5. The Language Of Product Definition

The language used for product definition is of paramount importance as it is a key objective to minimise the degree to which the language is open to interpretation.

The product definition needs to be precise, free from speculation or unqualified objectives and options. The individual responsible for product definition must recognise that the purpose of the prose is to define a product, not to simply write about it in some abstract sense.

Any product definition should include, as part of its introductory material, an indication of how to interpret the text. It should be clear whether a statement is a requirement, an objective, a desirable feature, or an option.

The application of standard expressions within the product definition is desirable. This clarifies the intent and or impact of the written requirement on the product specification.

Guidelines

The following simple guideline will clarify the intent of the writer if followed rigorously.

Requirements

Use the terms "must", "shall" and "it is a requirement" to specify the requirements on the design of the product, e.g. "The product shall operate across the temperature range -10 degrees C to +40 degrees C".

Objectives

All objectives within a product definition should be specified using the terms "should" or "it is an objective". All such objectives should have an associated indication of the obligations on the product designer or other party under the objective.

Obligations

Obligations should be written in the form of requirements, e.g. "The product should continue to operate in temperatures in the range 40 degrees C to 50 degrees C. Product specifications and user documentation shall highlight and detail any condition under which the product may cease to operate within this range."

Desirable Features

All desirable features, those that are requested but negotiable in some way, should be written as if they are objectives.