EARS is a technique used by Rolls-Royce and many other organizations around the world to capture requirements in natural language in a precise manner. In this paper we describe the EARS-CTRL tool for writing and analyzing EARS requirements for controllers. We provide two levels of analysis of requirements written in EARS-CTRL: firstly our editor uses projectional editing as well as typing (based on a glossary of controller terms) to ensure as far as possible well-formedness by construction of

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... e requirements; secondly we have used a controller synthesis tool to check whether a set of EARS-CTRL requirements is realizable as an actual controller. In the positive case, the tool synthesizes and displays the controller as a synchronous dataflow diagram. This information can be used to examine the specified behavior and to iteratively correct, improve or complete a set of EARS-CTRL requirements.