A directed acyclic graph (DAG) is a directed graph with no cycles: following its arrows can never return to the starting node. It represents one-way relationships. section 1.2.2
Use DAGs when relationships must flow without looping:
- Model causal structures in which A can cause B, but B cannot simultaneously cause A. section 1.2.2
- Represent workflow processes and dependency chains whose steps proceed in one direction. section 1.2.2
- Distinguish a DAG from an undirected acyclic graph: DAG edges are directed, while an acyclic graph may be undirected. section 1.2.2
Following a one-way path
In the illustrated DAG, directed edges flow from A toward F. Unlike the cyclic example, no sequence of arrows leads back to its starting node.














