## 7 Using IETF Standards to Realize the Internet of Things
### Realizing the Web of Things  
To allow the integration of an increasingly large number of IoT devices, self-configuration protocols will be required. Solutions for self-configuration such as [97] allow newly deployed constrained devices to be automatically discovered, automatically assign DNS hostnames and transparently make the IoT resources directly accessible and browsable over IPv6 via HTTP or CoAP.  
Figure 16: IETF LLN protocol stack.  
Alternatively, devices can add their resources to a publicly accessible directory service. This sort of solution forms an important building block that facilitates the actual usage of embedded web services (without human intervention) as is required for realizing the Web of Things (WoT). For instance, a client can automatically be notified about new resources and continuously observe the state of a resource using the CoAP observe extension [89], leading to a consistent representation of all resources of interest. Using conditional observations [117], interested parties can be notified about resource states that satisfy specific conditions, thereby acting as an enabler to build applications such as sensor--actuator interactions. These extensions enrich the capabilities of the basic CoAP protocol and contribute to the realization of the WoT.  
Another important research domain focuses on web service composition whereby different IoT services are combined to realize complex goals. For instance, embedded web services can automatically be combined to create complex interaction scenarios where knowledge about the real world is used, linked with other services and processed to act again upon the physical world. Existing composition and orchestration frameworks such as described in [141], need to be extended in order to realize the WoT. The main challenge is the adaptation of existing web service composition models to take into account the limitations of constrained devices. Also, when time varying data from constrained objects is incorporated or web services act upon the real world, issues such as consistency, failures, correct execution of all transactions as described in [142] need to be explored in view of a constrained environment.  
The link between the IoT and state-of-the-art cloud technology solutions is made clear in [143]. Cloud technology can be used for collecting, storing and processing the enormous amount of sensor data. Tiny objects can also be introduced as part of grid computing e.g., for the collection and processing of environmental information. In [144] an extensive overview of the introduction of mobile devices into Grid systems is given and an extension to the constrained world seems feasible with the advent of embedded web service technology.  
It is clear that the step from Internet of Things towards a Web of Things will be taken sooner rather than later. The IoT can facilitate the realization of the WoT, opening up access to sensor data and stimulating their widespread usage, while at the same time avoiding vertically integrated and closed systems. As such, it presents great opportunities to researchers active as well in the field of web service technology as in the field of embedded distributed systems.