Missing unit

IBM® Engineering Requirements Quality Assistant (RQA) message: This requirement has a value with a missing or unclear unit of measurement. Effective requirements are specific and measurable. Ensure that numbers and values include a unit of measurement, and that the same units of measurement are used consistently across all requirements.

Explanation

Omitting the unit for a measurement or its tolerance range is a common error. A requirement author might omit a unit from a requirement if it seems trivial or obvious, or when the unit can be inferred from a neighboring requirement. However, each requirement must be self-sufficient and include specific units for all measurements.

Example 1

  • The speed of the toy car in water should be 90.

To eliminate the missing unit issue, modify the requirement as follows:

  • The speed of the toy car in water should be 90 km/h.

Example 2

Similarly, consider these two related requirements:

  • The fuel pump shall have a maximum volume of 1 liter.
  • The fuel pump shall have a flow rate of 250 l/h.

From the first requirement, you can infer that the flow rate in the second requirement is also in liters. However, if the requirements are separated, as they might be in a tool repository, the second statement must be self-sufficient and specify a unit of measurement for the flow rate:

  • The fuel pump shall have a flow rate of 250 l/h.