Business Analysis Methods, Tips and Techniques
The scope and focus of business analysis work must align with the business goals, objectives and strategies of the organization. This helps to ensure that the future state model that is created aligns with where the business actually wants go. Put a different way, you don't want to build yesterday's system.
To achieve strategic alignment, the business analyst should adopt a "top down" analysis approach by clearly understanding the corporate vision and ensuring that the project goals and objectives are aligned with the business goals and objectives. The future state business model that is built must reflect the business processes, information needs and architectures that will be needed going forward.
The risk of adopting a 'bottom-up" approach to business analysis is that valuable time and money can be lost modeling archaic, convoluted and soon-to-be redundant business processes that are not wanted in the future state. The BA must design tomorrow's business systems; not yesterday's business systems.
On exception, however, the business analyst will need to do some "bottom-up" modeling. This is occasionally needed in areas of high complexity, where an intimate understanding of the current state business model is required.
The Zachman Framework, developed by John Zachman, provides a wonderful overview of the types of business models that are created at each level of abstraction and for each perspective. It it a useful framework that will help you understand the difference between "top down" and "bottom up" business analysis.