Frameworks and Methods
The different types of data model (and metadata model) are best viewed within the context of a governing framework – they all form part of an Enterprise’s view of its ‘architecture’ (using the term very loosely here), and are generally viewed as distinct layers within the ‘data’ stream of an architecture. For example, the Zachman Enterprise Architecture framework (see www.zachmaninternational.com) identifies 4 separate levels of data model – the Scope (contextual), Business (conceptual), System (logical), and Technology (physical) models. This framework is supported by several of the Enterprise Architecture tools on the market, with varying degrees of compliance. There are also a variety of development methodologies, such as Merise and Information Engineering, that have their own view.
Many practitioners of data modelling use a pyramid to illustrate the different types of model that can be produced, and I make no apologies for doing the same. This particular shape is well suited to the task for two reasons:
- it supports the principles of ‘layers’ (you’ll see what I mean below)
- as we move down the layers, everything grows – the number of models, their complexity, and the number of objects included
The pyramid consists of four tiers, providing increasing detail as you move towards the base.