Multiple views of nested provenance

[ChrisKeefe]

QIIME 2's provenance capture supports multiple views of provenance graphs. Under the hood, Pipelines run other Actions, possibly including Pipelines. Provenance is captured for each inner-Action result, and a redundant terminal result (an alias) is also recorded for the pipeline itself, allowing tools like q2view to hide inner Actions. For details, see the dev docs.

We should expose at least two (and probably three) views of provenance:

• [x] Complete: all Results are visible, including aliases, because it's easy and allows interfaces to make their own choices
• [x] Nested: like q2view, where inner nodes are hidden behind terminal/alias nodes
• [ ] Inner Actions: terminal nodes are hidden, showing a comprehensive collection of Actions performed

[ChrisKeefe]

A valid solution should:

• expose at least complete and nested views
• allow users to interact with multiple views without re-generating the ProvDAG

NetworkX prefers graphviews to approaches that add/remove nodes or edges. subgraph_view is the right play.

[ChrisKeefe]

blocked by #25

[ChrisKeefe]

Closing for now. Can reopen in future if Inner Actions seems like a useful view