What is the relationship between FACS and an emotion-reading tool?

Answer

FACS is an anatomical map describing movements, not an emotion-reading tool itself.

FACS is an objective descriptive system detailing muscle movements (AUs); it provides the language to describe what the face is doing without interpreting the emotion or 'why' it is being done.

What is the relationship between FACS and an emotion-reading tool?
inventiontechnologyrecognitionpsychologyemotion