research: temporal graph traversals (temporal network analysis) #273

Background

The RecallGraph temporal query taxonomy notes in its appendix that temporal graph traversals (temporal network analysis) are a distinct class of query beyond the four standard temporal query classes (point-in-time, time-interval, time-point lookup, time-interval lookup).

These are traversal queries where the graph topology itself changes over time — e.g., "what paths existed between A and B during the interval [t1, t2]?" or "which nodes were connected at both t1 and t2?".

This is an active research area; see the Wikipedia article on temporal networks for an overview of the emerging patterns.

Current state

Minigraf's bi-temporal model stores the full history of edge assertions and retractions. Time-aware traversal is possible today by combining recursive Datalog rules with :as-of / :valid-at qualifiers — but this requires the user to structure their queries carefully and does not provide dedicated temporal traversal operators.

Work item

Research whether dedicated temporal traversal operators (e.g., time-constrained reachability, temporally-consistent path queries) belong in Minigraf's Datalog dialect, and if so, what syntax and semantics would fit the existing query model.

Acceptance criteria

• Survey the literature on temporal graph traversal query classes.
• Assess which patterns are expressible today via recursive rules + temporal qualifiers, and which are not.
• Propose candidate syntax and semantics for any new operators, assessed against PHILOSOPHY.md.
• Produce a design doc or a decision record (defer/won't-do if the complexity outweighs the value).

Notes

• Surfaced as out-of-scope during cookbook design (issue post-1.0: write cookbook for common query patterns #190).
• Milestone 2.0 — do not implement before the research phase is complete.