# Performance and Challenges of Service-Oriented Architecture for Wireless Sensor Networks
## 7 Service-Oriented Architectures Approaches for WSNs
### Other Approaches
A multi-SOA approach is designed to increase the efficiency and QoS of the system [36]. The WSN-SOA, a multi-level based on the existing SOA on the higher tiers with a protocol stack is presented in [36]. The SOA has the capability to handle the nodes with low capacity without generating an overhead of XML-based technology. WSN-SOA allows the SOA-based communication of low capacity sensors in the networks as MICAz motes. The multi-level via auto-configuration can enable all sensors to turn into reusable resources and allow the distributed collaboration between them. The \"software stacks\" help link between low capacity and full capacity nodes [36]. The extension of WSN-SOA stacks is introduced in [36]. It supports dynamic deployment of Service-Oriented cooperative tasks in the networks efficiently. The WSN-SOA is implemented on open source operating system TinyOS 2.1 (TinyOS Alliance) and develops WSN-SOA for Crossbow MICAz (Crossbow Technology, Inc., Milpitas, CA, USA) [37]. Similarly, the x-SOA approach [85] is related to previous approaches. There is X-SOA framework for sensor web service discovery mechanism, which is based on the Natural Language Query Processing (NLQP) by using semantic grammar [85]. The framework acts as the intermediate layer, called RPQ (Request Parser & Query generator), which supports interoperability between the service requester and the service registry [85]. A novel algorithm called Sensor Web Registry Services Discovery (SWRSD) is used in all steps of the processes of sensor service discovery [85]. The different layers can interact with each other by Unified Modeling Language (UML) sequence diagrams. The limitation of this architecture considers only the QoS function but does not deal with QoS non-functional. The non-functional is known to provide efficiency to the sensor web registry. In [86], the authors used the same mechanism and added QoS non-functional to the sensor web registry. Multi-layers of SOA framework are proposed for Sensor Web Service Discovery (SWSD) mechanisms that are based on the Natural Language Query Processing (NLQP) [86]. The architecture reduces the burden of novice requesters. The overhead decreases by converting user requests in XML or SOAP to other formats. The architecture has fewer capabilities for dealing with other QoS or for supporting different types of sensor web services. The limitation of this approach is that it tests only five sensor nodes and should be evaluated with additional sensors to obtain more QoS parameters. The power consumption, data aggregation, and delay should be considered with this approach. The studies [87; 88] proposed a generic framework approach based on web service which can be built as a standardized interface between external networks, applications, and WSNs. The implementation is based on Direct Service-Oriented Diffusion (DSOD) and the Service-Oriented Routing Protocol for WSN [87; 88]. The SOA is implemented on the sensors. The security services are addressed in this architecture and provide Authentication, Authorization, and Accounting (AAA) mechanisms. The drawback of this approach is that accuracy is not considered. The name-centric service architecture framework based on the data/Content-Centric Network (CCN) for cyber physical system (CPS) can address the limitation provided by using transparent methods for accessing the services in the CPS. It implements a lightweight approach for WSNs which is called Content-Centric Networking Protocol for WSN (CCN-WSN) and can easily implement a gateway between CCN-WSNs and CCNx to build the SOA [89]. This approach still has limitations due to the named services requiredwhen coordinating naming in CPSs. This drawback should be addressed by using standard naming system for the CPSs. The NanoSD is a service discovery protocol which designed for mobile, dynamic, and heterogeneous of WSNs [90]. The implementation of NanoSD provides a lightweight service discovery protocol for WSNs [90].