Complementary practices provide a basis for better understanding your process. The trick to complementary activities is that you don't do them in lock step or in isolation. They work together to produce better results in combination. The value proposition is that they produce more value together than they do separately. The goal of software development is to produce a system that meets customer requirements. Process provides value when it helps you do this more efficiently and with less risk. Complementary activities can help you understand the reasons for following the process. The key factor to remember is that the right process is the one that lets you deliver better software, faster.