Quiz Entry - updated: 2026.07.30
Oracles are classified along two foundational dimensions in this pattern framework. What are they?
Direction (inbound vs outbound) and initiator (pull vs push) — a 2×2 that yields four foundational oracle patterns.
The whole taxonomy collapses to two independent questions:
| Dimension | Options | What it asks |
|---|---|---|
| Direction | inbound / outbound | Which way does the data flow, seen from the blockchain? |
| Initiator | pull / push | Who starts the exchange — the receiver requesting, or the sender volunteering? |
Crossing them gives four patterns: pull-based inbound, push-based inbound, pull-based outbound, push-based outbound. A useful property of this abstraction is that it doesn't depend on smart contracts — the patterns can be implemented even on a first-generation chain like Bitcoin.
Go deeper:
Foundational Oracle Patterns (Mühlberger et al., arXiv) — the source of the direction × initiator taxonomy and the four patterns it yields.