ترکیب فن آوری های خدمات ناهمگن برای ساخت و ساز اینترنت از میان افزارها

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.

For the last decade, technological progress has led to miniaturization of computer resources. Processors, memory and data storage are now embedded on small devices spread in the environment. As these devices are more and more equipped with communication capabilities, they tend to be integrated to larger systems. Some objects with communication and sensing capabilities can produce measurements and provide information systems with data on the physical world. Radio-frequency identification (RFID) technology allows ordinary objects equipped with radio-frequency tags to be uniquely and remotely identified. RFID tags are able to store identifiers and small quantities of data associated to a given object (e.g., the credit balance of a skipass, a URL in an NFC smart poster). The MIT Auto-ID Center, one of the major actors in RFID systems standardization, coined the term “Internet of Things” [2] for referring to a network where objects would be individually and instantly identified with RFID tags to form an Internet of Things. However, the standards produced by the MIT Auto-ID center, and EPCglobal (non-profit consortium that controls such standards) were strongly coupled with RFID as the means of product identification. They target mainly supply chains and goods traceability, allowing easily querying to find information about a specific product. However, RFID tags themselves are not able to provide the aforementioned sensing capabilities. Different wireless and mobile technologies play an important role for bringing an enhanced vision of the Internet of Things (IoT) a step further: in a wider sense, the idea of an IoT evolved as to refer to a ubiquitous object society where different objects are connected, combining RFID, sensor networks and ubiquitous technologies to achieve this concept [30]. RFID laid the initial bricks for such IoT, by allowing to uniquely identify and to store information about individual objects. However, the IoT is not only limited to RFID but could have similar functionality by using different types of object identification [31] such as standards like linear barcode and datamatrix. Not only objects that participate in a supply chain should be traceable in the IoT. As many others, we believe that ordinary objects either through their own means (e.g., smartphones) or by other means of connectivity should also take part in this Internet of Things. As a consequence of this evolution, software engineering should propose innovative infrastructures fulfilling the requirements related to the nature of the Internet of Things, which are among others: heterogeneity (e.g., different objects, sensors, protocols and applications), dynamicity (e.g., arrival and departure of objects and sensors) and evolution (e.g., support for new protocols, sensors). At the same time, service-oriented computing (SOC) [22] has also become a major research topic drawing the attention of academics and industrials. A service-oriented architecture (SOA) brings loose coupling and flexibility to applications, and allows the seamless integration of heterogeneous platforms and applications. Dynamic platforms such as the OSGi service platform, which also applies service-oriented principles, provide the ability of dynamic evolution of code (i.e., component updates at application runtime). For these reasons, SOC seemed as a good way to tackle the above issues. Hence the purpose of this paper, which is the experimentation of leveraging a middleware for the Internet of Things by using service-oriented computing (SOC) for building it. The role of the middleware is to track not only RFID-tagged objects but also other objects that can provide relevant information. The data mediation to be performed should handle the data produced by such objects forwarding them to information systems using existing standards. The proposed middleware, simply called RFID suite, was designed on a multi-layer architecture with SOC being present at each tier, and as a way for integrating them. The novelties and contributions that can be identified in our approach are: the service-oriented and multi-layer architecture in an RFID context; the dynamicity and flexibility of the SOC approach in the data collection layer; the protocol flexibility introduced in the intermediate layer; and the web service-oriented object naming service. This work has been conducted at the University of Grenoble, France, and it has been open sourced in the OW2 AspireRFID1 project, part of the ASPIRE FP7 project.2 The remainder of this paper is structure as follows: the next section provides some background for understanding this article and explains the motivations behind the creation of a service-oriented middleware for the Internet of Things. Section 3 details the architecture of the RFID suite, and how SOC is used to implement the different middleware layers. Afterwards, Section 4 presents several validation scenarios where our middleware was used, and Section 5 discusses the effectiveness of the approach relying on SOC as well as the lessons learned concerning the encountered limitations of our approach. Section 6 overviews other approaches that are related to the RFID suite, and finally, Section 7 draws the conclusions and final considerations.

Internet of Things is a term initially related with RFID tagged objects. This concept has evolved in a wider sense, referring now to a ubiquitous object society combining RFID, sensor networks and pervasive computing technologies. The usage of serviceoriented computing is suitable for such a highly dynamic scenario where a strong decoupling between components, as well as between applications, is imperative for allowing evolutive systems and architectures. This report aimed at evaluating the benefits of service-oriented computing principles for conceiving and realizing a middleware designed to enable an Internet of Things, leveraging the dynamicity and flexibility of such middleware. Besides the RFID identifiers typically supported, our middleware also supports ordinary objects uniquely identified to be tracked. The usage of SOC brought positive results turning out to be a suitable solution to tackle issues raised by pervasive computing and the Internet of Things. Our RFID middleware achieved a significant level of flexibility in different levels of the architecture. At the edge level for the seamless integration of sensors and readers. Adding or removing readers at runtime in a running edge already provides a good level of flexibility. The service-oriented readers provide higher flexibility since they can adapt non-RFID objects and data from external application, when using the RESTful reader, as well as plug and play readers, when using the UPnP approach. The middleware architecture itself allows layers to communicate using service-oriented technologies, introducing a high level of decoupling between the different system layers and allowing to easily replace entities reified as services (e.g., readers, sensors, servers) with minimal system disruption. The data mediation chain between information systems and pervasive systems is easily and dynamically adaptable, allowing protocol changes on the fly and reconfiguring the message routing. The utilization of web services for integrating servers also brought significant results, enabling a stronger decoupling between the different applications that compose the architecture, and allowing reuse of EPCIS information by third-party applications. However some improvements could be made by adapting an ESB in the middleware mediation layer in contexts, where complex event processing or service orchestration would be more appropriate than our custom mediation approach. However on the bright side we support several transport protocols and do not rely only on HTTP/SOAP, which is the typical (as well as limiting) choice in service-oriented architectures. The middleware presented in this paper has been validated and used in various scenarios. It allowed us to verify its extensibility, flexibility, and the quick learning curve considering its usage in practical classes. The integration and support of devices which are available on the public market, and the facilitated integration of new devices has shown that this RFID suite is particularly well-suited for rapid application prototyping. Especially when there is a need to design sensor-based and RFID-based applications that need both a well-grounded lower layer to manage devices and a management infrastructure to collect and use the data, with the possibility to remotely administrate each component of the middleware, and to visualize data through higher level administration consoles (e.g., web console) that could be easily replaced. The RFID suite has been contributed in the OW2 AspireRFID middleware open-source project, which is part of the ASPIRE European project. AspireRFID had its architecture partly influenced by the principles used in the RFID suite here described. Ongoing and future work includes migrating into AspireRFID the positive architectural points highlighted by this experiment, including the entire sensor infrastructure, from the edge layer to extended ALE EC specs and reports, and the GUI for tracking and monitoring objects and measurements.