core + attic (Attic Area): these terms have been either deprecated from the core or extentions, or removed from pending as not accepted into the full vocabulary.

proficiencyLevel

Canonical URL: http://schema.org/proficiencyLevel

Thing > Property > proficiencyLevel

Proficiency needed for this content; expected values: 'Beginner', 'Expert'.

Usage: Between 10 and 100 domains
Values expected to be one of these types
Text
Used on these types
TechArticle

Schema Version 3.3