Putting Architectures into Perspective
The diagram below represents some ideas on resolving the meaning of different architectures.
Enterprise Architecture is repositioned to be truly the architecture of the enterprise. Enterprise Architecture as currently typically practiced is renamed Enterprise IT Architecture. Business Architecture is effectively the ‘high-level’ architecture of the entire enterprise. A layer is shown that represents the bridge between the ‘high-level’ business architecture and specialised architectures, which essentially refine the detail. I’ve taken the liberty of assuming that specialist architectures other than IT would make sense, although this idea needs a lot more development.
The model of architecture scope represented here is similar to the widely accepted NIST Enterprise Architecture model (National Institute of Standards and Technology, 1989) as depicted below. I have inverted the pyramid from the original NIST model to emphasise the relative scope of business architecture versus Enterprise IT Architecture, referred to as Information Systems Architecture in the NIST model.
As a further observation, these days it seems that the NIST concept of Information Architecture has rather fallen through the cracks in most organisations. Information architecture is less about content and document management, more about communications and command and control within a business and is effectively its nervous system. Such systems of information have always been required irrespective of any technology and somebody needs to design them. They are effectively the bridge between business architecture and information technology and in that respect the NIST model is still very relevant but this aspect isn't well understood, and certainly not well practised.