Given a changefeed of the form:
stream.reduce(f).changes({includeInitial: <II>, includeStates: <IS>})Assume that for the given f, we know the following properties:
<f_BASE>the initial accumulator forf<f_APPLY>a function from the accumulator and an element in the input table to a new accumulator<f_UNAPPLY>the inverse of<f_APPLY>in the accumulator