What is Architectural Style

Current integration solutions are still based on technologies developed for the original Web problem, which is browsing remote hypermedia documents with text as the main media type. Text-based data descriptions such as XML and JSON and stateless and connectionless protocols such as HTTP are still the norm to achieve distributed integration. However, the Web today is much more dynamic, in that resources are no longer passive hypermedia documents but are active and implement services. SOA and REST are the most used architectural styles to implement distributed integration, and each exhibits advantages and disadvantages. This chapter illustrates that they are dual architectural styles—one oriented towards behavior and the other towards state—and contends that it is possible to combine them to maximize the advantages and to minimize the disadvantages. A new architectural style, designated Structural Services, is proposed and described. Unlike REST, resources are able to offer a variable set of operations, and unlike SOA, services are allowed to have structure. To minimize resource coupling, this style uses structural interoperability based on the concepts of structural compliance and conformance, instead of schema sharing (as in SOA) or standardized and previously agreed upon media types (as in REST). To delineate how this style can be implemented, a new distributed programming language is presented.