@inproceedings{conf/sdb/GottlobKS95,
  title = "The Evolving Algebra Semantics of Class and Role Hierarchies",
  author = "Georg Gottlob and Gerti Kappel and Michael Schrefl",
  year = "1995",
  booktitle = "{Semantics in Databases, Selected Papers from a Workshop, Prague, Czech Republic, 1995}",
  editor = "Leonid Libkin and Bernhard Thalheim",
  isbn = "3-540-64199-8",
  pages = "92-113",
  publisher = "Springer",
  series = "Lecture Notes in Computer Science",
  volume = "1358",
}