One of the key challenges in the design of a Safety-Critical Cyber-Physical Systems is Requirements Analysis. Current Requirements Analysis approaches range from informal, human-centered ones that are hard to automate, to formal approaches that often lack freedom of expression. Furthermore, most approaches are general-purpose and do not focus on a particular domain, which makes identifying the specific requirements of a given domain less trivial. To overcome these challenges, this paper presents aDSL, a Domain-Specific Language and toolset for Requirement Analysis of Safety-Critical Cyber-Physical Systems. The approach comprises a mixture of informal and formal elements to enable both automation and freedom of expression; a number of stakeholders introduce and negotiate about their requirements. The aDSL language is used to precisely, concisely and unambiguously describe all such requirements. We have validated aDSL, using simulation techniques and actors that represent the stakeholders, on a case in the agro-machines domain. The proposed approach allows the discovery of requirements in a semi-automatic way.