What is Schema?
According to Murray in her text, Inventing the Medium, a schema is an abstract, organized representation of knowledge. Schema can apply to many different forms, such as the structure of a language, or to computational objects like XML schemas. A well-known example of classification schema is the Dewey Decimal system, which is a library classification system. Basically, using schema is just an effective way to define the structure and the content of your documents, and is used mostly for organizational purposes.