@article {ART-1990-01,
   author = {Frank Leymann},
   title = {{UDH: A Universal Relation System}},
   journal = {Data \& Knowledge Engineering},
   address = {Amsterdam, The Netherlands},
   publisher = {Elsevier Science Publishers B. V.},
   volume = {5},
   number = {1},
   pages = {21--38},
   type = {Article in Journal},
   month = {March},
   year = {1990},
   issn = {0169-023X},
   doi = {10.1016/0169-023X(90)90031-8},
   keywords = {Relational database; Universal relation; Database semantic; Access path; Data model; Query language; Database navigation; Window; Object scheme; Database handler; Design Implementation; Data manipulation},
   language = {English},
   cr-category = {H.2 Database Management,
                   H.2.1 Database Management Logical Design,
                   H.2.3 Database Management Languages},
   department = {University of Stuttgart, Institute of Architecture of Application Systems, Architecture of Application Systems},
   abstract = {The concept of a new universal relation system, called UDH (unified database
      handler), is given, allowing enquiries of relational databases without
      references to the underlying database scheme. Also, UDH attempts to decouple
      data manipulation requests from the database scheme via an additional layer
      above the database scheme, called semantic object scheme.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-1990-01&engl=1}
}