The task and data abstraction level addresses the why and what questions, and the idiom level addresses the question of how. Each of these levels has different threats to validity, so it is a good idea to choose validation method with these levels in mind. At the top is the situation level, where consider the details of a particular application domain for vis. Next is the whatwhy abstraction level, where map those domain-specific problems and data into forms that are independent of the domain. The term domain is frequently used in the vis literature to mean a particular field of interest of the target users of a vis tool, for example microbiology or high-energy physics or e-commerce. Each domain usually has its own vocabulary for describing its data and problems, and there is usually some existing workflow of how the data is used to solve their problems.