tax-lawyer-evidence-graph

name	tax-lawyer-evidence-graph
description	Evidence graph construction for tax audit trails. Each Satisfies check emits EvidenceNode structs with Blake3 content hashes. Evidence chains are tamper-evident and link legislative citations to factual findings.
version	1.0.0
tags	["evidence","blake3","audit","hash","chain","arc-kit-au","provenance"]
tier	ch0nky
complexity	6
applies_to	["evidence graph","audit trail","Blake3","evidence chain","provenance","tamper-evident"]
output_types	[".json",".rs"]
depends_on	["tax-lawyer-ufo-types"]
unlocks	[]
metadata	{"ufo_stereotype":"Perdurant","legislation":[],"iso_types":[]}

Evidence Graph Pattern

Every tax compliance check MUST produce an evidence graph — a directed acyclic graph (DAG) of EvidenceNode structs linked by EvidenceEdge provenance arcs.

EvidenceNode

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct EvidenceNode {
    pub id: Uuid,                        // stable identifier
    pub evidence_type: EvidenceType,     // Claim | Statistic | Observation
    pub body: String,                    // human-readable finding
    pub citation: String,                // "ITAA 1997 s 355-25(1)(a)"
    pub hash: String,                    // Blake3(body || citation) as hex
    pub timestamp: chrono::DateTime<Utc>,
    pub verdict: Verdict,                // Pass | Fail | Inconclusive
}

pub enum EvidenceType {
    Claim,        // normative assertion derived from legislation
    Statistic,    // quantitative measurement (dollar amounts, dates, counts)
    Observation,  // factual record (existence of documents, entity state)
}

pub enum Verdict {
    Pass,
    Fail,
    Inconclusive,
}

Blake3 Hashing

use blake3::Hasher;

pub fn hash_evidence(body: &str, citation: &str) -> String {
    let mut hasher = Hasher::new();
    hasher.update(body.as_bytes());
    hasher.update(b"||");
    hasher.update(citation.as_bytes());
    hasher.finalize().to_hex().to_string()
}

Blake3 is chosen over SHA-256:

• 3–5× faster on modern hardware
• SIMD-parallel tree hashing
• Same 256-bit security margin

EvidenceEdge (provenance arc)

pub struct EvidenceEdge {
    pub from_id: Uuid,   // prerequisite node
    pub to_id: Uuid,     // dependent node
    pub edge_type: EvidgeEdgeType,
}

pub enum EvidgeEdgeType {
    Supports,     // node A supports the conclusion of node B
    Contradicts,  // node A contradicts node B
    Derives,      // node B is derived from node A (computation)
    Cites,        // node A cites node B as legislative authority
}

Evidence Chain Construction Pattern

pub fn build_au_rd_evidence(activity: &AuRdActivity) -> Vec<EvidenceNode> {
    let mut nodes = vec![];

    // 1. Existence check (Observation)
    let obs = EvidenceNode {
        id: Uuid::new_v4(),
        evidence_type: EvidenceType::Observation,
        body: format!("AuRdActivity '{}' exists with LEI {}", activity.activity_name, activity.lei),
        citation: "ITAA 1997 s 355-25",
        hash: hash_evidence(&body, &citation),
        timestamp: Utc::now(),
        verdict: Verdict::Pass,
    };
    nodes.push(obs);

    // 2. Core activity test (Claim)
    let claim = EvidenceNode {
        evidence_type: EvidenceType::Claim,
        body: format!("Activity domain {:?} is eligible under experimental activities test", activity.domain),
        citation: "ITAA 1997 s 355-25(1)(a) — experimental activities in a field of science/technology",
        // ...
    };
    nodes.push(claim);

    nodes
}

arc-kit-au Integration

arc-kit-au is b00t's internal evidence arc library (future). Until shipped:

• Store evidence nodes in-memory as Vec<EvidenceNode>
• Serialize to JSONL for audit log: ~/.b00t/tax-audit-<date>.jsonl
• Each line = one EvidenceNode JSON

Output JSONL format

{"id":"uuid","evidence_type":"Claim","body":"...","citation":"ITAA 1997 s 355-25","hash":"...","verdict":"Pass"}
{"id":"uuid","evidence_type":"Statistic","body":"Expenditure AUD 250,000 for FY2025","citation":"ITAA 1997 s 355-45","hash":"...","verdict":"Pass"}

Audit Trail Requirements

For ATO R&D offset claims:

• Evidence must exist for each DoD criterion (355-25, 355-30, 355-35, 355-45)
• Expenditure evidence must reference source documents (invoices, timesheets)
• All hashes must be reproducible from the original body+citation strings

For IRS R&D credit (Form 6765):

• Evidence per QRE category (wages, supplies, contract research)
• 4-part test satisfaction must be documented per activity (not just aggregate)

b00t:map v1

summary: Blake3 evidence graph construction for ATO/IRS audit trails

tags: evidence, blake3, audit, hash, provenance, arc-kit-au

tier: ch0nky

complexity: 6