"Rich Enterprise Applications (REA) creates a new class of enterprise Web 2.0 applications. REA solutions leverage the usability and increased functionality of RIA applications and extends their reach beyond the browser and into the organization’s Service Orientated Architecture(SOA) assets.
REAs leverage an organization’s investment in SOA with enterprise Web 2.0 technologies that enable new business and application models such as Software as a Service (SaaS), enterprise mashups, next-generation portals, and browser-based deployment of enterprise applications – all with robust scalability, security, and desktop-like interactivity on the client side utilizing AJAX."
It continues and notes that just because an enterprise has AJAX and SOA, doesn't neccessarilly mean they have an REA. For the enterprise, there are three additional components RIA does not require but REA does.1. User-driven Integration
2. Service Governance - "I think this is the real differenciater between RIA and REA."
3. Enterprise Grade Communication Channel