  Many systems nowadays require protection against security or safety threats.
A physical protection system (PPS) integrates people, procedures, and equipment
to protect assets or facilities. PPSs have targeted various systems, including
airports, rail transport, highways, hospitals, bridges, the electricity grid,
dams, power plants, seaports, oil refineries, and water systems. Hence, PPSs
are characterized by a broad set of features, from which part is common, while
other features are variant and depend on the particular system to be developed.
The notion of PPS has been broadly addressed in the literature, and even
domain-specific PPS development methods have been proposed. However, the common
and variant features are fragmented across many studies. This situation
seriously impedes the identification of the required features and likewise the
guidance of the systems engineering process of PPSs. To enhance the
understanding and support the guidance of the development of PPS, in this
paper, we provide a feature-driven survey of PPSs. The approach applies a
systematic domain analysis process based on the state-of-the-art of PPSs. It
presents a family feature model that defines the common and variant features
and herewith the configuration space of PPSs
