The matrix in Figure 20-2 ties together a number of the concepts we've been discussing.
Figure 20-2. A rendition can be generated from an abstraction
The top row contains two conceptual documents, as they might appear in your mind's eye. Actually, they are two states of the same document. The left column shows the document in its abstract state, while the right column shows it rendered.
The bottom row shows the computer representations of the abstraction and the rendition. The abstraction uses XML notation while the rendition uses HTML. The horizontal arrow indicates that the rendition was generated from the abstraction.
The diagram illustrates some important points:
Abstraction and rendition are two presentability states that a document can be in. Renditions are ready to be presented; abstractions aren't.
Renditions can be generated from abstractions automatically.
Markup languages can represent both abstractions and renditions; "structuring in XML" is no guarantee that you'll get an abstraction.
The computer representation of a document incorporates two ideas: presentability and notation. In other words, the representation of a document is either an abstraction or a rendition, and is either in an XML-based language or some other notation.
