The resources needed by an application to execute are declared by the application. When the application is activated, only the declared resources are made available to the application because only the declared resources are connected to the execution environment. Accessibility to resources may be controlled by the operating system by making the resource visible or invisible to the executing software by mapping a local name used by the executing software to a global resource, possibly limiting the type of access allowed. Because the executing software relies on the mapping function performed by the operating system for access to resources, and the operating system only maps names declared by the software, the operating system can isolate the software, and prevent the application from accessing undeclared global resources.