PRISMA is a resource-oriented publish/subscribe middleware for WSN, which the main goals are to provide: (i) programming abstraction through the use of REpresentational State Transfer (REST) interfaces, (ii) services, encompassing asynchronous communication, resource discovery and topology control, (iii) runtime support through the creation, configuration, and execution of new applications in WSN, and (iv) QoS mechanisms to meet applications constraints. This paper describes PRISMA architecture, its implementation in the Arduino platform, and a preliminary evaluation.