Architecture

FactHarbor uses a modular-monolith architecture (POC → Beta 0) designed to evolve into a distributed, federated, multi-node system (Release 1.0+).
Modules are strongly separated, versioned, and auditable. All logic is transparent and deterministic.

High-Level System Architecture

FactHarbor is composed of the following major modules:

• UI Frontend
• REST API Layer
• Core Logic Layer
  – Claim Processing  
  – Scenario Engine  
  – Evidence Repository  
  – Verdict Engine  
  – Re-evaluation Engine  
  – Roles / Identity / Reputation
• AKEL (AI Knowledge Extraction Layer)
• Federation Layer
• Workers & Background Jobs
• Storage Layer (Postgres + VectorDB + ObjectStore)

Key ideas:

• Core logic is deterministic, auditable, and versioned 
• AKEL drafts structured outputs but never publishes directly 
• Workers run long or asynchronous tasks 
• Storage is separated for scalability and clarity 
• Federation Layer provides optional distributed operation 

Storage Architecture

FactHarbor separates structured data, embeddings, and evidence files:

• PostgreSQL — canonical structured entities, all versioning, lineage, signatures 
• Vector DB (Qdrant or pgvector) — semantic search, duplication detection, cluster mapping 
• Object Storage — PDFs, datasets, raw evidence, transcripts 
• Optional (Release 1.0): Redis for caching, IPFS for decentralized object storage 

Core Backend Module Architecture

Each module has a clear responsibility and versioned boundaries to allow future extraction into microservices.

Claim Processing Module

Responsibilities:

• Ingest text, URLs, documents, transcripts, federated input 
• Extract claims (AKEL-assisted) 
• Normalize structure 
• Classify (type, domain, evaluability, safety) 
• Deduplicate via embeddings 
• Assign to claim clusters 

Flow:  
Ingest → Normalize → Classify → Deduplicate → Cluster

Scenario Engine

Responsibilities:

• Create and validate scenarios 
• Enforce required fields (definitions, assumptions, boundaries...) 
• Perform safety checks (AKEL-assisted) 
• Manage versioning and lifecycle 
• Provide contextual evaluation settings to the Verdict Engine 

Flow:  
Create → Validate → Version → Lifecycle → Safety

Evidence Repository

Responsibilities:

• Store metadata + files (object store) 
• Classify evidence 
• Compute preliminary reliability 
• Maintain version history 
• Detect retractions or disputes 
• Provide structured metadata to the Verdict Engine 

Flow:  
Store → Classify → Score → Version → Update/Retract

Verdict Engine

Responsibilities:

• Aggregate scenario-linked evidence 
• Compute likelihood ranges 
• Generate reasoning chain 
• Track uncertainty factors 
• Maintain verdict version timelines 

Flow:  
Aggregate → Compute → Explain → Version → Timeline

Re-evaluation Engine

Responsibilities:

• Listen for upstream changes 
• Trigger partial or full recomputation 
• Update verdicts + summary views 
• Maintain consistency across federated nodes 

Triggers include:

• Evidence updated or retracted 
• Scenario definition or assumption changes 
• Claim type or evaluability changes 
• Contradiction detection 
• Federation sync updates 

Flow:  
Trigger → Impact Analysis → Recompute → Publish Update

AKEL Integration Summary

AKEL is fully documented in its own chapter.
Here is only the architectural integration summary:

• Receives raw input for claims 
• Proposes scenario drafts 
• Extracts and summarizes evidence 
• Gives reliability hints 
• Suggests draft verdicts 
• Monitors contradictions 
• Syncs metadata with trusted nodes 

AKEL runs in parallel to human review — never overrides it.

Federated Architecture

Each FactHarbor node:

• Has its own dataset (claims, scenarios, evidence, verdicts) 
• Runs its own AKEL 
• Maintains local governance and reviewer rules 
• May partially mirror global or domain-specific data 
• Contributes to global knowledge clusters 

Nodes synchronize via:

• Signed version bundles 
• Merkle-tree lineage structures 
• Optionally IPFS for evidence 
• Trust-weighted acceptance 

Benefits:

• Community independence 
• Scalability 
• Resilience 
• Domain specialization 

Request → Verdict Flow

Simple end-to-end flow:

User → UI Frontend → REST API → FactHarbor Core
      → (Claim Processing → Scenario Engine → Evidence Repository → Verdict Engine)
      → Summary View → UI Frontend → User

Federation Sync Workflow

Sequence:

Detect Local Change → Build Signed Bundle → Push to Peers → Validate Signature → Merge or Fork → Trigger Re-evaluation

Versioning Architecture

All entities (Claim, Scenario, Evidence, Verdict) use immutable version chains:

• VersionID 
• ParentVersionID 
• Timestamp 
• AuthorType (Human, AI, ExternalNode) 
• ChangeReason 
• Signature (optional POC, required in 1.0)