Data revealing lots of facets about cities are becoming increasingly available, which provides an unprecedented opportunity to get and understand a whole picture of how cities work. In this paper, we first give a brief introduction to the study of data-driven smarter cities (D2SC); second, we introduce and classify some common data available about cities; third, we present four main research objects and features in D2SC, and survey the common research issues dealing with each object; finally, we propose a generic framework and discuss the research challenges