Inkscape XML Namespace
You have found this page because the inkscape svg document contains a URI like string which points here. This identifier is not an actual URL and doesn't contain any definition or other information about the type of information contained in the namespace.
What is a Namespace Name
The namespace name, to serve its intended purpose, SHOULD have the characteristics of uniqueness and persistence. It is not a goal that it be directly usable for retrieval of a schema (if any exists).
(…) namespace names are just strings, so the fact that the SVG namespace name also looks like a URI isn't important. URIs are commonly used because they are unique, the intention is not to "link" somewhere. (In fact URIs are used so frequently that the term "namespace URI" is commonly used instead of "namespace name".)