XML Namespace ガイド
リファレンス 用 XML namespaces, prefix binding, および default namespace handling.
Namespace Basics
XML namespaces disambiguate element and attribute names by associating them with URIs. The xmlns attribute declares a default namespace; xmlns:prefix binds a prefix. Namespaces are URIs, not URLs; they need not be resolvable. The same local name in different namespaces are distinct elements. Namespaces enable mixing vocabularies (e.g., XHTML + SVG + MathML) in one document.
- xmlns
- Default namespace
- xmlns:prefix
- Prefix binding
- URI
- Identifier not address
no prefix neededns:elementneed not resolvePractical Issues
Default namespaces do not apply to attributes; attributes are unprefixed or use a prefix. Namespace prefixes are arbitrary; only the URI matters for identity. QNames in attribute values (e.g., xsi:type) require prefix-to-URI mapping. The XML Namespaces 1.1 spec allows undeclaring prefixes. Correct namespace handling is essential for schema validation and XPath/XSLT.
- attributes
- No default namespace
- QName
- Prefix in value
- identity
- URI matters, not prefix
must use prefixxsi:type="ns:Type"prefix is alias