In Section 2.2.1, in the green rectangle for formal definitions, it is said: "We define a basic graph pattern for a model" -> I think it would be clearer to say "We define a basic graph pattern for a data model".
Since it only applies specifically to graph data models, extended the suggestion a bit: "We define a basic graph pattern for a particular graph data model".
In Section 2.2.1, in the green rectangle for formal definitions, it is said: "We define a basic graph pattern for a model" -> I think it would be clearer to say "We define a basic graph pattern for a data model".