Is curled quote valid xml for attribute value

Question

For example is the following line a valid xml

<?xml version=“1.0” encoding=“UTF-8” ?>

It would be very helpful if somebody also able to provide reference for this.

Answer 1

As for the reference, the XML specification is at https://www.w3.org/TR/REC-xml/ and the relevant rule is

[10]    AttValue       ::=      
           '"' ([^<&"] | Reference)* '"'
        |  "'" ([^<&'] | Reference)* "'"