The type of data in the working list
In an unlevelled list, the data includes a unique ID for each item as well as the id of the item's parent. This type of list can be used to build a whole tree or it can be used to build an Ajax tree. In an Ajax tree the initial list contains a subset of the full tree (at least the visible items, possibly some sublevels). When the user attempts to open a branch that has no children the TreeView will execute a webrouting to obtain a new copy of the list containing new items to add to the tree.
Items in the TreeView will be created in list order. So, the items in the unlevelled list must be sorted such that parents occur before their children and children of a single parent occur in display order.
In a levelled list the TreeView infers the tree structure from the data. You provide the Tree View a list of column names (known as key fields) to use for folders and it automatically builds the tree structure by grouping items with the same key value under the same parent. The Tree View does this grouping by comparing the key fields of each entry with the key fields of the previous entry. It is your responsibility to ensure the list is correctly sorted into display order.
'levelled' or 'unlevelled'.