I am reading Patterson's paper *[Knowledge representation in bicategories of relations](https://arxiv.org/abs/1706.00526)*.  It looks like it has many of the properties of the Markov categories which Fritz has been detailing in _[A synthetic approach to Markov kernels, conditional independence and theorems on sufficient statistics](https://arxiv.org/abs/1908.07021)_.  Is the bicategory of sets and relations actually a Markov category?