[support] Drupal 7 workflows

[Roger]

With Configuration>Rules > Editing reaction Rule
Is there an explanation for the Data Selector and associated error 
messages such as:
The integrity check failed with the following error message: "Data 
selector /node:author:roles:/ for parameter /account/ is invalid."
There seems to be no hint or clue how to use this tool?
Can someone throw some light on Rules please, it may be that it would 
solve the workflow previously asked about.
Thanks in advance
Roger
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