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Trust Function (TF)

A Trust Function is a serverless function that consumes the provenance tree of a resource and translates the accumulated metadata into a quantifiable trust level for the user or system.

Purpose​

Trust Functions provide:

  • Trust Scoring: Numerical or categorical trust ratings
  • Transparency: Explanation of trust calculation
  • Decision Support: Help users assess content reliability
  • Automation: Enable trust-based workflows

Inputs​

Trust Functions analyze:

  • Provenance chains
  • Agent reputation scores
  • Signature verification results
  • Source authority levels
  • Time decay factors
  • Blockchain verification status

Outputs​

Trust Functions produce:

  • Trust Score: Numeric (0-100) or categorical (High/Medium/Low)
  • Confidence Level: Certainty of the score
  • Explanation: Human-readable reasoning
  • Factors: Contributing elements (positive/negative)
  • Recommendations: Suggested actions

Example Trust Calculation​

function calculateTrust(resource) {
  let score = 0;
  
  // Source authority (0-40 points)
  if (resource.source === "EMA") score += 40;
  else if (resource.source === "FDA") score += 40;
  else if (resource.source === "Certified Manufacturer") score += 30;
  
  // Provenance completeness (0-30 points)
  score += resource.provenanceChain.length * 5;
  
  // Signature verification (0-30 points)
  if (resource.signatureValid) score += 30;
  
  return {
    score: Math.min(score, 100),
    level: score > 80 ? "High" : score > 50 ? "Medium" : "Low"
  };
}

Use Cases​

Content Verification​

Assess ePI or Supporting Material trustworthiness before presentation.

Lens Selection​

Choose Lenses based on trust scores of their authors.

Connector Prioritization​

Prefer Connectors to more trusted sources.

Alert Generation​

Warn users when content has low trust scores.

Architecture​

  • Serverless: Function-as-a-Service deployment
  • On-demand: Called when trust assessment needed
  • Stateless: No persistent state between calls
  • Extensible: Custom functions for specific use cases

Development​

Trust Functions can be:

  • Developed by FOSPS community
  • Customized per deployment
  • Validated against test datasets
  • Inspected via CTF Inspector