This paper describes a system that integrates full-text searching and datab
ase technologies for storing XML (eXtensible Markup Language) documents and
retrieving information from them while providing a uniform interface. Our
main goal with this system is to achieve high-performance, because there wi
ll be a large amount of XML documents in the near future if XML becomes a s
tandard for structured documents and data exchange. We have therefore devel
oped techniques for achieving highperformance storage and retrieval of XML
documents. For full-text searches, we improved the Structure Index + Text I
ndex model, which references both indexes alternately at retrieval. In our
improved method, a hieriarchical structure query is converted into a flat s
tructure query by referencing just the structure index, then the optimized
query can be quickly processed using only the text index. For storage, we d
eveloped an offset space, which is an address space in secondary memory tha
t can compactly store any structure, for example, a tree. We use the offset
space to solve the problem that occurs in other methods which store the an
alyzed result of XML documents as multiple relations in an nos. In our meth
od, the analyzed result can be stored in a single page in the best case. Th
is makes it superior to other methods which store the analysis results in m
ultiple relations so that storage of N relations needs at least N pages. As
a result, generally, our method greatly reduces I/O costs.