The main concern of the software industry is to deliver more products in shorter time-cycles to customers with an acceptable economic justification. In virtue of these concerns, the software industry and researchers in the field of software engineering have engaged in the process of adopting lean principles. In this paper, we are seeking the knowledge that could help us better understand the nature of flows in software development. We define a generalized concept of the value creation points and an axiomatic system that capture the specifics of software development. Further, a generalized definition of the flow makes it possible to identify super-classes of waste sources. Finally, we define a concept of decision flow, suggesting what a value creation point could be in the software development context. The decision flow is an inseparable part of the software development activities and it carries capabilities of adding or diminishing the value of products.