XML namespace declared with no prefix, for example, `xmlns="some-uri-here"`.
xml-namespaces declared with no prefix, for example, xmlns="some-uri-here"
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Default namespace applied implicitly to elements without prefix (unprefixed elements?) i.e when default namespace declared in an unprefixed element, then that element is considered in the default namespace. Descendant elements without prefix also inherits default namespace from its ancestor. In case of multiple default namespace found among ancestor elements, default namespace from the nearest ancestor is applied.
This tag was created originally because many questions, in various programming language and platform, has been asked where the root cause of OP's confusion is the same: existence of default namespace. But even so, whenever new question comes, it isn't easy to find a good older duplicate question.