This paper describes how to use annotation to provide semantic information. The applications include the automatic construction of a GUI so that the user input is constrained to a correct range (guarding the input). Elementary GUI examples include elements for a variety of data types. Given sufficient effort, we envision the annotation technique as a replacement for XML and BeanInfo-based systems. We show that semantic annotation has several intrinsic benefits, geographically colocating constraints with their parameters eases maintenance, enables compile-time checking, and establishes consistent constraint declarations. Semantic annotation is shown to be GUI agnostic (devoid of Swing, SWT, AWT or HTML considerations). We also show how GUI annotation can be considered dangerous. The automatically constructed GUI’s are simple, and of no intellectual merit, other than their construction technique.