Cross Publishing Content in eZ Publish
Thursday 09 August 2007 3:00:00 am
Content objects, nodes and the content hierarchy
Cross publishing is based on the mapping between content objects and nodes within the content hierarchy (also called the node tree). Recall from the first article in this series that content objects are wrapped inside (or encapsulated) and structured using content nodes (or just "nodes" for short). The following illustration shows a simplified example of a node and its encapsulated object as it is represented inside the system.
Object - node relation
Nodes are organized in a node tree, storing all published content in a hierarchy. A node provides a location for a content object within the tree structure, and refers to exactly one content object. However, an object can be referenced by several nodes, thereby appearing at multiple places in the node tree. The following illustrations show an example of a structure where an object (with an ID of 31) has multiple locations in the tree.
Objects, nodes and the content node tree - multiple locations
Content node tree with multiple locations
Main and secondary locations
When an object has multiple locations (and is thus associated with more than one node), only one node can be considered the main node of the object. The main node usually represents the object's original location in the tree - where it was first put. The other nodes can be thought of as additional or secondary nodes (or locations). Among other things, the main node is used to avoid duplicate search hits; a search result returns only main nodes.
The cross publishing feature only works with single nodes. If you add a new location for a folder that contains sub items (such as several news articles), the system will only make a new location for the folder itself - not the sub items. In other words, adding a location to a content object does not add locations to its children. Because of this, cross publishing is mainly used to add locations to standalone content such as articles, images and information pages.