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Based on the geometrization of class structures , optimizing class structures in the feature space is equivalent to maximizing the quadratic quantities of metric tensors in the semi-Riemannian space .
 feature space, class structures; semi-Riemannian space, quadratic quantities of metric tensors
Please list all entity pairs containing a certain relationship in the given options.Output format is "word1, word2; word3, word4". 
Option: conjunction, feature of, hyponym of, used for, part of, compare, evaluate for 
Text: {0} 
Answer:
 feature space, class structures; semi-Riemannian space, quadratic quantities of metric tensors