Most projects are initiated to accomplish a specific objective that ties back to one or more business goal(s). In order for the project to meet the business objectives, it's critical that the requirements also be aligned to the business goals.
A good business analyst makes sure
they clearly understand the project objectives and business goals the project is intended to support. If a business goal includes maximizing the efficiency of operational processes, for example, the analyst will try to ensure that the processes in the project are as efficient as possible, with few unnecessary hand-offs and no redundancies.
Similarly, clearly understanding the business goals and project objectives at the start will make it easier to evaluate and prioritize the requirements according to how well they support the objective. Knowing the goals and objectives will also make it much easier to manage the inevitable changing requirements.
For example, if two requirements compete for resources, and one better supports the business goal, it will obviously have higher priority.
Understanding the business goals will also help you identify the high-level business requirements. Often called "vision requirements," these are top-level requirements that emerge first, and to which all the other requirements must be subordinated in order to deliver a cohesive solution.
For example, imagine that the business goal is "Increase sales volume in new sales, cross-sells, and up-sells." The high-level business requirement for a specific project might be "Increase cross-sells through the use of targeted marketing and voice response tools." The specific requirements at the detailed level of technology and users will tie back to these business goals. At this fine-grained level, the business rules and nonfunctional requirements might include "Customers with five or more purchases on record have highest call priority," or "Cross-sell messages shall not exceed 45 seconds." Every requirement must support the highest-level business vision requirements that guide the project toward meeting the business goals.