Attribute syntax:
[12] Attribute ::= NSAttName Eq AttValue | QName Eq AttValue
examples:
<a xmlns="http://www.w3.org/1999/xhtml" href='http://www.w3.org/1999/xhtml'/>
In the above, the first is a namespace declaration attribute and the second is a regular attribute.
The contents must be in a quoted literal so there are syntax constraints -- see next few slides.