In Figure 8-1, there is an association directly between the stereotypes ComparisonOperator and OperatorSemantics. The intent seems to be for a stereotyped literal string to provide the name of the comparison operator associated with an operator semantics class. However, while such an association between stereotypes is technically legal syntactically (because stereotypes are kinds of classes), there is no standard way to instantiate it, because the standard does not require a tool to implement stereotyping using actual stereotype instances.
An alternative would be to associate the OperatorSemantics stereotype directly to LiteralString, requiring that the LiteralString be stereotyped by ComparisonOperator. However, this seems unnecessarily heavyweight. Instead, it would be much simpler to simply give OperatorSemantics a symbol: String property and move the applyTo operation to OperatorSemantics. The ComparisonOperator stereotype would then be entirely unnecessary.