We present a view on software systems, which emphasizes that a software system shapes the user’s conceptual model. Regarding a software developer as a user, we point out the existence of a gap between the model of programs represented by a software development system and the software developer’s conceptual model of programs. To minimize this gap, we motivate an extension of software development systems to support architectural abstractions, and we propose a two level model consisting of a program level and an extract level.