Generic Expression Hardness Results for Primitive Positive Formula Comparison. ## AbstractWe study the expression complexity of two basic problems involving the compar- ison of primitive positive formulas: equivalence and containment. In particular, we study the complexity of these problems relative to nite relational structures. We present two generic hardness results for the studied problems, and discuss evidence that they are optimal and yield, for each of the problems, a complexity trichotomy.
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