The definition of the systems engineering value stream is based on modelling the information flow. Information flow models are beneficial for performing systems engineering management efficiently. The benefits of unidirectional information flow models may give the impression that systems engineering as its best is a deductive process with the stakeholder requirements leading to unique and unambiguous solutions. However, human communication and natural laws feature mutual dependencies that become evident in systems engineering especially when system interfaces and process interfaces are considered. This paper amends two previous papers on the systems engineering value stream by system interface engineering considerations. Starting with clarifying the scope of system interface engineering, the paper proposes a precise terminology and defines the additional system interface engineering activities integrated into the systems engineering value stream.