Items by Pautasso, Cesare

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.

In this part we summarize the WS-* vs. REST debate by giving a quantitative technical comparison based on architectural principles and decisions. We show that the two approaches differ in the number of architectural decisions that must be made and in the number of available alternatives. This discrepancy between freedom-from-choice and freedom-of-choice explains the complexity difference perceived. However, we also show that there are significant differences in the consequences of certain decisions in terms of resulting development and maintenance costs. The comparison helps technical decision makers to assess the two technologies more objectively and select the one that best fits their needs: REST is well suited for basic, ad hoc integration scenarios, WS-* is more flexible and addresses advanced quality of service requirements commonly occurring in enterprise computing.

REST is simple to define, but understanding how to apply it to design RESTful services is more difficult. The goal of this part of the tutorial is to present the main design elements of a RESTful architecture and introduce a design methodology for RESTful services. A selection of useful patterns and anti-patterns will be discussed with some examples that will be further developed in the practical part.

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.