An infrastructure that allows applications to run with specified versions of dependent assemblies, wherein each assembly may exist and run side-by-side on the system with other versions of the same assembly being used by other applications. An application provides a manifest to specify any desired assembly versions on which it is dependent. Similarly, each assembly may have an assembly manifest that specifies the versions of assemblies on which it is dependent. During an initialization phase, an activation context is created for the application, based on the manifests, to map version independent names to a particular assembly version maintained on the system. While the application is in a running phase, for any globally named object that the application wants created, the activation context is accessed to locate the application's or assembly's manifest-specified version. The manifests and activation context constructed therefrom thus isolate an application from assembly version changes.