In this paper we present a generalised framework for expressing batching strategies of a mix. First, we note that existing
mixes can be represented as functions from the number of messages in the mix to the fraction of messages to be flushed.
We then show how to express existing mixes in the framework, and then suggest other mixes which arise out of that framework.
We note that these cannot be expressed as pool mixes. In particular, we call binomial mix a timed pool mix that tosses coins and uses a probability function that depends on the number of messages inside the mix
at the time of flushing. We discuss the properties of this mix.