The house of quality, a part of QFD, is the basic design tool of quality function deployment. It identifies and classifies customer desires (What's), identifies the importance of those desires, identifies engineering characteristics which may be relevant to those desires (How's), correlates the two, allows for verification of those correlations, and then assigns objectives and priorities for the system requirements. This process can be applied at any system composition level (e.g. system, subsystem, or component) in the design of a product, and can allow for assessment of different abstractions of a system. It is intensely progressed through a number of hierarchical levels of What’s and How’s and analyse each stage of product growth (service enhancement), and production (service delivery).