URIStringtype

Valid URI string is anything following protocol:resource format, e.g. urn:isbn:0451450523 or http://example.com/path/to/resource

URI and URL differences:

• According to RFC 3986, URLs are a subset of URIs that have a hierarchical path component, e.g. http://example.com/path.
• The // at the start of a URL indicates that it has a hierarchical path component, so this makes it a URL.
• The absence of // indicates a non-hierarchical URI.
• URLs can be considered as "hierarchical URIs".
• All URLs are also URIs, but not all URIs are URLs.