Deriving full repetition in Blackfoot with additive focus

I argue that Blackfoot’s method of marking repetition, mattsista’- consists of two morphemes, matt- and ista’-. While both encode an additional event, matt-’s event is restricted only to being a focus alternative to the asserted event, leaving predicate identity and temporal precedence to be encoded by ista’-. I propose that ista’-’s event variable requires a linguistically encoded antecedent which matt-’s event acts as, deriving the fact that mattsista’- has a focus-sensitive interpretation.