The order Attribute
Definition of the Recently Introduced order Attribute
3.1.4. order = ( document | list )
The order attribute indicates how this access element should determine the navigation order for its matching elements. The default value, document, indicates that the items MUST be traversed in document order. The alternate value, list, indicates that the navigation order of matching elements is determined by the author-defined order of items in the list of targetid or targetrole attribute values.
For the sake of determining navigation order, elements in the document that match the values in the targetid or targetrole attributes are called matching elements, and all elements that match the same value are members of an element group. Note: since the id of an element must be unique within a valid XML document, in such documents, each element group based on targetid values consist of no more than one matching element.
For each navigation operation, the navigation order for both document-order and list-order is sensitive to the current focus element. For document-order, if no element currently has focus, the first matching element in the document MUST be the focus target; if an element does have focus, the next matching element in the document MUST be the focus target. For list-order, the focus target navigation order is determined as follows:
If no matching element of this access element currently has focus, the focus target MUST be the first element in document order that matches the first element group. If there is no such element, then the focus target is the first element that matches the second element group, and so on.
If a matching element of this access element already has focus:
If there are additional matching elements of the same element group in document order, then focus MUST be sent to the next matching element of the same element group.
Otherwise, focus MUST go to the first matching element (in document order) of the next element group.
If there are no remaining element groups, then the search MUST resume from the first element group.
The location of the next matching element MUST be determined each time the access element is triggered, since it is possible that between events the contents of the document will have changed.