Provisioning of applications and value-added services for mobile (remote) monitoring and access to measurements data is supported by advanced communication models such as Internet of Things (IoT). IoT provides ubiquitous connectivity anytime and with anything. IoT applications are able to communicate with the environment, to receive information about its status, to exchange and use the information. Identification of generic functions for monitoring management, data acquisition, and access to information provides capabilities to define abstraction of transport technology and control protocols. This chapter presents an approach to design Web Services Application Programming Interfaces (API) for mobile monitoring and database access. Aspects of the Web Services implementation are discussed. A traffic model of Web Services application server is described formally. The Web Services application server handles traffic of different priorities generated by third party applications and by processes at the database server's side. The traffic model takes into account the distributed structure of the Web Services application server and applies mechanisms for adaptive admission control and load balancing to prevent overload. The utilization of Web Services application server is evaluated through simulation.
TopIntroduction
The advance of Internet from a network of interconnected computers and mobile terminals, to a network of interconnected objects (things) enables provisioning of applications and value added services for mobile monitoring. Within the paradigm of Internet of things (IoT), the objects have their own IP addresses and identifiers, may be embedded in complex systems and use sensors (ITU, 2005; INFSO, 2008). These “smart” objects are able to recognize each other, communicate with the environment, receive information about its status, exchange and use the information. The communication between objects may be limited to particular areas (Intranet of things) or may be publicly accessible (Galluccio, 2011; Li, 2012; Wang, 2013). The ubiquitous connectivity of objects requires integration between heterogeneous sensors as sources of information. Usually in IoT applications, sensors provide information from physically distributed dynamic processes and their interoperability appears to be a real challenge.
Extending IoT with the Web Services technology is a way to achieve interoperable communications between objects (Castellani, 2011). Web Services feature automated service discovery and composition as well as the ability to deal with heterogeneous sources of information. Embedding Web Services into IoT objects eases the integration of distributed dynamic processes. Embedded Web Services may be regarded as physical information servers in constrained nodes. They follow the REpresentational State Transfer (REST) style of software architecture for distributed systems. The usage of efficient payload encoding and Web linking format for constrained Web servers improves the performance of embedded Web Services (Shelby, 2012).
A lot of academic research has been conducted in the field of mobile monitoring services. However, most of the research studies different ways to collect and evaluate data, and different privacy issues that are related to data collecting but the distribution of data to third parties has had less attention. Fox, Kamburugamuve and Hartman (2012) suggest architecture of IoT system, where Web Services Application Programming Interfaces (APIs) are defined between sensors and a central controlling unit, and between the central controlling unit and applications. Works related to embedded Web services for IoT applications consider different application domains (Elgazzr, 2012; Agarwal, 2010, Ryu, 2012). Design of Web Services for IoT applications requires identification of generic functions for monitoring management, data acquisition and data transfer, and access to information. The synthesis of generic functionality allows definition of abstraction that is independent of transport technology and control protocols.