Physical Requirements

Definition

An physical requirement is a user-oriented quality requirement that specifies a required physical characteristic.

Objectives

The typical objectives of an physical requirement are to:

• Ensure that the system or component has the necessary physical property.

Measurements

Physical requirements are typically specified in terms of the following measurements:

• Density (mass per volume)
• Dimensions (length, width, height, surface area, volume)
• Hardness
• Location (physical and geographical)
• Strength (compressive or strength)
• Weight / Mass

Examples

The following are typical examples of physical requirements:

• “The buoy shall have a maximum density not exceeding 0.9 gm / cm 3.”
• “The secure satellite phone shall not exceed 15 cm in any direction.”
• “The transmission tower shall be located within 10 meters of 40-57.76122 North 085-12.76155 West.”
• “The automated people mover roof shall have a minimum crush strength in excess of 500 pounds per square foot.”
• “The television shall not weigh more than 10 pounds.”

Guidelines

The following guidelines have been found to be useful when producing physical requirements:

• The scope of an physical requirement can be:
  • A system
  • A component
• Where practical, physical requirements shall be specified quantitatively with explicit units of measure (e.g., pounds per square inch, kilograms, qubic centimeters, etc.).