An Introduction to eZ Publish Concepts
Tuesday 22 May 2007 1:00:00 am
eZ Publish adds yet another layer of abstraction to classic object orientation through the node concept. Abstraction here refers to how the system allows you to think of a news article without knowing how it is internally handled.
Content nodes
In eZ Publish, content objects are wrapped (or encapsulated) and structured using content nodes (or "nodes" for short). A node wraps a particular content object to provide a mechanism to access the data stored inside the object and display it on the website. Objects have no structural capabilities of their own. In other words, content objects cannot position themselves in relation to other objects. Wrapping a node around an object allows for this. In addition, nodes represent the published versions of content objects.
The following illustration shows a simplified example of a node and its encapsulated object as it would have been represented inside the system.
Content node tree
Nodes are organized in a node tree. The tree is divided into three major branches: the Content, Media and Users branches (and some other parts not frequently used by content editors). Most of the time, you will be working with the Content branch of the node tree. The node tree is also known as the content hierarchy, which is an important concept when creating new content.
The following illustrations show a simplified example of how objects are referenced by nodes to make up a content node tree, seen from the user perspective.
Content node tree
Content objects can be both individual objects and containers for content located beneath them in the content hierarchy. For example, one or more articles are generally stored beneath a folder. When the folder is displayed, it automatically displays a summary list of the articles stored beneath it. Each content class has a different template for displaying objects of that class. Therefore, while a folder displays some attributes of the objects located beneath it in the hierarchy, an article will not necessarily do the same.