Radio-frequency identification (RFID) is a technology that allows ordinary objects to be uniquely identified by "smart tags" which are also capable of storing small quantities of data. The term Internet of Things was originated from a vision strongly coupled with supply-chain concerns and RFID tagged objects. However the idea of such Internet of Things has evolved in a wider sense, referring now to a ubiquitous object society combining RFID, sensor networks and pervasive computing technologies. This scenario involves different requirements such as heterogeneity and dynamicity of objects, sensors, applications and protocols as well as the need for allowing the dynamic evolution of such applications. These issues seemed to be easily addressed if the principles of service-oriented computing (SOC), like loose coupling and heterogeneity, are used for constructing such architectures and applications. In this paper we underline what benefits SOC can offer to constructing a middleware for the Internet of Things. These concepts have been applied in a service-oriented middleware that tries to leverage the existing Internet of Things architectural concepts by using SOC principles in order to bring more flexibility and dynamicity. We describe the approaches used in that middleware and the lessons learned from that experience. This middleware was initially tested on an application for tracking and monitoring supply-chain objects, and later extended to target wider application domains that are also described in this paper. The project described here has become part of the OW2 AspireRFID open-source project. (C) 2011 Elsevier B.V. All rights reserved.
