Clarify URI vs URL as data type

[ValentinFutterer]

E.g. in distribution, the access_url and download_url have the data type URI. But they have URL in their name and they are obviously supposed to be links that lead to a webpage/download. In my opinion, URI is the wrong data type here, since URIs could either be a URl or a URN. URNs are just a unique name, with no way to access the resource behind the name. As opposed to URLs, which do offer a way to access the resource described. So in short, every URL is a URI, but not all URIs are URLs.

This ambiguity also affects other parts of the schema. As a software developer, I would like clarification on this issue, to validate inputs correctly.

[MarekSuchanek]

For reference e.g.: https://www.w3.org/TR/vocab-dcat-3/#Property:distribution_download_url

[MarekSuchanek]

OK, so all URI appearances as Data Type in the specs shall be changed to URL (in the README).

Is there also any change needed in the JSON schemas? For instance: https://github.com/RDA-DMP-Common/RDA-DMP-Common-Standard/blob/master/examples/JSON/JSON-schema/1.1/maDMP-schema-1.1.json#L329