# Dependency Graph
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When resolving transitive dependencies, Resolver (formerly Aether) constructs a *dependency graph*.
The graph contains `DependencyNode` instances.
Each node represents one dependency.
The direct dependencies of a node are its child nodes.
During the early stages of resolution, the graph usually contains duplicate dependencies and sometimes cycles.
The example below shows this.

```
   root
   / \
  /   \
a:1   b:1  <--+
  \   / \     |
   \ /   \    |
   c:1   a:2  |
    |         |
    +---------+
```

After conflict resolution, the graph becomes a *dependency tree*.
Conflict resolution removes duplicate dependencies.
The tree for the previous example looks like this:

```
   root
   / \
  /   \
a:1   b:1
 |
 |
c:1
```

The dependency tree is a useful data structure.
It provides the complete set of artifacts that are necessary to form a classpath.
A simple recursive traversal gathers the relevant dependencies.

## Troubleshooting a Dependency Graph

The dependency tree provides a basic way for end users to understand why and how a given artifact became a dependency.
But the dependency tree omits some information that the dependency graph has.
The examples above illustrate this.
For example, the tree does not show that `b:1` also depends on `c:1`.
To troubleshoot complex dependency graphs, some configuration properties keep useful data in the dependency graph returned by `RepositorySystem.collectDependencies()`.

For example, enable the configuration property `ConflictResolver.CONFIG_PROP_VERBOSE` to produce a graph similar to the dependency hierarchy view in m2e.
The graph keeps the nodes that conflict.
This helps end users understand all the paths that pull in a given dependency.

Enable the configuration property `DependencyManagerUtils.CONFIG_PROP_VERBOSE` to record the attributes of a dependency before the dependency manager modifies them.
This helps end users understand why the graph contains one version of a dependency instead of another.
It also helps them understand why a dependency is in a given scope.

The API documentation for these configuration properties describes their effects.
It also describes how to access the additional data.
