6.1.1 and elsewhere we rely on "document order" but don't define it.

The term "document order" is used at 6.1.1, 6.1.2, 7.4.1, 8.1.1, 9.1.5, 9.2.7, and 16.29.7.

However, we never define it.

I am partial to the XPath 1.0 definition:

"There is an ordering, document order, defined on all the nodes in the document corresponding to the order in which the first character of the XML representation of each node occurs in the XML representation of the document after expansion of general entities. Thus, the root node will be the first node. Element nodes occur before their children. Thus, document order orders element nodes in order of the occurrence of their start-tag in the XML (after expansion of entities). The attribute nodes and namespace nodes of an element occur before the children of the element. The namespace nodes are defined to occur before the attribute nodes. The relative order of namespace nodes is implementation-dependent. The relative order of attribute nodes is implementation-dependent. Reverse document order is the reverse of document order."

as opposed to the overly clever XPath 2.0 definition that is more confusing than helpful.