1. A computer-implemented method for providing a visual editor allowing graphical editing of expressions in an expression language, comprising: displaying a graphical user interface; receiving a first user input of an expression, the expression being defined in a logical or textual form, wherein each component of the expression is represented by a graphical element on the graphical user interface; verifying a syntax of the first user input; and providing an alert to the user in response to detecting a syntax error or an inconsistency of the first user input when verifying the syntax.