The Internet of Things (IoT) paradigm envisions an interconnected world where things can communicate with each other, transmit state information and execute smart tasks. The number of devices connected in Internet has been growing exponentially in the past years and the Machine-to-Machine plays a major role in enabling IoT paradigm while it is expected that in the near future billion of devices will be connected. Till now many vertical solutions in the M2M domain exist. To bridge this gap , the European Telecommunications Standards Institute (ETSI) has defined SmartM2M a horizontal service layer that separates the communication part from the application domain and guaranteeing interoperability among different technologies. Each device independently from the technology should register and post data to the service layer, which makes them available to applications in a seamless way. However the integration with very constrained devices like a 6LoWPAN based network is not straight forward. In this paper at first it is analyzed the problem of the hierarchical Uniform Resource Identifier (URI) in the SmartM2M standard specifications. Then a new non hierarchical resource structure is presented which enables the use of very short overall URI for constrained devices.