1 Introduction

"The primary purpose of XPath is to address the nodes of [XML 1.0] or [XML 1.1] trees."

Ahem, Neither XML 1.0 (Fifth Edition), http://www.w3.org/TR/REC-xml/ and XML 1.1 (2nd Edition), http://www.w3.org/TR/xml11/ define trees. In 4.8 Document Entity they both define "The document entity serves as the root of the entity tree..." and in Deterministic Content Models (E in 1.0, F in 1.1) they both refer to "...each leaf node in the syntax tree...."

I assume this was meant informally in the introduction so no normative reference is required and it can simply say: "address the nodes of XML trees."