Abstract： Transport experiment and linear response, one of our most basic emprical practice, is computed using Kubo’s formula, a connection that has been established since Luttinger’s time. In this talk I want to share some on-going thoughts about whether there is a subtlety on top of our usual practice, when applied to dissipationless transport in gapless systems. In particular, I will discuss a possible subtlety in connecting the anomalous Hall response measured in transport experiment to the usual Kubo formula computation. The possible subtlety is related to how we should treat the quasiparticle electric dipole moment that emerges from interactions.