Requirements represent obligations and responsibilities to perform between two or more entities.  These agreements are usually about the form, fit and function of the system.  Requirements implies that relationships must be satisfied for a system to perform.

Requirements specifications are complete when two or more entities (software, hardware, people, services) agree to perform satisfactorily to enable the system to perform better than the individual entities, alone.\

Refinement or decomposition of requirements are further explanations that these obligations are understood and can be performed, leading to confidence in the entities involved in the system.

• Systems Requirements:
  Performance
  Weight
  Volume
  Energy Balance
  Momentum Balance
  Mass Balance
  Functional
  Environmental
  Lifetime
  Maintenance
  Operability
  Reliability
  Availability
  Safety
  
• Element and Subsystem Specifications:
  Performance
  Weight
  Volume
  Temperature
  Pressure (Pressure Drop)
  Flowrate
  
• Component and Part Specification:
  Performance
  Weight
  Volume
  Catalog Number
  Color
  Size
  Length
  Material
  Cleanliness
  
  

10/21/2007 last update
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