Small Problem 6 of DARPA PPAML Challenge Problem 4, the “Network Analysis Expressiveness Challenge”: write a generative model of an undirected graph in which nodes arrive sequentially and attach their edges via a mixture of uniform and preferential (“rich-get-richer”) attachment, then condition on global graph properties such as the clustering coefficient or the degree distribution to infer the posterior over the attachment mixture weight and the new-edges prior. The original Galois repository (GaloisInc/ppaml-cp4) is no longer available, but the problem spec survives: