  Resolved observations are bringing new constraints on the origin of radial
gaps in protoplanetary disks. The kinematics, sampled in detail in one
case-study, are indicative of non-Keplerian flows, corresponding to warped
structures and accretion which may both play a role in the development of
cavities. Disk asymmetries seen in the radio continuum are being interpreted in
the context of dust segregation via aerodynamic trapping. We summarise recent
observational progress, and also describe prospects for improvements in the
near term.
