In this paper we analyze the problem of “situating explanations” in user assistance systems. We introduce semantic transparency as a user interface property that enables giving appropriate help. We explicate this notion in document player applications found in office suites, for example. Moreover, we show how semantic transparency can be strengthened when the underlying software is complemented by a semantic ally system. The approach consists in illustrating existing software semantically. We present some semantic extensions of office applications as examples. We also describe how the semantic transparency approach allows the exploitation of new interactions for user assistance systems. Categories and Subject Descriptors H.5.2 [Information Systems]: Information Interfaces and Presentation—Interaction styles; H.5.2 [Information Systems]: Information Interfaces and Presentation—User-centered design; D.2.2 [Software]: Design Tools and Techniques—User interfaces General Terms Do...