Abstract. In this paper we present an approach for oblivious composition of Web user interfaces, particularly for volatile functionality. Our approach, which is inspired on well-known techniques for advanced separation of concerns such as aspect-oriented software design, allows to clearly separate the design of the core’s interface from the one corresponding to more volatile services, i.e. those that are offered for short periods of time. Both interfaces are oblivious from each other and can be seamlessly composed using a transformation language. We show that in this way we simplify the application’s evolution by preventing intrusive edition of the interface code. Using some illustrative examples we focus both on design and implementation issues, presenting an extension of the OOHDM design model which support modular design of volatile functionality