A central concern in the area of pervasive computing has been the integration 
of digital artifacts with the physical world and vice-versa. Recent 
developments in the field of embedded devices have led to smart things 
increasingly populating our daily life. We define smart things as digitally 
enhanced physical objects and devices that have communication capabilities. 
Application domains are for instance wireless sensor and actuator networks in 
cities making them more context-aware and thus smarter. New appliances such as 
smart TVs, alarm clocks, fridges or digital-picture frames make our 
living-rooms and houses more energy efficient and our lives easier. Industries 
benefit from increasingly more intelligent machines and robots. Usual objects 
tagged with radio-tags or barcodes become linked to virtual information 
sources and offer new business opportunities. As a consequence, Internet of 
Things research is exploring ways to connect smart things together and build 
upon these networks. To facilitate these connections, research and industry 
have come up over the last few years with a number of low-power network 
protocols. However, while getting increasingly more connected, embedded 
devices still form multiple, small, incompatible islands at the application 
layer: developing applications using them is a challenging task that requires 
expert knowledge of each platform. As a consequence, smart things remain hard 
to integrate into composite applications. To remedy this fact, several service 
platforms proposing an integration architecture appeared in recent years. 
While some of them are successfully implemented on some appliances and 
machines, they are, for the most part, not compatible with one another. 
Furthermore, their complexity and lack of well-known tools let them only reach 
a relatively small community of expert developers and hence their usage in 
applications has been rather limited. On the other hand, the Internet is a 
compelling example of a scalable global network of computers that interoperate 
across heterogeneous hardware and software platforms. On top of the Internet, 
the Web illustrates well how a set of relatively simple and open standards can 
be used to build very flexible systems while preserving efficiency and 
scalability. The cross-integration and developments of composite applications 
on the Web, alongside with its ubiquitous availability across a broad range of 
devices (e.g., desktops, laptops, mobile phones, set-top boxes, gaming 
devices, etc.), make the Web an outstanding candidate for a universal 
integration platform. Web sites do not offer only pages anymore, but 
Application Programming Interfaces that can be used by other Web resources to 
create new, ad-hoc and composite applications running in the computing cloud 
and being accessed by desktops or mobile computers. In this thesis we use the 
Web and its emerging technologies as the basis of a smart things application 
integration platform. In particular, we propose a Web of Things application 
architecture offering four layers that simplify the development of 
applications involving smart things. First, we address device accessibility 
and propose implementing, on smart things, the architectural principles that 
are at the heart of the Web such the Representational State Transfer (REST). 
We extend the REST architecture by proposing and implementing a number of 
improvements to fit the special requirements of the physical world such as the 
need for domain-specific proxies or real-time communication. In the second 
layer we study findability: In a Web populated by billions of smart things, 
how can we identify the devices we can interact with, the devices that provide 
the right service for our application? To address these issues we propose a 
lightweight metadata format that search engines can understand, together with 
a Web-oriented discovery and lookup infrastructure that leverages the 
particular context of smart things. While the Web of Things fosters a rather 
open network of physical objects, it is very unlikely that in the future 
access to smart things will be open to anyone. In the third layer we propose a 
sharing infrastructure that leverages social graphs encapsulated by social 
networks. We demonstrate how this helps sharing smart things in a 
straightforward, user-friendly and personal manner, building a Social Web of 
Things. Our primary goal in bringing smart things to the Web is to facilitate 
their integration into composite applications. Just as Web developers and 
tech-savvies create Web 2.0 mashups (i.e., lightweight, ad-hoc compositions of 
several services on the Web), they should be able to create applications 
involving smart things with similar ease. Thus, in the composition layer we 
introduce the physical mashups and propose a software platform, built as an 
extension of an open-source workflow engine, that offers basic constructs 
which can be used to build mashup editors for the Web of Things. Finally, to 
test our architecture and the proposed tools, we apply them to two types of 
smart things. First we look at wireless sensor networks, in particular at 
energy and environmental monitoring sensor nodes. We evaluate the benefits of 
applying the proposed architecture first empirically by means of several 
prototypes, then quantitatively by running performance evaluations and finally 
qualitatively with the help several developers who used our frameworks to 
develop mobile and Web-based applications. Then, to better understand and 
evaluate how the Web of Things architecture can facilitate the development of 
real-world aware business applications, we study automatic identification 
systems and propose a framework for bringing RFID data to the Web and global 
RFID information systems to the cloud. We evaluate the performance of this 
framework and illustrate its benefits with several prototypes. Put together, 
these contributions materialize into an ecosystem of building-blocks for the 
Web of Things: a world-wide and interoperable network of smart things on which 
applications can be easily built, one step closer to bridging the gap between 
the virtual and physical worlds.