> data types won't matter (hence XML doesn't have them, but after that JSON got them back)

JSON does not have very much or very good data types either, but (unlike XML) at least JSON has data types. ASN.1 has more data types (although standard ASN.1 lacks one data type that JSON has (key/value list), ASN.1X includes it), and if DER or another BER-related format is used then all types use the same framing, unlike JSON. One thing JSON lacks is octet string type, so instead you must use hex or base64, and must be converted after it has been read rather than during reading because it is not a proper binary data type.

> The funny thing about namespaces is that the prefix, by the XML docs, should be meaningless -- instead you should look at the URL of the namespace. It's like if we read a doc with snake:front-left-paw, and ask how come does a snake have paws? -- Because it's actually a bear -- see the definition of snake in the URL!

This is true of any format that you can import with your own names though, and since the names might otherwise conflict, it can also be necessary. This issue is not only XML (and JSON does not have namespaces at all, although some application formats that use it try to add them in some ways).