Connecting our physical world to the Internet is the ambitious
vision of the Internet of Things. Embedding sensors and actuators
into arbitrary "things" and connecting them to the Internet enables
the location-independent monitoring, controlling, and programming of
the physical world on an unprecedented scale, often in real time.
Beyond connectivity, the ability of devices to interoperate with
other devices and services will be an important requirement in a
future Internet of Things - the sheer number and heterogeneity of
Internet-connected things renders manual integration infeasible.

Based on the existing architecture of the World Wide Web, the
so-called Web of Things addresses the challenge of interoperability
for Internet-connected things. By leveraging existing Web standards
and infrastructure, one can benefit from the many aspects that have
already been covered in the Web architecture as well as from the
plethora of existing Web services and Web-enabled applications.
Exposing physical entities, in particular their sensors and
actuators, on the Web in order to provide an interface for retrieving
and changing the state of such entities and their environment is a
well-known concept. With the increasing amount of Internet-connected
devices and the advent of novel standards and services, this concept
has recently gained momentum but has also shown the limitations of
existing approaches.

This thesis addresses this development by providing the following
contributions to a future Web of Things:

- The development and evaluation of a prototypical real-time search
engine for the physical world that is based on the Web
architecture. In contrast to traditional Web search engines, a
search engine for the physical world has to support searching for
structured and rapidly changing, distributed state in real time. The
proposed solution is based on an open architecture and requires
neither a global view of the world.s state nor a limitation of the
search space while still providing accurate results in real time.

- A prototypical framework for the Web of Things that simplifies the
connection of sensors and actuators to the Web as well as their
composition to novel services. It provides key primitives identified
during the development of several experimental applications. The
proposed solution does not advocate a central hub but strives to
enhance today.s inherently decentralized Web architecture.

- A concept of connecting everyday objects directly to the Web that
leverages the ubiquity of Wi-Fi access points and the
interoperability of the HTTP protocol, utilizing programmable
low-power Wi-Fi modules. Using a loosely coupled approach, the
seamless association of sensors, actuators, and everyday objects
with each other and with the Web is enabled. Experimental results
show that low-power Wi-Fi modules can achieve long battery lifetime
despite using the resource-intensive protocols and data formats of
the Web for communication.

In summary, this thesis demonstrates that leveraging the Web.s
architecture in order to address interoperability in a future
Internet of Things is a promising concept by covering several
aspects of this development.