Glossary

Accumulation Buffer. Bounds on the base asset set aside for accumulation, configured as a [min, max] range and resolved live from the Fear & Greed index. Applies on every venue.

Alpha. The excess return generated by an investment relative to a benchmark index. In Dio, alpha refers to the profit earned from capturing market volatility beyond passive holding returns.

Action Library. The registry of named operations a strategy file may call. Each action declares its kind (decision, effectful, or read) and a schema the strategy is validated against; an unknown action name is a compile error. The library is the engine's only code-side extension point: a new capability is added by registering an action, and every strategy file can then call it.

Asset Agnostic. Operating identically regardless of the underlying traded asset. The oracle derives its references from each asset's own price history, so equities, bonds, ETFs, options, futures, FX, and digital assets are all handled the same way.

Capital Oracle. The engine's sizing layer. It merges each asset's all-time price history, derives drawdown references from it, verifies candidate parameters by survival replay, allocates quote pools per venue in priority order, and publishes one decision record per asset.

Cancellation Cascade. The mechanism by which a higher-priority strategy's unaffordable need cancels lower-priority resting buys until capital frees up. Many lesser orders may be cancelled to satisfy one greater; cancelled strategies re-evaluate on the same event.

Copy-On-Write Map. A hash map split across a fixed number of shards, where each shard is an immutable map published through its own atomic variable. A lookup reads one shard and allocates nothing. A write copies only the shard it lands in and replaces that one variable, so the copy is proportional to a shard. Readers never take a lock and never observe a half-updated table, which makes the map safe to read from many trading domains while another writes to it. Instrument metadata, the per-venue feed store registries, and the per-symbol lifecycle-event queues are all built this way.

d_surv. The survival fraction produced by replaying candidate ladder parameters through the funded depth with venue fees on both sides. Values of 1.0 or above mean the depth was fully survived before allocated quote ran out.

Decision Record. The four contract values published per asset per oracle pass: active, grid_interval, buy_qty, sell_qty. This is the entire conversation between the engine and a strategy about capital sizing. Generated by exactly one code path and consumed everywhere; raw floats, normalized only at the exchange layer.

Domain (OCaml 5). An isolated parallel execution unit in OCaml 5. Each trading asset in Dio runs in its own domain, so the engine gets true parallelism and one asset's fault does not propagate to another's. Domains are not isolated from one another's memory: they share the engine's caches, feed registries, and capital accounting, and each of those structures carries a declared access discipline. The isolation also guarantees that strategy state for an asset has exactly one writer.

Fear & Greed Index. A market sentiment indicator (0-100) used to resolve the accumulation buffer. For digital assets, Dio uses the CoinMarketCap index; for equities, the CNN index. Low values indicate fear, high values indicate greed.

Grid Interval. The percentage spacing between ladder rungs, configured as hardened [min, max] bounds on the strategy entry and resolved within those bounds by the oracle's parameter search. The strategy never reads the configuration value directly.

Grid Trading. A trading strategy that places buy and sell orders at predetermined price intervals, allowing for profit capture from incremental price movements without directional prediction.

HODL. A long-term investment strategy where assets are retained despite short-term market volatility. Dio's accumulation mechanisms embody the HODL philosophy by systematically growing base asset positions through trading profits.

Jacobs Ladder. The example strategy shipped with the engine and run publicly on diophantsolutions.com. It maintains one trailing buy below the price, sells each filled buy once at the fill price raised by one interval, never cancels placed sells, and runs its sell leg even while inactive because sells need inventory. It is one strategy the engine can run; nothing about it is built into the engine.

Lock-Free Communication. A concurrency pattern that uses atomic compare-and-set operations for zero-contention reads across OCaml 5 domains.

Passive Quoting. Placing orders that rest on the book so the strategy earns the spread. A strategy chooses this by setting the post-only attribute on the orders it constructs; the engine does not impose it. Whether a venue enforces it is an adapter capability: honoured on Kraken, Hyperliquid, and Lighter, discarded on Alpaca and Interactive Brokers, where the behaviour depends on engine-side price clamping.

Mean Reversion. A financial principle stating that asset prices tend to return to their historical average after extreme movements. Ladder trading leverages mean reversion to capture volatility-driven gains.

Parameter Search. The oracle's resolution of spacing and size within hardened bounds. Three branches in order: Unreachable falls back to the conservative corner, Reachable takes the largest size at the tightest spacing meeting the survival target biased by aggressiveness, and Surplus takes maximum size at minimum spacing.

Platform Facts. The declared, validated surface a strategy file reads engine state through, using $platform expressions such as price.nan, oracle.halted, or buy.capital.low. Facts are published by the engine and resolved to concrete values at run time, so a strategy file never calls into the engine directly.

Post-Only Order. A limit order the venue rejects if it would immediately execute against the opposing book. Set per order by the strategy, and honoured by the venue only where the adapter supports it.

Reserved Base. Base asset set aside by the persistence layer from profitable sell fills, excluded from future sell sizing. A cost-averaging mechanism funded from trading gains that survives engine restarts.

Runway. The drawdown budget the ladder must fund, derived from the asset's history: the realized decline from all-time high, the maximum historical peak-to-trough decline, and a floor price below which the funding target extends to the all-time low.

Sharpe Ratio. A measure of risk-adjusted return that evaluates investment performance relative to its volatility. Cited in section 2 as a basis for comparing grid and trend-following backtests.

Strategy File. A declarative script, strategies/<name>.strategy, that defines an asset's trading behaviour: the events it reacts to, the ordered steps each event drives, the state it remembers, and the guards on each step. Configuration binds one file per asset by name, and the engine refuses to start an asset with no file bound. Changing which strategy an asset runs is a configuration change, and the action registry is the designed extension point for capabilities beyond what the shipped vocabulary covers.

Survivability Posture. The risk posture of Jacobs Ladder: traditional order-level controls (stop-losses, hedging, exits) removed and replaced with structural survivability constraints computed by the oracle. The ladder accepts unrestricted downside exposure per order while aggregate risk is constrained by capital sizing, accumulation gating, and spacing resolved from measured history on every pass. An overlay is a separate policy with its own explicit stops; it does not change the ladder's posture.

Volatility. The extent of an asset's price fluctuations over time. Dio treats volatility as a source of systematic returns.