A graph-oriented object database model (GOOD) is introduced as a theor
etical basis for database systems in which manipulation as well as con
ceptual representation of data is transparently graph-based. In the GO
OD model, the scheme as well as the instance of an object database is
represented by a graph, and the data manipulation is expressed by grap
h transformations. These graph transformations are described using fiv
e basic operations and a method construct, all with a natural semantic
s. The basic operations add and delete objects and edges in function o
f the matchings of a pattern. The expressiveness of the model in terms
of object-oriented modeling and data manipulation power is investigat
ed.