Content Views can be linked to a document type by specifying the content view names in its definition.
Some default document views present content views for listing this folderish document content, for instance, or to present the result of a search using some of the document properties as parameters (like in the Smart Search addon).
A category has been added to make the distinction between the different views, here is a sample configuration:
<type id="Workspace">
[...]
<contentViews category="content">
<contentView>document_content</contentView>
</contentViews>
<contentViews category="trash_content">
<contentView showInExportView="false">
document_trash_content
</contentView>
</contentViews>
</type>
The category content is looked up by the default tab showing a folderish document content. The category trash_content is looked up by the default tab showing a folderish document trash content.
Several content views can be shown on each of these views.