xml

Namespaces

• XPath /root/child fails if document has default namespace—use //*[local-name()='child'] or register prefix
• Default namespace (xmlns="...") applies to elements, not attributes—attributes need explicit prefix
• Namespace prefix is arbitrary—<foo:element> and <bar:element> are identical if both prefixes map to same URI
• Child elements don't inherit parent's prefixed namespace—each must declare or use prefix explicitly

Encoding

• <?xml version="1.0" encoding="UTF-8"?> must match actual file encoding—mismatch corrupts non-ASCII
• Encoding declaration must be first thing in file—no whitespace or BOM before it (except UTF-8 BOM allowed)
• Default encoding is UTF-8 if declaration omitted—but explicit is safer across parsers

Escaping & CDATA

• Five entities always escape in text: & < > " '
• CDATA sections <![CDATA[...]]> for blocks with many special chars—but ]]> inside CDATA breaks it
• Attribute values: use " if delimited by ", or ' if delimited by '
• Numeric entities < and < work everywhere—useful for edge cases