Ideal Population
The ideal population is the maximum population that a product could possibly target under ideal conditions.
Under ideal conditions, if standard engineering design practice is adopted, each new product will first be defined by a specification or set of requirements, before any product concepts are developed. Those users who could use an idealised product (i.e. one that is unconstrained by the technical limits and trade-offs that affect any real, tangible product) based on those requirements can be thought of as the 'requirements' population.
However, this definition is problematic because it is hard to define a particular stage of the product design cycle where the requirements are fixed and do not alter, short of the final product itself.
Consequently, explicit definitions of a requirements population are very difficult to specify. However, the concept of capturing something other than the included population is important. Therefore, we need to specify a population where it is acknowledged that the population will change, based on how the requirements develop and evolve. This is referred to as the negotiable maximum population.