Most sites you visit have a web service running in the background
These services allow you to integrate data between sites through API’s such as you see on Flickr and Amazon
A web application combines data from more than one source into a single integrated tool; an example is the use of cartographic data from Google Maps to add location information to real-estate data, thereby creating a new and distinct web service that was not originally provided by either source
The Resource Description Framework (RDF) is a family of World Wide Web Consortium (W3C) specifications, originally designed as a metadata data model is now accepted as a general method of modeling information through a variety of syntax formats.
The RDF data model is based upon the idea of making statements about resource Web resources in the form of subject-predicate-object expressions, called ''triples'' in RDF terminology