Items by Wilde, Erik

This introduction presents the schedule, the tutorial presenters, and some background for the tutorial. Specifically, we briefly mention all the *OA terms that have been invented in recent years, such as SOA (Services), ROA (Resources), WOA (Web), SynOA (Syndication), and EOA (Event), and briefly set them into context. Our main goal is to explain our notion of SOA for the purpose of this tutorial, and what we perceive as the core tasks when moving from SOA to REST.

REST's level of abstraction and its simplicity as a small set of constraints can make it hard to get a grasp on how it can be applied for real-worl projects. This presentations introduces real-world REST by looking at how REST ce be used by reusing existing RESTful designs in terms of representations and interaction protocols; Atom and the Atom Publishing Protocol (AtomPub) are used as examples for existing RESTful designs. In addition, we take a brief look at how to go beyond using these canned REST approaches, and how existing programming framework provide support for designing and implementing RESTful services.

Representational State Transfer (REST) is defined as an architectural style, which means that it is not a concrete systems architecture, but instead a set of constraints that are applied when designing a systems architecture. We briefly discuss these constraints, but then focus on explaining how the Web is one such systems architecture that implements REST. In particular, the mechanisms of the Uniform Resource Identifiers (URIs), the Hypertext Transfer Protocol (HTTP), media types, and markup languages such as the Hypertext Markup Language (HTML) and the Extensible Markup Language (XML). We also introduce Atom and the Atom Publishing Protocol (AtomPub) as two established ways on how RESTful services are already provided and used on today's Web.

Loose coupling is often quoted as a desirable property of systems architectures. One of the main goals of building systems using Web technologies is to achieve loose coupling. However, given the lack of a widely accepted definition of this term, it becomes hard to use coupling as a criterion to evaluate alternative Web technology choices, as all options may exhibit, and claim to provide, some kind of “loose” coupling effects. This paper presents a systematic study of the degree of coupling found in service-oriented systems based on a multi-faceted approach. Thanks to the metric introduced in this paper, coupling is no longer a one-dimensional concept with loose coupling found somewhere in between tight coupling and no coupling. The paper shows how the metric can be applied to real-world examples in order to support and improve the design process of service-oriented systems.