Hardware Constraints

Definition

A hardware constraint is a constraint that constrains the architecture, design, or implementation of a hardware component.

Objectives

The typical objectives of a hardware constraint are to:

• Ensure that some or all hardware components conform to necessary architecture, design, or implementation constraints imposed for business or technical reasons.
• Ensure that the hardware components have required characteristics such as:
  • Required vendor.
  • Required product model.
  • Physical size.
  • Physical weight.
  • Power requirements (e.g., voltage, wattage).
  • Resistence to (tolerance of):
    • Accelleration (e.g., dropping on a hard floor from a given height).
    • Electric shock tolerance.
    • Humidity levels.
    • Pressure (air or water) ranges.
    • Radiation hardening (e.g., electromagnetic pulse, beta and gamma radiation levels).
    • Temperature ranges.
    • Vibration tolerance.
    • Water exposure.

Examples

The following are typical examples of hardware constraints:

• “The application shall only use server computers from Sun Microsystems Incorporated.”
• “The application shall only portable barcode readers weighing less than 8 oz.”
• “No portable hardware component shall weigh more than 20 kilograms.”
• “The application shall only use commercial-off-the-shelf (COTS) hardware components.”
• “When broken down for transport, the entire set of hardware components of the application shall be transportable within the cargo hold of a single C131 military transport airplane.”

Guidelines

The following guidelines have been found to be useful when producing hardware constraints:

• Do not unnecessarily constrain the architecture, design, or implementation of hardware components.
• Avoid overlap with usability requirements (involving physical transportability).