  Component-based development is one of the core principles behind modern
software engineering practices. Understanding of causal relationships between
components of a software system can yield significant benefits to developers.
Yet modern software design approaches make it difficult to track and discover
such relationships at system scale, which leads to growing intellectual debt.
In this paper we consider an alternative approach to software design,
flow-based programming (FBP), and draw the attention of the community to the
connection between dataflow graphs produced by FBP and structural causal
models. With expository examples we show how this connection can be leveraged
to improve day-to-day tasks in software projects, including fault localisation,
business analysis and experimentation.
