Marks if the row is virtual and behavior of getPath is undefined. The implementation may
choose to return null or empty string. User of a virtual row should now rely of value of
getPath returned from virtual rows.
The value of the given property, if available. This might be a property
of the given node, or a pseudo-property (a property that is only
available in the index but not in the node itself, such as "jcr:score").