Defining sukkot - if you put schach on top of an alleyway, you can ha e a kosher sukkah - reviewing many cases, in ways that are reminiscent of Eruvin. Also, the need for more shade than sunlight for the sukkah to be kosher. And that shade needs to be coming from the roof (the schach), and not via cracks or gaps in the walls. Plus what is essential to a sukkah? There are ways that a sukkah is similar to a permanent structure. And other ways that it's clearly temporary. A list of sages each has a detail to contribute to these characterization.