Use cases and users’ stories being the two major approaches to requirements, outlining their respective scope and purpose should put projects on a sound basis.

To that end requirements should be neatly classified with regard to scope (enterprise or system) and level (architectures or processes).
- Users stories are set at enterprise level independently of the part played by supporting systems.
- Use cases cut across users stories and consider only the part played by supporting systems.
- Business stories put users stories (and therefore processes) into the broader perspective of business models.
- Business cases put use cases (and therefore applications) into the broader perspective of systems capabilities.
Position on that simple grid should the be used to identify stakeholders and pick between an engineering model, agile or phased.
FURTHER READING
- Focus: Use Cases & Users Stories
- The Scope of Agile Principles
- Thinking about Practices
- Use Cases & Action Semantics
- Business Processes & Use Cases
- Business Stories: Stakeholders’ Plots & Users’ Narratives
- Use Cases are Agile Tools
- Agile & Models
- Focus: Business Processes & Abstraction
- Abstractions & Emerging Architectures
- Focus: Business Cases for Use Cases
- Projects as non-zero sum games
- How to pick development models