In less than three decades, computers have evolved from bulky desktop units 
to tiny, embedded chips that can communicate wirelessly with each other. 
Battery-powered and stuffed with the latest sensing technologies, these 
networked embedded devices (NEDs) have been pervading our world and are 
increasingly implanted in our cars, buildings, and cities. From mobile phones, 
to surveillance systems, to contact-less payment systems - a legion of 
sentient machines continuously record our behavior. Analyzing the massive 
amounts of data collected by NEDs would be very valuable in many disciplines. 

Unfortunately, the usage of NEDs remains cumbersome because a multitude of 
hardware and software platforms have been developed - both in academia and 
industry - and the communication protocols supported by these platforms are 
often proprietary and incompatible with each other. Without a unified protocol 
to interconnect the various devices, building and maintaining large-scale 
applications that integrate NED data and services is an overly complicated 
process that requires extensive time, expert knowledge, and resources. A 
common infrastructure that can scale and evolve as new devices are added will 
be necessary to build a global network of NEDs installed and maintained by 
different actors. This in turn would lower the access barrier to develop 
distributed sensing applications (DSA) as devices could be shared and used 
easily. In this thesis, we address the integration problem in large-scale DSAs 
and explore how to simplify access to data and services of heterogeneous 
embedded devices. 

Nowadays, access to Internet has become cheap and ubiquitous and it is very 
likely that all sorts of electronic devices will increasingly possess Internet 
connectivity. Since the mobile Web is rapidly becoming a commodity, this 
thesis suggests that the existing Web infrastructure and its protocols should 
be leveraged to exchange data with NEDs. The tremendous success of the World 
Wide Web as a global platform for easily sharing information and connecting 
people to computing services attests that simple and loosely coupled 
approaches offer a high degree of scalability, robustness, and evolvability. 
This success is due to a large extent to an open and uniform interface which 
enabled non-experts to develop interactive hybrid applications rapidly. Unlike 
most protocols used in embedded computing, Web standards in the Internet are 
widely used and highly flexible, and in this thesis we suggest that this model 
would also be beneficial to future embedded computing applications. 

Our research bridges the fields of Web technologies and embedded sensing into 
a unified vision called the Web of Things - where the Web's well-known 
standards and tools are leveraged to seamlessly blend NEDs with the existing 
Web infrastructure. By drawing upon tools and techniques from both domains, we 
define the fundamental building blocks of the Web of Things as an extension of 
the current Web paradigms. After evaluating the limitations of current Web 
technologies with respect to the requirements of NED applications, we propose 
practical solutions to alleviate these difficulties to enable the development 
of efficient, event-driven, and scalable DSAs. Finally, we propose an 
end-to-end, fully Web-based framework that fosters fast prototyping of 
distributed sensing applications that run on top of heterogeneous NEDs. 

In contrast to existing research in sensor networks, the central question 
explored in this thesis is how much of the existing Web infrastructure can be 
reused to accommodate embedded devices. We further examine the common belief 
that Web standards are inappropriate for building efficient DSAs. Experimental 
results and prototypes are provided to support the hypothesis that using Web 
standards for NEDs is possible. Our results further show that the Web is not 
only a suitable, but actually a desirable medium to build distributed sensing 
applications that match the requirements for future large-scale sensing 
systems. 

We provide a comprehensive - conceptual and empirical - investigation of the 
usage of Web standards to exchange information with embedded devices, and the 
contributions of our work are multiple. First, our results are relevant to the 
sensor network and pervasive computing communities, as they support the 
hypothesis that the existing Web ecosystem is sufficient as is to build a new 
generation of scalable and flexible participatory applications on top of 
heterogeneous NEDs. Second, the Web community at large can build upon our set 
of guidelines to push the Web into the physical world by integrating devices 
in the Web fabric, thus making the idea of a Web API for the real world 
realistic. Third, we explore the practical usage of Web technologies in 
various contexts, from smart spaces to smart cities, and show that a fully 
Web-based infrastructure is an excellent basis to build an ecosystem of 
reconfigurable cyber-physical systems. Finally, we hope the work presented 
here will serve as inspiration for future Web developers and sensor network 
researchers. Bridging the gap between these two worlds will very likely shed 
light upon an unexplored design space to create more potent solutions for 
important societal problems, from energy-efficient buildings, to catastrophe 
detection and response systems, to more livable and enjoyable cities.