"the child axis contains the children of the context node, which are the nodes returned by the dm:children accessor in [XQuery and XPath Data Model (XDM) 3.1]."

Correct URL: http://www.w3.org/TR/xpath-datamodel-31/#dm-children 5.3 children Accessor

"the parent axis contains the sequence returned by the dm:parent accessor in [XQuery and XPath Data Model (XDM) 3.1],"

Correct URL: http://www.w3.org/TR/xpath-datamodel-31/#dm-parent 5.11 parent Accessor

"the attribute axis contains the attributes of the context node, which are the nodes returned by the dm:attributes accessor in [XQuery and XPath Data Model (XDM) 3.1]; the axis will be empty unless the context node is an element"

Correct URL: http://www.w3.org/TR/xpath-datamodel-31/#dm-attributes  5.1 attributes Accessor

"the namespace axis contains the namespace nodes of the context node, which are the nodes returned by the dm:namespace-nodes accessor in [XQuery and XPath Data Model (XDM) 3.1];"

Correct URL: http://www.w3.org/TR/xpath-datamodel-31/#dm-namespace-nodes  5.7 namespace-nodes Accessor

"should use the functions fn:in-scope-prefixes and fn:namespace-uri-for-prefix defined in [XQuery and XPath Functions and Operators 3.1]."

Correct URLs:

http://www.w3.org/TR/xpath-functions-31/#func-in-scope-prefixes 10.2.6 fn:in-scope-prefixes

http://www.w3.org/TR/xpath-functions-31/#func-namespace-uri-for-prefix  10.2.5 fn:namespace-uri-for-prefix

I combined all of these in a single report since they fell under the same section. 

The suggested references have the advantage of using language that appears in the referenced text.