As XML has become an emerging standard for information exchange on the World Wide Web, it has gained attention in database communities to extract information from XML seen as a database model. Recently, many researchers have addressed the problem of storing XML data and processing XML queries using traditional database engines. Here, most of them have used relational database systems, while we show in this paper that object-oriented database systems can be another solution. Our technique generates an OODB schema from DTDs and processes XML queries. In particular, we show that the semi-structural part of XML data can be represented by ‘inheritance’ and that it can be used to improve query processing.