For me, the role of project management (PM) is intricately tied with that of business analysis.    The PM leads a team focused on achieving a specific outcome in a specified time frame.

The business analyst role is a key component of the project.  For a project to complete successfully the expected outcome must be crystal clear. Business analysis is about providing that clarity.

What are we doing?

A project can start with a high-level statement of the goal.  For example, build a house or host a wedding.  This statement of what we are doing only draws a loose boundary.

Houses can widely vary in size and quality and although not specifically part of the build, location matters a lot.  The same applies to a wedding.

In fact, most project goals start with a broad statement of intent.  Moving to a detailed level of specificity (the scope of the initiative) is always a key step in the project.

Filtering the Wheat from the Chaf

A wide variety of stakeholders can contribution information, ideas and desires toward advancing the objectives of the project and ultimately contributing to the overall goal.

The business analysis function is to gather, process, structure and present evidence and recommendations for the project scope.  The scope can be determined collaboratively by consensus with full buy-in.

This is the most efficient and streamlined approach to achieve the project goal, although figuring it out as you go along could work it just is not an optimal approach.