Originally code named \"Indigo\", WCF is one of four APIs introduced with the .NET Framework 3.0, in December 2006. WCF unifies several other communication APIs supported by the .NET Framework 2.0. Previously, separate APIs for SOAP-based communications for maximum interoperability (Web Services), binary-optimized communications between applications running on Windows machines (.NET Remoting), transactional communications (Distributed Transactions), and asynchronous communications (Message Queues) existed. WCF unified all these mechanisms into a single, common, general service-oriented programming model for communications. WCF can use SOAP messages between two processes, thereby making WCF-based applications interoperable with any other process that communicates via SOAP messages. When a WCF process communicates with a non–WCF process, XML-based encoding is used for the SOAP messages but when it communicates with another WCF process, the SOAP messages can be encoded in an optimized binary format. Both encodings conform to the fundamental information model of XML, the XML Information Set (XML Infoset). WCF uses a pluggable encoding system, allowing developers to write their own encoders.With the release of the .NET Framework 3.5 in November 2007, Microsoft released an encoder that added support for the JSON serialization format to WCF. This allows WCF service endpoints to service requests from AJAX-powered web pages.