In  this  paper we  present  some of  the  results achieved  while  realizing an
international  research  project aiming  at  the design  and  development of  an
Object-Relational Data Warehousing System (ORDAWA). The most important goals  of
the project are  as follows: the  development of techniques  for the integration
and consolidation  of different  external data  sources in  an object-relational
data warehouse, the construction  and maintenance of materialized  relational as
well as  objectoriented views,  and the  development of  techniques allowing  to
modify the schema of a data warehouse when
data sources change their schemas.