Thus far, we have discussed the use of the IP architecture as the means by which smart objects are connected. We have discussed how the IP architecture is built, how IP works with message routing, and how IPv6 fits the requirements for smart objects exceptionally well. But we have not yet discussed how these technologies are used to create smart object systems, and how smart objects can be integrated into existing IT systems. In this chapter, we take a look at web services - a technology by which smart objects can be efficiently integrated into existing IT and enterprise business systems.
Web services are a framework for building distributed applications. They have typically been used to build applications that either interact using a web browser, or are somehow related to the World Wide Web. But the technology that makes up web services is not tied to the World Wide Web or the particular technology that typically is associated with it, such as web browsers.
Web services are typically explained using examples from popular services that are used on the Web, such as flight travel booking systems, online book stores, or web searches. Even though those applications may sound removed from smart object systems, their inherent application properties are surprisingly similar to those in smart object systems. Web-style applications and smart object applications share many of the basic communication properties: they are composed of separate systems that exchange data.
Given the prevalence of the Web and its associated technologies, web services have seen a tremendous adoption in the general purpose IT world in the past couple of years. All major programming languages provide libraries tailored to build web-service-oriented applications. Hence, a large body of existing IT systems is built using web services. There are numerous online courses and other training material available to learn how to build web service applications.
Web services have traditionally been seen as a technology suitable for big servers, big datasets, and big systems. This technology has been used to couple database systems with each other in a framework that permits an expression of high-level concepts and dependencies, and yet is succinct enough to be standardized across a wide range of applications.
By using web service technology for smart object applications, existing web-service-oriented systems, programming libraries, and knowledge can be directly applied to the emerging field of smart object applications. This provides several benefits.
For businesses, smart object applications can be directly integrated with existing business systems and use the same interfaces and systems existing business systems use. This makes it possible to integrate smart object applications into enterprise resource planning systems without any intermediaries, thus reducing the complexity of the system as a whole. For industries, smart object applications can be built using off-the-shelf technology without any customized interfaces or translators. Systems can be built without requiring smart object specialists in every step of the project.
In this chapter, we discuss the use of web service technology for smart objects. Because of the expressiveness of the underlying principles, web services are highly suitable for smart objects. Despite the dominating belief that web services are a heavyweight concept, we demonstrate that they are indeed lightweight enough to be used for the resource-challenged environment in which smart objects exist. We do not discuss the details of web services in this chapter, however, as the concepts and the surrounding technology and its software are extensive and diverse. We keep the discussion at a relatively high level, and refer to more specialized publications for further details.
We examine the technology and principles behind web services, how they map onto smart object concepts, and how they can be efficiently implemented for smart objects. To ground the discussion, a concrete example of an existing web service for smart objects is provided: the Pachube service is a data-hosting service for smart-object-style applications where data are inserted and accessed using web service technology.
The performance of web services for smart objects has been questioned, because web services were initially used for large server systems. At the end of this chapter, we critically examine this by discussing the performance of published web service implementations for smart object systems. We find that the performance of web services for smart objects is indeed reasonable.