Web Of Things

In this blog we are going to discuss

  • Web of Things and how it can be integrated with Physical things using known web technologies.
  • Implementing a World Wide Web of Things, which is a Web platform that enables tech-saavy users (i.e., proficient users of technology)
  • And visually create simple rules to compose Web sites and data sources.
  • We describe how these principles and tools can also be applied to empower the user to create physical Mashups on top of their things.

Creating networks of “smart things” found in the physical world (e.g.,with RFID, wireless sensor and actuator networks, embedded devices) on a largescale has become the goal of a variety of recent research activities. Rather than exposing real-world data and functionality through vertical system designs, we propose to make them an integral part of the Web. As a result, smart things become easier to build upon. In such an architecture, popular Web technologies (e.g., HTML, JavaScript, Ajax, PHP, Ruby) can be used to build applications involving smart things, and users can leverage well-known Web mechanisms (e.g., browsing, searching, bookmarking, caching, linking) to interact with and share these devices. In this blog, we describe the Web of Things (WoT) architecture and best practices based on the RESTful principles that have already contributed to the popular success, scalability, and evolvability of the Web. We discuss several prototypes using these principles, which connect environmental sensor nodes, energy monitoring systems, and RFID-tagged objects to the Web. We also show how Web-enabled smart things can be used in lightweight ad-hoc applications, called “physical Mashups”, and discuss some of the remaining challenges towards the global World Wide Web of Things.

From IOT to WOT

InternetOfThings_ETMAutomation

As more and more devices are getting connected to the Internet, the next logical step is to use the World Wide Web and its associated technologies as a platform for smart things (i.e., sensor and actuator networks, embedded devices, electronic appliances and digitally enhanced everyday objects). Several years ago, in the Cool Town project, Kindberg et al. (Kindberg et al. 2002) proposed to link physical objects with Web pages containing information and associated services. Using infrared interfaces or bar codes on objects, users could retrieve the URI of the associated page simply by interacting with the object. Another way to use the Web for real-world objects is to incorporate smart things into a standardised Web service architecture (using standards, such as SOAP, WSDL, UDDI) (Guinard et al.2010d). In practice, this would often be too heavy and complex for simple objects.

Instead of these heavyweight Web services (SOAP/WSDL, etc.), often referred to as WS-* technologies, recent “Web of Things” projects (Wilde 2007; Guinard et al. 2010c; Luckenbach et al. 2005; Stirbu 2008) have explored simple embedded Hypertext Transfer Protocol (HTTP) servers and Web 2.0 technology. In fact, recent embedded Web servers with advanced features (such as concurrent connections or server push for event notifications), can be implemented with only 8 KB of memory and no operating system support, thanks to efficient cross-layer TCP/HTTP optimisations, and can therefore run on tiny embedded systems, such as smart cards (Duquennoy et al. 2009). Since embedded Web servers in an Internet of Things generally have fewer resources than Web clients, such as browsers or mobile phones, Asynchronous JavaScript and XML (Ajax) has proven to be a good way of transferring some of the server workload to the client.

So far, projects and initiatives, subsumed here under the umbrella term “Internet of Things”, have focused mainly on establishing connectivity in a variety of challenging and constrained networking environments. A promising next step is to build scalable interaction models on top of this basic network connectivity and thus focus on the application layer. In the Web of Things concept, smart things and their services are fully integrated in the Web by reusing and adapting technologies and patterns commonly used for traditional Web content.

Resource-oriented Architecture and Best Practices

More precisely, tiny Web servers are embedded into smart things and the REST architectural style (Richardson and Ruby 2007; Fielding 2000) is applied to resources in the physical world (Guinard et al. 2010c; Luckenbach et al. 2005; Duquennoy et al. 2009; Hui and Culler 2008). The essence of REST is to focus on creating loosely coupled services on the Web, so that they can be easily reused. REST is the architectural style of the Web (implemented by URIs, HTTP, and standardised media types, such as HTML and Extensible Mark-up Language (XML) and uses URIs for identifying resources on the Web. It abstracts services in a uniform interface (HTTP’s methods) from their application-specific semantics and provides mechanisms for clients to select the best possible representations for interactions.

This makes it an ideal candidate to build a “universal” architecture and Application Programming Interface (API) for smart things. As we will explain in this blog, the services that smart things expose on the Web usually take the form of a structured XML document or a JavaScript Object Notation (JSON) object, which are directly machine-readable. These formats can be understood not only by machines, but are also reasonably accessible to people; provided meaningful markup elements and variable names are used and documentation is made available. They can also be supplemented with semantic information using microformats, so that smart things can not only communicate on the Web, but also provide a user-friendly representation of themselves.

SmartHome_ETMAutomation

This makes it possible to interact with them via Web browsers and thus explore the world of smart things with its many relationships (via links to other related things). Dynamically generated real-world data on smart objects can be displayed on such “representative” Web pages, and then processed with Web 2.0 tools. For example, things can be indexed like Web pages via their representations, users can “google” for them, and their URI can be emailed to friends or it can be bookmarked. The physical objects themselves can become active and publish blogs or inform each other using services, such as Twitter.64 The  general idea is that the Web is being used as a decentralised information system for easily exposing new services and applications, made possible, directly or indirectly, by smart things.

The Web-enablement of smart things delivers more flexibility and customisation possibilities for end-users. As an example, tech-savvy end-users, at ease with new technologies, can easily build small applications on top of their appliances. Following the trend of Web 2.0 participatory services, in particular Web Mashups (Zang et al. 2008), users can create applications mixing real-world devices, such as home appliances, with virtual services on the Web. This type of applications is often referred to as physical Mashup (Wilde 2007, Guinard et al. 2010c). As an example, a music system could be connected to Facebook or Twitter in order to post the songs one mostly listens to. On the Web, this type of small, ad-hoc application is usually created through a Mashup editor (e.g., Yahoo Pipes65 )

This content is extracted from book Architecting the Internet of Things by Dieter Uckelmann.

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