The Research on XML database systems is mainly focused on the following six aspects:
1) Research on the XML data query model, query language, and query algebra;
2) study the XML data encoding scheme and index structure;
3) studies pure XML database systems, including storage structure, indexing technology, query technology, and transaction management;
4) Research on Relational XML databases, including the relational storage mode, XML query technology and query algorithm of XML data, and the technology for publishing relational data in XML documents, use middleware to query relational data in XML format and XML query language and integrate information of heterogeneous data sources;
5) XML query technology, query algorithm, and XML query inclusion and equivalence, tree-mode query minimization, and query optimization technology;
6) Conduct research on the XML query test dataset and test query example.