monitoring (earthquakes, floods, radiation areas, fire, rainfall) [ 6 ], smart cities, smart
buildings, smart homes, health-care, to name a few.
Some middleware platforms already exist, addressing one of the main challenges
to enable realization of IoT: interoperability across heterogeneous resources to relieve
the application developer from the burden of integrating them. However, according
to [ 5 ], the existing proposals do not cover the full set of functionalities to meet the
requirements of an IoTmiddleware. In addition, most of them are under development
and did not reach the stage of maturity to be adopted in a large scale.
This topic described a middleware-layer infrastructure, SmartSensor, that focuses
on the integration of Wireless Sensor Networks (WSN) in the Web, providing WSN
as a service, acessible as any other Web resource and enabling the discovery and
composition of services to formWeb mashup applications. In fact, this infrastructure
targets a significant barrier to the widespread use of WSNs, that is the complexity of
applications development that need to deal with low-level concerns of WSN. One of
the fundamental characteristic of SmartSensor is to be based on the REST (Represen-
tational State Transfer) principles [ 2 ] and to useWeb standards and protocols, such as
URIs (Uniform Resource Identifier) and HTTP (Hypertext Transfer Protocol). This
is especially useful for the integration of WSN to the Web, since the heterogeneous
nature of their devices. In SmartSensor, WSNs are connected to the Web through
a gateway node and their data are exposed as RESTful Web resources. Therefore,
the interactions occurs in a RESTFull style by using the set of simple, well-defined
HTTP main operations (GET, POST, PUT and DELETE i.e. the verbs of REST).
Currently, SmartSensor supports three different platforms that are proper to a WSN
scenario typically endowed with several tiny and low-power networked devices in
interaction.: Arduino, 1 Sun SPOT, 2 and motes from the MICA family (produced by
MEMSIC, former Crossbow), 3 based on the TinyOS operating system, 4
designed to sensors.
The infrastructure provided by SmartSensor to seamless integrate the resources
relies on three main building blocks:
1. The Sensor Integration Module (SIM) integrates the distinct WSN devices and
provides a RESTfull interface to access them as Web resources. It enables data
collection and delivery and supports publish and discovery of WSN services.
SIM components are deployed both in sensor nodes and in gateways nodes.
2. The Programming and Execution Module (PEM) enables the composition of
value-added services from multiple Web sources, mixing public available ser-
vices and those provided by SmartSensor that are registered in SIMs. PEMoffers
aDSL (Domain Specific Language) based on the EnterpiseMashupMarkup Lan-
guage (EMML) [ 1 ] and an interpreter for such DSL. It provides mechanisms to
create, interpret, and execute Web mashups specified via EMML scripts.