A "profile type" is specified to describe the type of vocabulary being expressed; different features of the VDEX model are permitted depending on the profile type, providing a common grammar for several classes of vocabulary. For example, it is possible, in some profile types, for terms to be contained within one another and be nested, which is suited to the expression of hierarchical vocabularies. Five profile types exist: "lax", "thesaurus", "hierarchicalTokenTerms", ‘glossaryOrDictionary’ and "flatTokenTerms". The lax profile is the least restrictive and offers the full VDEX model, whereas the flatTokenTerms profile is the most restrictive and lightweight.