Depgraph uses a few terms that can be a little confusing at first, so let’s define them up front.

• Workspace - This is equivalent to a stored graph database instance. It’s the basic level of isolation between collections of relationships.
• View / ViewParams - Each workspace can have one or more views on the relationships stored within. Views are defined by:
  • a workspace …duh.
  • one or more “root” or top-level GAVs where any traversal (or graph discovery) begins
  • a filter which selects which relationships are included in any graph traversal
  • a set of selected versions which provide a way to guide the discovery of a relationship graph by pushing discovered GAV versions to use something else (like what a Maven BOM does)
  • a mutator which operates during a graph traverse, and under most circumstances uses the selected versions and any “managed” relationships up-path to manage GAV versions in successive path nodes (think of how Maven’s dependencyManagement influences transitive dependencies)
• Graph / RelationshipGraph - Interface combining a workspace and a view definition, and providing operations to work with the relationships that are available in that view.
• Filter - A class that determines whether a relationship belongs in the current view / traversal or not, and can construct a “child” filter based on itself to apply to successive nodes in a graph path (useful for resolving runtime dependencies of a plugin declared in a POM, for example)
• Traversal - A class that applies one or more filters to a RelationshipGraph and stores paths and/or nodes in order to arrive at some specific extraction from the graph. A Build Order traversal, for example, accumulates a partially ordered list of the GAVs in the graph.
• Node - a GAV stored in a graph, optionally augmented with metadata from the POM or elsewhere
• Relationship - an expression of one way that two GAVs are related, possibly with additional information specific to relationship according to its type

Why are there scare quotes on “root” (as in “root” GAVs)

Mathematically speaking, graphs don’t really have roots. And in reality, neither do project-relationship graphs. However, you do need to have some entry point in order to traverse (or discover!) a graph, and it seems simpler to think of these as roots. If you like, you could call them traversal roots, since that’s what they are. The quotes are just a way of acknowledging this potentially confusing situation.