  Property graph manages data by vertices and edges. Each vertex and edge can
have a property map, storing ad hoc attribute and its value. Label can be
attached to vertices and edges to group them. While this schema-less
methodology is very flexible for data evolvement and for managing explosive
graph element, it has two shortcomings-- 1) data dependency 2) less
compression. Both problems can be solved by a schema based approach. In this
paper, a type system used to model property graph is defined. Based on the type
system, the associated data definition language (DDL) is proposed and multiple
graph instances created under this type system is discussed.
