This article explains why XML format has become established as the standard format for multilevel hierarchical structuring of linguistic databases and how an XML Schema can be used to manage the formal structure and content of elements in a dictionary database. Various aspects that must be taken into account when structuring complex dictionary databases in XML format are presented: the lexicographic or content aspect, the practical aspect, and the technical aspect. Decision-making is illustrated with the example of designing an XML Schema for the Dictionary of Slovenian Synonyms.