MODAF Concepts
How do MODAF layers interrelate?
It is helpful to think of the MODAF Strategic, Operational and System Views as providing a layered architecture framework. This is illustrated below.
Each ‘layer’ is shown in the picture together with some of the key data objects that need to be addressed to create a MODAF architecture.
The strategic viewpoint represents the capability and business context at the enterprise level. The operational viewpoint represents capability within an operational setting – operational views have a capability and temporal context set by the strategic views. The system viewpoint represents capability at the level of solution specification.
Taken together, these layers can be viewed as representing three different levels of abstraction. The idea of abstraction (i.e. generalising so as to move away from specific examples) is key to correct application of model-driven development.
Within a layer or viewpoint, the key data objects shown in the figure above are related to each other. They are ‘key’ in the sense that the primary views can be constructed by correctly modelling these data objects and their relationships. The semantic and syntactic definition of the data objects, and the allowed relationships within a layer, are provided in the MODAF Meta-Model.
The key data objects in one layer are related to those in the layers above and below. Some of these connections are illustrated below.
Considering the System and Operational Viewpoints, the more obvious connections are between Data/Information and between Function/Activity. The Resource/Node connection is perhaps less obvious but, in fact, Resources (systems, people, organisations) play a very similar role – as the focus for structural modelling – in the System Viewpoint as Nodes do in the Operational Viewpoint.
The placement of organisations in MODAF is difficult. Organisational structures may be seen as strategic (e.g. in enterprise re-structuring, mergers, etc.). They may be seen as operational (e.g. process owners). Or, they may be seen as part of the solution (e.g. ORBATs, force structure, etc.). MODAF models organisations in three main views – OV-4, SV-1 and AcV-1. The connection is that, in practice, an Enterprise only has one set of human resources. Indeed it is perfectly possible for the same individual post holder both to be a process owner and at the same time to be a system operator. See the article on Background and Introduction to Defence Lines of Development for more information.
Understanding and making use of these vertical connections is essential to achieving the benefits of Enterprise Architecture. One of the architectural principles underpinning MODAF is that elements within a Viewpoint are strongly coupled whereas elements between Viewpoints are more loosely coupled.
Page version 1.1, dated 4th April 2007