I see business architecture covering business capabilities, business processes, functions and organisational design. In the past my senior executive (the Board and the Executive Committee) have identified the operating model they want to move to and the goals, objectives and strategies that they believe will get them to it and by when. Our business architecture then described what capabilities the organisation would need, the functions that would need to be in place, the processes that would have to be executed and the efficient organisational structure to drive them.
These would be supported by governance, principles and standards to provide a framework for change.
This drives the technology areas who need to remain aligned to the business architecture - of course this works in both directions.
Are there any other areas you use in your business architecture?