An object which is representable as a collection of other objects may have a Folder Facet (Figure 4.7) which enables it to be displayed in a generic "folder" UI element.

Figure 4.7. The Folder and Column Facets.

A Folder provides a list of Column objects, each of which represents some property of all the elements of the Folder. The Columns can be used by UI elements to provide a tabular view of the contents of the Folder, and to sort the contents of the Folder based on the property represented by the Column.

Important

The FolderFacet should provide certain standard columns, exactly equivalent to the "standard properties" of Propertiess. For example, we would have methods getDisplayName(int) and getDisplayNameColumn().