Metadata view
From OpenKM Documentation
Metadata view is a hierarchical tree structure of metadata groups ( property groups ). Each possible metadata value is represented as a tree node structure.
A document, folder or mail can be linked with many metadata property values folders at the same time. Each time some metadata value folder is selected, all related documents, folders or mails will be displayed in the file browser panel. All the major document, folder or mail functionalities are available from this view.