In the Appendix there should be an index of technical terms that are not part of the language, such as “scope”, “binding”, “compilation unit”, “constructor”, “type constructor”, “class function” (as in the explanation of “Class application” in section 6.9.2), “compatibility of types” (as in “This type is still compatible with a variant type containing more tags.” in “Variant types” in section 6.4) etc. (The index of meta-concepts) The syntactic categories should be included or put in their own index.