Bovy, Rix, Foreman-Mackey and I gathered in the "vdB lounge" of the MPIA to discuss a graphical model for stars in the Milky Way disk, in part to guide our thinking about projects and in part to make a possible illustration for a review that Bovy and Rix are writing. There was some argument about where to put the extinction, and what to consider the
observables, with Bovy and Rix making the case that since they are given (by observers) temperature and gravity, these should be seen as observables, and me arguing that since these are coming from medium-resolution spectra, the spectra should be seen as the observables. This difference doesn't matter much to the inference, but part of my prejudice comes from the idea that graphical models can be thought of as causal models. Therefore I want my graphical model to represent the causal structure of the problem where possible.
Along similar lines I discussed with Beth Biller (MPIA) her projects to do exoplanet direct imaging campaign simulations based on data-driven models of the exoplanet population. Here one of the interesting things is that non-detections can be just as constraining as detections, and she has a nice framework for making all that happen. This is strongly related to exoplanet population modeling under consideration by Foreman-Mackey and myself.