The orderable child nodes setting is defined per node type. Whether the child nodes of a node N are orderable depends on the node type of N.
A repository supports orderable child nodes by permitting the registration of node types with an orderable child node setting of true.
When a node does not support orderable child nodes this means that it is left up to the implementation to maintain the order of child nodes. Applications should not, in this case, depend on the order of child nodes returned by Node.getNodes, as it may change at any time. The only exception to this rule is that same-name siblings must maintain their relative order across read method invocations and across sessions.