REST-based Web Services

Abstract

Web services are an important development in making data available to clients in a programmatic manner. Rather than displaying results for humans to view on the Web, we can make requests to a Web service in order to get the resulting data directly and then consume it in our applications immediately. An increasingly common architecture for Web services is termed REST and exploits the concept of URLs as resources. We can make general HTTP requests to retrieve, update, modify, and even create resources. The results (and sometimes the inputs) are often formatted as JSON or XML. In this chapter, we look at how we can access REST services from within R, mapping the documentation for the services into requests, converting the results, and developing R functions to provide higher-level interfaces that hide the details of the HTTP and conversion. REST is becoming the dominant mechanism used for Web services which are also becoming very common. REST is not just used for Web services, but is also increasingly used to communicate with regular applications such as NoSQLdatabases and text search engines and we explore these also in this chapter.