A system comprising a computing device implementing a virtual machine which uses classloaders to load class files and create class objects for running applications, said computing device providing multiple execution environments, wherein an environment comprises a configuration combined with a set of higher level APIs, and a configuration comprises a virtual machine and a minimal set of class libraries; wherein the execution environments provided by said computing device comprise an alpha environment configured to have an alpha capability in the form of one or more resources available to the alpha environment and a beta environment configured to have an associated beta capability in the form of one or more resources available to the environment, wherein the alpha environment is configured to be isolated from the beta environment, and wherein the alpha capability has a greater capability in that it provides a broader set of resources than the beta capability, said system further comprising an alpha software application and an alpha environment class-loader associated with the alpha environment , and a beta application , a beta environment application class-loader , and a beta environment class-library implementation class-loader associated with the beta environment ; wherein the alpha software application associated with the alpha environment is configured to be processed on the alpha environment such that the alpha software application is denied direct access to the beta environment and the beta software application associated with the beta environment is configured to be processed on the associated beta environment such that the beta software application is denied direct access for the alpha environment; and wherein a request issued by the beta environment application to the beta environment may access the alpha environment via the beta environment class-library implementation class-loader . wherein the execution environments provided by said computing device comprise an alpha environment configured to have an alpha capability in the form of one or more resources available to the alpha environment and a beta environment configured to have an associated beta capability in the form of one or more resources available to the environment, wherein the alpha environment is configured to be isolated from the beta environment, and wherein the alpha capability has a greater capability in that it provides a broader set of resources than the beta capability, said system further comprising an alpha software application and an alpha environment class-loader associated with the alpha environment , and a beta application , a beta environment application class-loader , and a beta environment class-library implementation class-loader associated with the beta environment ; wherein the alpha software application associated with the alpha environment is configured to be processed on the alpha environment such that the alpha software application is denied direct access to the beta environment and the beta software application associated with the beta environment is configured to be processed on the associated beta environment such that the beta software application is denied direct access for the alpha environment; and wherein a request issued by the beta environment application to the beta environment may access the alpha environment via the beta environment class-library implementation class-loader . <EOS>