Take a presentation and export it to svg. The document will start as
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg version="1.2" viewBox="0 0 28000 21000" preserveAspectRatio="xMidYMid" fill-rule="evenodd" stroke-width="28.222" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg" xmlns:ooo="http://xml.openoffice.org/svg/export" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:presentation="http://sun.com/xmlns/staroffice/presentation" xmlns:smil="http://www.w3.org/2001/SMIL20/" xmlns:anim="urn:oasis:names:tc:opendocument:xmlns:animation:1.0" xml:space="preserve">
Notice that the version as attribute in the <svg> element is said to be 1.2, but the DOCTYPE is for 1.1
The version 1.2 only exists as "SVG Tiny 1.2". It has intentionally no DOCTYPE at all, but you have to use the attribute baseProfile="tiny",
Or if the DOCTYPE is intentionally used, than the version attribute needs to have the same version and only SVG1.1 features may be used.