From NSDLWiki

hasResourceURL

The hasResourceURL property denotes the URL of a resource.

Namespace 

http://ns.nsdl.org/api/relationships#

Prefix 

nsdl

Cardinality 

exactly one

Found in 

Resource

Values 

A valid URL.

Usage and Semantics

• The url contained in this property will ultimately resolve to the same content contained in the Content datastream.
• When editing a resource, either the content datastream or hasResourceURL property needs to be specified, but not both:
  • For primary content, the NDR will automatically provide an appropriate value for this property to point to the content datastream, which overrides any value provided by the user.
  • For resources that reference external resources, the NDR will automatically keep the content datastream in sync with the specified URL.
• The value for this property is unique repository-wide.