As part of our municipal work here at Sunlight, we're inviting various people to share their take on what makes a city and why transparency at this level is important. Today's post is from Cate Long, a guest contributor to Reuters.com on the municipal bond market.  By Cate Long Alisha Green of Sunlight Foundation is working on a project to identify the ways that different types of data are used to describe cities. She put up a great post that sketches out a number of ways to view a city demographically, including population density, unemployment and housing. She asked me recently to write about how I personally view cities. I think of cities almost entirely as cash flow machines that collect taxes and provide social services. That is muniland. Here are Alisha’s questions and my answers: 1. From your point of view, what is a city? Cities are legal entities that are incorporated to provide essential services; especially police, fire, education and water and sewer systems. Depending on the state, cities have legal authority to enter contracts, collect specific types of taxes and maintain judicial systems. Many cities also provide more expansive social services including care of the elderly and disabled and maintenance of parks and hospitals.