1. A physical storage device having stored thereon a representation of a continuation-based runtime activity that includes: an environmental logic portion that is structured to assign each of plurality of values to a corresponding parameter of a plurality of parameters at execution time of the continuation-based runtime activity; and a callback invocation portion that is structured to invoke one or more activity callbacks that 1) are available for use with the continuation-based runtime activity and that 2) each have one or more characteristics that are used to identify the one or more activity callbacks, wherein the callback invocation portion is structured to cause the following to be performed at execution time of the continuation-based runtime activity for each activity callback that is available at execution time and that has the one or more characteristics: an act of instantiating the activity callback; an act of providing the plurality of values from plurality of parameters specifically to the instantiated activity callback, the plurality of values being provided in a particular order while refraining from specifying which parameter each provided value is assigned to; and an act of executing the instantiated activity callback, such that the instantiated callback may operate using the provided plurality of values, the instantiated activity callback being configured to identify which of the plurality of parameters each provided value is assigned to, based on the particular order in which the plurality of values were provided.