There are 8 pillars to Business Analysis. These pillars are used with the inquiry model to elaborate and elicit the business solution. There is a lot of cross-over between the pillars, but they support a solid business solution.
Scope Modeling - context diagram, functional decomposition
Process Modeling - process flow diagram, swim-lane, value stream
Interaction Modeling - system to system diagrams, API models, State diagram, activity diagrams, ETL (Extract Transform Load), Business Intelligence
Decision Modeling - Decision tree diagram, decision log, weighted ranking table, decision table, logical decision path. Multiple criteria path.
Data Model - data dictionary, glossary, logical data model, physical data model, Entity Data Relationship Diagram, Data Flow Diagrams
Business Rules - self-imposed constraints, external constraints by government or regulatory, you will find them in a data model, decision models, and process models
Technical Modeling - entity, class and object modeling, configuration modeling, nonfunctional or environmental requirements to the next level, security, platform models, unique system setups,
Interface Modeling - Prototyping, wireframing, report mockups, UX, storyboarding.
If you covered all of these 8 pillars thoroughly, that could potentially be over 5,000 details or requirements to answer a single question or requirement. The pillars allow you to see how a requirement would fit into your organization from many different perspectives. The better constructed and detailed the pillars are, the stronger the requirement.