PROGRES supports structurally object-oriented specification

of attributed graph structures with multiple inheritance

hierarchies and types of types (for parametricpolymorphism). It also supports declarative/relational

specification of derived attributes, node sets, binary

relationships (directed edges) and Boolean constraints,

rule-oriented/visual specification of parameterised graph

rewrite rules with complex application conditions,

nondeterministic and imperative programming of composite

graph transformations (with built-in backtracking and

cancelling arbitrary sequences of failing graph

modifications).