I am quoting the following statement from Madhav S. Phadke’s book Quality Engineering using Robust Design

“The ideal quality a customer can receive is that every product delivers the target performance each time the product is used, under all intendent operating conditions, and throughout the product’s intended life, with no harmful side effects.”

Though one may be working on a sub-system or a small module; to assure Quality one needs to look at QA from multiple dimensions – System, Product and Unit dimensions.

Also, throughout the lifecycle, flow of key information such as stake holder priorities and requirements have to be smooth, transparent and timely.