Levels of hierarchy can be mailboxes.Logical formLearned from2 sentences. A level can be constituted-of-or-filled-with (mailbox hierarchy).Logical formLearned from2 sentences. A (hierarchy separator character) may be used for some levels of hierarchy.Logical formLearned from2 sentences. A hierarchy may correspond to a (naming hierarchy).Logical formLearned from2 sentences. A (domain hierarchy) may pertain-to a country.Logical formLearned from2 sentences. A level can be in a (domain hierarchy).Logical formLearned from2 sentences. A hierarchy may contain a set of some domains.Logical formLearned from2 sentences. A domain can be at a top of a hierarchy.Logical formLearned from2 sentences. An existence of domains may impose a hierarchy.Logical formLearned from2 sentences. An arrangement may imply a hierarchy of servers.Logical formLearned from2 sentences. A directory-service may follow hierarchies.Logical formLearned from2 sentences. A (naming hierarchy) may be structured.Logical formLearned from2 sentences. A root can be for a (naming hierarchy).Logical formLearned from2 sentences. Some higher level can be in a hierarchy.Logical formLearned from2 sentences. Division can be within a hierarchy.Logical formLearned from2 sentences.