REST in Practice

Chapter 10. Semantics

WHEN BUILDING DISTRIBUTED APPLICATIONS ON THE WEB, you’ll see one thing is clear: document formats matter. The meaning, or semantics, behind the data and information in a document must be understood by both parties in an interaction in order to successfully achieve a business goal.

This chapter explores some of the possibilities raised by the advent of semantic technologies. It focuses on data, information, and the technologies that have emerged to help in integration scenarios. Semantics and Semantic Web are popular terms; here we show how they apply both to the example of Restbucks and more generally to building distributed systems on the Web. We’ll also briefly explore some popular technologies from the Semantic Web, including RDF and SPARQL.

Syntax Versus Semantics

Most distributed computing models enforce the structural or syntactic correctness of a system’s APIs and messages using interface or contract definition languages and message schemas. The semantics of these structural elements, however, is usually communicated through some other mechanism—typically a natural language specification. From a syntactic point of view, a <cost>2.0</cost> element is as good as an <a11119eb>2.0</a11119eb> element, just so long as both conform to the schema defined by the service provider. The difference is that the former is immediately meaningful to a human developer of an application, whereas the latter requires some interpretation—most likely involving reading ...