The  Elementary Graph domain defines the basic constructs for relating and classifying Elements in a directed graph.

 SysFEAT is based on a node-centric definition of graph that follows the principal of lexical locality.

It defines the concepts of entity (Entity) and relationship (Relationship) as specific kinds of nodes.

To implement the principle of locality in graph definitions,  SysFEAT has adopted a layered approach of relationship formalization:
1) It starts by explicitly encoding directed edges as Kuratowski pair ,  <a,b> = { {a}, {a,b} }, represented as: Kuratowski's ordered pair.

2) Kuratowski's ordered pairs are then reified to create direct relationships between Entitys: Relationships.

3) Further structuring of Entitys and their Relationships is provided by the Compositionality pattern that layouts the concepts of dynamic locality and connections.