Attributes „Approximate“ and „Valid“

Hi,
As far as I understand, the Approximate attribute is set if the server requests a LBS geolocation. Is it set with the request or with the valid answer to the request, I.e. if a location was returned.
How do LBS requests and answers influence the Valid attribute? Is it set to Valid, even if the tracker reports an invalid position (I.e. no GPS fixing) and the LBS geolocation request succeeds?
Sorry, if there is a description of this and I missed that.
Thank you in advance!