[tannhaeuser]

XML namespaces were controversial when introduced, and their implementation as privileged "xmlns:..." attributes with complex scoping, layering, and defaulting rules have been criticized many times; see [1] for a reflection from 2010 by an insider admitting to the fact that "every step on the process that led to the current situation with XML Namespaces seems reasonable".

When in 1996-98 W3C/The SGML Extended Review Board subset XML from SGML to define a generic markup convention for use with the expected wealth of upcoming vocabularies on the web, the issue of name collisions between elements (and attributes) from different vocabularies was deemed significant. Of course, in hindsight, with only SVG and MathML (and rarely HTML 5 in XHTML serialization) left on the web and having been incorporated as foreign elements directly into HTML, this seems overkill (even though there are actually collisions between eg. the title element in SVG vs HTML).

There's an alternative (and saner IMHO) approach for dealing with XML namespaces in ISO/IEC 19757-9 [2] by just presenting a canonical (ie. always the same) namespace prefix as part of an element name by a parser API to an app, guided by processing instructions for binding canonical namespace prefixes to namespace URLs, which might also help enterprise-y XML with lots of XML Schema use. Of course, this doesn't help with roundtripping xmlns-bindings (eg. with their exact ordering, possible redundancy, temporary/insignificant namespace prefixes, re-binding in document fragments etc.) through DOM representations, which seems the problem here.

[1]: https://blog.jclark.com/2010/01/xml-namespaces.html

[2]: https://www.iso.org/obp/ui/#iso:std:iso-iec:19757:-9:ed-1:v1...