Requirements' fields:

• Product requirements: properties of a system or product
• Process requirements: activities performed by an organization

Types of requirements:

• Architectural requirements: architectural structure and behavior
• Business requirement: goals, objectives, needs
• User requirements: intended interaction
• Functional requirement: capabilities, behavior
• Quality-of-service requirement: reliability, testability, maintainability, availability etc.
• Implementation (transition) requirement: role changes, education, migration
• Regulatory requirement: laws, contracts, policies

Requirements' characteristics:

• Unitary/cohesive
• Complete
• Consistent
• Non-conjugated (atomic)
• Traceable
• Current
• Unambiguous
• Specified importance
• Verifiable