The resource /deployment=*/subsystem=web should contain an attribute "url" which contains the resolved absolute url to the web deployment.

The resource does contain the attribute "context-root". But this only provides a relative url. To make this absolute additional resource operations are necessary (like parsing interfaces, port offsets, ...)

By having an absolute url the user can quickly access the deployment:
1. By copy/paste into the browser (when using the cli)
2. By following a hyperlink (when using the admin console)

As an example the resources for webservice endpoints already contain an absolute url to the WSDL. This is used in the admin console to provide a hyperlink (see AS7-2152)