The EE organisational design theory or BETA theory is a theory about the development of a system, called the object system (OS), which is going to support another system, called the using system (US). The US uses the services that are (going to be) offered by the OS. The development process is conceived as the sequence of function design, construction design and implementation design, where the notion of design corresponds fully with its definition in Chap. 3 . Although the BETA theory is generally applicable, we apply it specifically to the development of O-organisations and enterprise information systems (EISs), which comprise parts of an enterprise’s I-, D- and M-organisation as defined by the ALPHA theory. Both Enterprise Ontology and Enterprise Architecture are crucial notions in the General System Development Process (GSDP), which is the general development model. Function design starts from the ontological model of the US, and construction design ends up in the ontological model of the OS. The notion of architecture appears to be ambiguous in current theory and practice. In Enterprise Engineering, it is exclusively used in its meaning of guidelines (principles, standards) that are applied in the system development process. These guidelines apply to a class of systems, in contrast to user requirements, which apply to a particular system. Consequently, the applied architecture in a development process is a source of both functional and constructional requirements, in addition to the functional and constructional requirements that are provided by the future users of the OS. In order to manage the, usually large, set of user and architectural requirements, GRAF (General Requirements and Architecture Framework) is presented.