An execution unit comprising a runlet and execution environments and methods for using runlets. According to one aspect, abstract parameters comprising function arguments defined for child runlet functions may be bound to corresponding real variables in a parent runlet. As a result, when a function corresponding to a child runlet gets invoked, it uses the current values of the parent runlet variables as the function arguments. According to another aspect, each runlet execute in an execution context comprising an instance of variables and parameters declared by that runlet. A context manager, typically implemented by an application server, may be used to manage execution of the runlets so as to prevent anomalies, such as race conditions. According to another aspect, abstract parameters for a runlet may be bound to corresponding application parameters for an application.