First you need to define Virtual Resource.
Virtual Resources specifies a desired state for a resource without necessarily enforcing that state. Although virtual resources can only be declared once, they can be realized any number of times.
I will suggest you to mention the uses of Virtual Resources as well:
• Resources whose management depends on at least one of multiple conditions being met.
• Overlapping sets of resources which might be needed by any number of classes.
• Resources which should only be managed if multiple cross-class conditions are met.
