Coordination via tuple spaces is a well known and accepted technique for designing distributed systems; originally introduced in Linda, it has been very recently adopted within the Java environment as underlying mechanism of the JavaSpaces TM technology. Here we explore the possibility of using such technique in the development of systems adopting the UML notation. While tuple spaces are modelled quite naturally in UML as particular classes, state machines do not seem adequate for modelling active objects interacting via tuple spaces. Thus, we propose to extend state machines by adding transition triggers corresponding to successful and failed execution of lookup operations on a tuple space. The result is a UML profile, and thus a visual notation, for modelling distributed systems based on tuple spaces.