FADO 2.0 is a high language, developed in the context of the 4th level trigger of the DELPHI data acquisition project at CERN, that provides a simple and consice way to define physics criteria for event tagging. Its syntax is based on mathematical logic and set theory, as it was found the most appropriate framework to describe the properties of single HEP events. The language is one of the components of the FADO tagging system. The system also implements implicity a mechanism to selectively reconstruct the event data that are needed to fulfil the physics criteria, following the speed requirements of the online data-acquisition system. A complete programming environment is now under development, which will include a syntax directed editor, and incremental compiler, a debugger and a configurer. This last tool can be used to transport the system into the context of other HEP applications, namely offline event selection and filtering.