Each domain segues in a seamless fashion from one to the next whereas the stages (phases) are gated from each other by very specific, measured requirements, which must be attained and agreed to before advancing to the next stage.

The Product Engineering domain is the link between the user (market) and the product (production); it is concerned with maintaining conformance of the product under development to the user, regulatory and market requirements and to build in quality and reliability while achieving cost goals.

The marketing and product information discovered and derived within the Market Development/Product Conception domain provides the input to the Product Engineering domain. The output of the Product Engineering domain supports full production, distribution, and service of the product and customer.

It has been verified³ that there is a strong relationship between the quality and appropriateness of the process used during the development phases of a product and the likelihood of a fault being introduced and perhaps remaining undetected. Products involving software/firmware are especially prone to faulty development: "The vast majority of software problems are traceable to errors made during the design and development process."⁴

Even non-consumer-oriented industries such as the aerospace industry are keenly aware of such development phase faults: "An endeavor that isn't planned, at least to some extent, is very unlikely to succeed."⁵ Anecdotal evidence gathered over many years in the high-tech product development industry has also revealed the same pattern.

This lack of practical, up-front planning occurs quite often within product development groups, especially in start-ups and small companies, and to a lesser extent within established medium to large companies.