xmlns ↔ a
xmlns="http://www.w3.org/2000/svg"
Required for image/svg+xml files. Optional for inlined <svg>. 2
xmlns:xlink="http://www.w3.org/1999/xlink"
Required for image/svg+xml files with xlink: attributes. 1
Optional for inlined <svg\> with xlink: attributes.
version="1.1"
Recommended to comply with image/svg+xml files standards. ignored by every user agent. Removed in SVG 2. 5