Business Architecture is a model, typically expressed as a set of states, events, and transitions, that describes how products/entities and business events work together to satisfy appropriate business functions. This applies both to "mainline" functions like capital markets activities and "support" functions like talent management, change management, and quality metrics/continuous improvement. A good business architecture will have:
There are a number of frameworks that purport to model and communicate Business Architecture, including Zachman and xBML, and a number of bespoke tools (e.g. ProVision) that can model business process and interaction. It is important to note, however, that these are only frameworks for organizing and communicating information. They add no specific value in terms of actually defining a real working business architecture to (for example) do follow-the-sun portfolio trading and regional close.