Automatically resolve and index composition dependencies (and dependents?)

Subgraph composition introduces a new relationship type between data artifacts. Similar but different to how developers can graft a new subgraph onto an existing subgraph (unbounded depth), composition enables developers to re-use and extend data from one subgraph in another (1 layer deep max, but many subgraphs can use data from a single "core" subgraph).

The initial release of composition feature will expect Indexers to manual resolve and index composition relationships. Potential enhancements to streamline the Indexer experience might include:

• Automatically resolve and index composition dependencies
• Discovering children/dependent subgraphs
  • Automatically index composition dependents for a subgraph already indexed?

User validation is required on the latter enhancement, but Indexers (i.e. Pinax, StakeSquid) have already requested the former improvement.

Follow up with devs:

• enforce 1 layer deep
• enforce no grafting

No files, tests, or entry points are identified. Start by clarifying how composition dependencies and dependents should be discovered, resolved, and indexed, then confirm the one-layer and no-grafting constraints with developers and users. Done should include an agreed scope and validation for the requested Indexer automation.