pacr-types

The PACR 6-tuple — physically annotated causal records for AI agents.

Part of the Aevum physics kernel.

What It Is

pacr-types defines the PACR 6-tuple — the immutable schema that every Aevum record must satisfy:

R = (ι, Π, Λ, Ω, Γ, P)

Symbol	Name	Type	Physical Origin
ι	Causal Identity	`CausalId` (128-bit ULID)	Logical identity
Π	Predecessor Set	`SmallVec<[CausalId; 4]>`	Special relativity causal order
Λ	Landauer Cost	`Estimate<f64>` (joules)	Landauer's principle
Ω	Resource Triple	`ResourceTriple` (E, T, S)	Conservation + Margolus-Levitin
Γ	Cognitive Split	`CognitiveSplit` (S_T, H_T)	CSSR ε-machine
P	Opaque Payload	`bytes::Bytes`	Completeness axiom

Key Properties

Zero dependencies on non-std crates except serde, smallvec, bytes, thiserror
#![forbid(unsafe_code)] — trust root; zero tolerance
Estimate<T> wraps every physical measurement with { point, lower, upper } — uncertainty at the protocol level
Ω.energy ≥ Λ always enforced — actual cost cannot be less than Landauer floor
No self-reference in Π — a record cannot be its own causal predecessor

Usage

use pacr_types::{PacrRecord, PacrBuilder, Estimate, ResourceTriple, CognitiveSplit};
use bytes::Bytes;

let record = PacrBuilder::new()
    .landauer(Estimate::exact(2.854e-21))
    .resources(ResourceTriple {
        energy: Estimate::exact(1e-18),
        time:   Estimate::exact(1e-9),
        space:  Estimate::exact(512.0),
    })
    .cognitive(CognitiveSplit {
        statistical_complexity: Estimate::exact(3.2),
        entropy_rate:           Estimate::exact(0.8),
    })
    .payload(Bytes::from("hello causal world"))
    .build()?;

assert!(record.validate().is_ok());

Invariants

Estimate<T>: lower ≤ point ≤ upper always. Estimate::new() is fallible; Estimate::exact() sets all three to the same value.
Ω.energy ≥ Λ — actual energy cost ≥ Landauer floor (validated by PacrRecord::validate()).
Schema is append-only — existing fields never change semantics.

License