Data validation rules constitute the constraints that data input and processing must adhere to in addition to the structural constraints imposed by a data model. Web modeling tools do not make all types of data validation explicit in their models, hampering full code generation and model expressivity. Web application frameworks do not offer a consistent interface for data validation. In this paper, we present a solution for the integration of declarative data validation rules with user

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... models in the domain of web applications, unifying syntax, mechanisms for error handling, and semantics of validation checks, and covering value well-formedness, data invariants, input assertions, and action assertions. We have implemented the approach in Web-DSL, a domain-specific language for the definition of web applications.