"Attribute indicating what types of content can be dropped on an element."
tagged("enumerated attribute")
shared class DropZone 
        of copy | move | link 
        satisfies AttributeValueProvider {
    shared actual String attributeValue;
    "Indicates that dropping will create a copy of the element that was dragged."
    shared new copy {
        attributeValue = "copy";
    "Indicates that the element that was dragged will be moved to this new location."
    shared new move {
        attributeValue = "move";
    "Create a link to the dragged data."
    shared new link {
        attributeValue = "link";