This paper proposes a declarative description of user interfaces that abstracts from low-level implementation details. In particular, the user interfaces specified in our framework are executable as graphical user interfaces for desktop applications as well as web user interfaces via standard web browsers. Thus, our approach combines the advantages of existing user interface technologies in a flexible way without demands on the programmer’s side. We sketch an implementation of this concept in the declarative multi-paradigm programming language Curry and show how the integrated functional and logic features of Curry are exploited to enable a high-level implementation of this concept.