The  Directed E/R Graph domain defines the top level constructs of entity (Entity Element) and their relationships (Relationship Element).

It is the second layer of  SysFEAT's graph architecture.

 SysFEAT is based on a node-centric definition of graphs, aligned with practical implementations like adjacency lists in programming

To leverage graph defintions,  SysFEAT has adopted a layered approach of relationship formalization:

1) It starts by explicitly encoding directed edges as set-based constructs: Adjacency List.

2) Adjacency Lists are then reified to create direct relationships between Relationship Elements: Relationship Elements.

3) Further structuring of Entity Elements and their Relationship Elements is provided by the Compositionality pattern that layouts the concepts of locality and connections.