and unavoidable. A fixed length sequential file with a certain record layout is already a crude and very restrictive model of the underlying data. More flexible and sophisticated models imply a more abstract view of data. In its simplest form this merely requires separation between physical and logical data structure. In its most advanced form this leads to the concept of a relational data-base. Other forms of data-bases are somewhere between these two extremes. It is argued that the traditional communication path "user to analyst to programmer" impedes communication. More modern organizational structures, such as the chief-programmer-team can be more effective. Fictitious and real examples are used to illustrate the concepts described above.