In this paper we describe a data model called GROOVY
(Graphically-Represented Object-Oriented data model with Values) whose
graphical representation provides a simple unifying formalism for the main
concepts of object-oriented data modelling.  In GROOVY, real-world entities
are represented by means of objects over object schemas.  Object schemas
include integrity constraints which are an extension of the functional
dependencies of relational database theory, allowing both single-valued and
multi-valued functions.  Object schemas have a multi-level structure and
allow for the encapsulation of information.  We show that the representation
of object schemas by means of hypergraphs leads to a natural formalisation
of the notions of sub-object sharing and structural inheritance while also
providing a simple interface suitable for user interaction.  We also show
how objects over object schemas can be represented by hypergraphs labelled
with object identifiers.  By considering equivalence classes of isomorphic
hypergraphs, a value-oriented sub-model of GROOVY is obtained.  Finally, we
present the necessary primitives for a procedural hypergraph query and
update language. <P>

GROOVY was the forerunner of the Hypernode Model.