A group identifier represents an association between each of a number of different abbreviated namespace identifiers with a corresponding hierarchical namespace (e.g., an XML namespace). A hierarchically-structured document (e.g., an XML document) is accessed by a computing system that determines that the group identifier is associated with the hierarchically-structured document. Hence, when using the abbreviated namespace identifiers in the hierarchically-structured document, the computing system knows that the corresponding namespace is associated with the designated portions of the hierarchically-structured document. Also, a schema description language document (e.g., an XSD document) may specify multiple target namespaces for a single element. Accordingly, groupings of elements may be included in different namespaces to creating overlapping or even nested namespaces.