1. A database system for storing data including Extensible Markup Language (XML) instances, said database system comprising: a computer processor; and a computer readable storage medium having a tangible physical structure, the tangible medium having program code that causes said processor to perform a plurality of operations, said operations comprising: generating an XML schema collections container in a relational database for collecting a plurality of XML schema namespace universal resource identifiers (URIs), each namespace URI respectively identifying a single collection of element types and attribute names in an XML instance that corresponds to a location typed XML schema document wherein, the XML schema document defines the namespace URIs in the container and a set of attributes, relationships, organizations, and functions for confirming with the XML instance; and each namespace URI in the container allows a reference to any XML schema document in the system; placing in the created container at least two XML schema namespace universal resource identifiers (URIs) which represent at least two different location typed SQL server namespace schemas in the relational database; validating a single complex namespace schema for a redefined XML instance by calling an import function specified in the redefined XML instance with at least one of the two location typed schemas that were placed in the container by the respective URIs; associating a column of a table in another database with the XML schema collections container prior to the validating operation, by setting the location type of the column in the table of the other database in context of the single complex namespace schema for the redefined XML instance, with any other XML schemas being placed in the container when referencing respective URLs; and storing the validated single complex name space schema for the redefined XML instance within the column of the container when invoking an alter XML schema collection function specified by the redefined XML instance that adds the validated single complex name space schema for the redefined XML instance into the column of the container in a form of the location typed URI.