There are two big pictures that need to be understood for any business analysis engagement. The domain big picture and the deliverable big pictures.
The domain big picture is the overall understanding of the patterns, principles, and paradigms of the domain. This knowledge is required as it sets the stage for any decisions that take place. A decision without understanding the domain the decision fits into is a poor decision.
The second big picture is the deliverable big picture. What are the purpose and the outcome that the deliverable is to create? Blindly creating a deliverable without taking into account what the deliverable is trying to achieve results in a misalignment between work completed and what ultimately needs to be achieved.
Every deliverable has a different purpose. The quality of the deliverable is based on the quality of the outcome the deliverable creates. A good deliverable for defining scope is a deliverable that is effectively used to answer scope questions throughout the project. The form and the format is related to the outcome. If it is an agile project the scope deliverable can be light and point form. If it is a project with a third-party vendor, the deliverable would have to be concise legal type format.
Know the purpose in order to determine the form and the format of the deliverable.