A process'es view of its execution environment is determined by the semantics of the available system calls; change the behavior of the system calls and one changes the process'es view of its environment. Operating systems typically implement the abstraction of a single view shared by all running processes. For example, all processes in a given system share the same view of the file system; the same pathname refers to the same file, mounting and unmounting remote or removable file systems have global effects.
There are a few notable exceptions; system calls whose purpose is to solve problems related to having a solitary inflexible view of the environment. (e.g. chroot which is used for enforcing secure access to the file system.) View-OS is an approach for extending an existing OS via an abstract OS layer, which by applying a kind of polymorphism to process views, generalizes the chroot approach: the behavior of a system call can be defined on a process (group) by process (group) basis. Therefore, each process in View-OS has its own view of the execution environment, i.e. its own view on networking, file systems, existing devices, inter-process communication, etc. Furthermore, process view redefinition in View-OS can be selectively applied to only specific portions of a process'es ``default'' view: e.g. a process can change its view on the file system, or the networking service or even only on a subtree of the file system
