A general graphic model for organizational information systems (IS) is proposed. The model includes generalized decision making and data manipulation functions to regulate generalized organizational processes through flows of information. The general IS model serves as a basic pattern to approach the design of any IS. In particular, alternative IS strudures or designs can be derived from the model. Structures include not only information that will be computerized but also the prescription of the decision making behavior of the information users. The existence of alternatives leads to a problem of evaluation for which a quantitative modeling approach is proposed.