public-source-gating

Hard rules (public sources only)

1. Every authority/proposition outcome MUST be one of:

   • VERIFIED_CORRECT (public source retrieved and supports)
   • VERIFIED_ERROR (public source retrieved and contradicts OR shows mismatch)
   • UNVERIFIABLE_PUBLIC (not found / ambiguous / blocked / missing coverage)

2. NEVER state "does not exist" unless you have retrieved material proving mismatch. If you cannot retrieve the authority text from public sources, label UNVERIFIABLE_PUBLIC.

3. Every conclusion MUST include:

   • retrieval URL(s) attempted,
   • timestamp,
   • cached artefact path + SHA256,
   • short reason for any failure.

Source Acquisition Policy (v0.2)

Permitted Sources (Priority Order)

1. Find Case Law (National Archives) - Primary for UK case law

   • Preferred for all UK neutral citations
   • Deterministic URL construction before searching
   • Atom feed search in restricted mode (max 10 results per query)
   • Document retrieval via /{document_uri}/data.xml

2. BAILII - Secondary fallback for UK case law

   • Used only when FCL fails or not applicable
   • Case-scoped, targeted retrieval only
   • Per-job cap: 25-50 fetches maximum (configurable)

3. User-provided documents and links - Always permitted

Prohibited Activities

NEVER:

• Crawl, mirror, or bulk-download from BAILII or Find Case Law
• Build a general corpus from any public source
• Walk indices, pagination, or "related cases" links
• Perform systematic computational analysis without licensing

Find Case Law Specific Rules

1. Open Justice Licence Compliance:

   • Default mode: URL fetch + API retrieval for specific documents only
   • No computational analysis without explicit permission
   • If bulk searching required: mark as FCL_SEARCH_MODE=RESTRICTED

2. Rate Limiting (mandatory):

   • Global limit: 1,000 requests per 5 minutes per IP (API spec)
   • Polite limit: 1 request per second (system default)
   • Handle 429 responses: backoff + retry (3 attempts max)
   • After retries exhausted: mark remaining UNVERIFIABLE_PUBLIC

3. Resolution Algorithm (conservative):

   Step 1: Deterministic URL Construction
     Try: GET /{court}/{year}/{num}/data.xml
     If 200: RESOLVED
     If 404: Proceed to Step 2
   
   Step 2: Atom Feed Search (Restricted)
     Build 2-3 targeted queries (court filter, neutral citation, party)
     Fetch: per_page=10, page=1 only (max 2 pages)
     Score: exact identifier match > party+year+court match
     If exactly one high-confidence: RESOLVED
     If multiple: UNVERIFIABLE_PUBLIC (ambiguous)
     If none: Proceed to Step 3
   
   Step 3: BAILII Fallback (Optional)
     Only if within per-job BAILII limit
     Try pattern match
     Respect rate limit
   

4. Caching Requirements:

   • Store raw XML/HTML artefact
   • Compute SHA256 hash locally
   • Store FCL contenthash from Atom (if available)
   • Store updated timestamp from Atom
   • Create metadata JSON with all retrieval details

BAILII Specific Rules

1. Hard Limits (enforced per job):

   • Per-job cap: 25-50 fetches (configurable)
   • Rate limit: 1 request per second minimum
   • Strict caching: no refetching within job if cached

2. Pattern Matching Only:

   • Support 9 UK court types with deterministic URL templates
   • No web search or creative guessing
   • If pattern doesn't match: mark unresolvable

Evidence Requirements

Every VERIFIED_* conclusion MUST include:

1. Source URL(s) - All URLs attempted and which succeeded
2. Retrieval timestamp - ISO 8601 format
3. Cached artefact - Path relative to project root
4. Content hash - SHA256 of cached content
5. Metadata - HTTP status, content type, content length
6. Quoted snippets - From retrieved artefact only (no fabrication)

Every UNVERIFIABLE_PUBLIC MUST include:

1. URLs attempted - All resolution attempts
2. HTTP status codes - Or resolution failure reasons
3. Reason - No pattern match / 404 / ambiguous / rate limited
4. Timestamp - When attempts were made

Rate Limit Handling

When rate limits encountered (429 responses):

1. Immediate action:

   • Backoff with exponential delay (1s, 2s, 4s)
   • Retry up to 3 times total
   • Log each retry attempt

2. After exhaustion:

   • Stop making requests to that source for this job
   • Mark remaining citations as UNVERIFIABLE_PUBLIC
   • Include clear note in report:

     "Rate limit reached for [source]. Remaining N citations could not be verified.
     Consider running audit again after delay or increasing per-job limits."
     

3. Never:

   • Continue hammering the API
   • Skip rate limiting to "get results faster"
   • Hide rate limit failures from user