# Enforcing schema contracts for GeoJSON and Shapefiles

In a federated geospatial data mesh, unvalidated vector payloads constitute the primary failure vector for cross-domain routing and tile generation pipelines. When domain teams publish GeoJSON or Shapefile derivatives without strict structural guarantees, the Federated Ownership & Routing Architecture experiences cascading serialization errors that breach downstream SLAs. This guide isolates the exact configuration pattern required to enforce schema contracts at the ingestion boundary, ensuring deterministic behavior across the Schema Contracts for Vector/Tile Data layer.

# Ingestion Boundary & Validation Topology

The enforcement mechanism operates as a synchronous validation gate prior to spatial indexing, topology repair, or tile slicing. Deployment follows a dual-validation pipeline: JSON Schema for GeoJSON geometry/property type enforcement, and GDAL/OGR schema introspection for Shapefile .dbf/.shp alignment. Execution must be strictly idempotent; repeated invocations against identical payloads yield identical validation states without side effects, cache mutation, or partial writes to the staging bucket.

Validation failures must halt pipeline progression before Async Execution for Heavy Spatial Queries is triggered, preventing resource exhaustion on compute clusters. Cross-Domain Routing Strategies rely on validated feature counts and coordinate reference system (CRS) alignment; unverified payloads introduce routing table corruption that propagates to downstream tile caches.

# Exact Configuration Syntax

Deploy the following configuration to the validation sidecar or CI/CD runner. The schema enforces strict type mapping, CRS normalization, and geometry topology constraints.

# contract-validator-config.yaml
validation:
  geojson:
    schema_path: /etc/contracts/geojson/v1/feature-collection.schema.json
    strict_crs: true
    allowed_crs: ["urn:ogc:def:crs:OGC:1.3:CRS84"]
    max_features: 50000
    reject_null_geometry: true
    enforce_flat_properties: true
  shapefile:
    dbf_encoding: "UTF-8"
    enforce_field_mapping: true
    field_map_path: /etc/contracts/shapefile/v1/field-mapping.yaml
    geometry_type: "POLYGON"
    max_record_length: 254
    require_spatial_index: true

Note: RFC 7946 GeoJSON mandates WGS 84 (longitude/latitude) and removes support for the crs member from GeoJSON objects. The canonical CRS URI for RFC 7946-compliant GeoJSON is urn:ogc:def:crs:OGC:1.3:CRS84 (equivalent to EPSG:4326 with axis order longitude, latitude). Do not use urn:ogc:def:crs:EPSG::4326 in GeoJSON contracts, as the axis order differs.

Contract Drift Mitigation: The field_map_path must be version-controlled alongside domain manifests. Any deviation between the .dbf header and the mapping file triggers a hard failure. Legacy GIS exports frequently coerce numeric fields to strings or truncate column names to 10 characters; the validator explicitly rejects these mutations.

# Idempotent Execution & CLI Invocation

Validation commands must return deterministic exit codes (0 for pass, 1 for contract violation, 2 for parser/runtime failure). Use the following invocation patterns for batch processing and CI/CD integration.

# 1. GeoJSON strict contract validation using the jsonschema CLI
python3 -m jsonschema \
  --instance payload.geojson \
  /etc/contracts/geojson/v1/feature-collection.schema.json

# 2. Shapefile schema alignment & geometry type verification
ogrinfo -so -al input.shp | grep -E "Geometry|Layer name|Feature Count"

# 3. CRS verification (must match urn:ogc:def:crs:OGC:1.3:CRS84 for GeoJSON)
ogrinfo -al -so input.shp | grep "SRS WKT"

For batch processing in CI pipelines, wrap the above commands in a script that emits structured JSON exit information:

#!/usr/bin/env bash
set -euo pipefail

INPUT="${1:?Missing input file}"
CONFIG="${2:?Missing config path}"
CORRELATION_ID=$(uuidgen)

echo "Starting validation: correlation_id=${CORRELATION_ID}"

# Geometry type and feature count check
ogrinfo -so -al "${INPUT}" | grep -E "Geometry|Feature Count" || {
  echo '{"level":"ERROR","error_code":"ERR_OGR_PARSE","correlation_id":"'"${CORRELATION_ID}"'"}'
  exit 2
}

echo '{"level":"INFO","status":"pass","correlation_id":"'"${CORRELATION_ID}"'"}'
exit 0

Idempotency Guarantees: The validator reads input streams without modification, writes no temporary artifacts, and relies solely on in-memory schema evaluation. Retry loops with exponential backoff are safe to implement at the orchestrator level; payload state remains unchanged across attempts.

# Diagnostic Log Patterns & Root-Cause Isolation

When validation fails, the pipeline must emit deterministic error codes rather than generic serialization dumps. Structured logs follow the OpenTelemetry semantic conventions for trace correlation.

Standardized Log Schema:

{
  "timestamp": "2024-05-14T08:12:33.001Z",
  "level": "ERROR",
  "correlation_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "validation_stage": "schema_contract",
  "error_code": "ERR_DBF_FIELD_COERCION",
  "payload_hash": "sha256:8f434346648f6b96df89dda901c5176b10a6d83961dd3c1ac88b59b2dc327aa4",
  "details": {
    "field": "POPULATION",
    "expected_type": "integer",
    "actual_type": "string",
    "row_offset": 142
  }
}

Debugging Workflow:

1. Isolate the failing batch using verbose OGR output: ogrinfo -al input.shp | head -50.
2. Parse structured logs: jq -r '.details.field' validation.log | sort | uniq -c to surface column drift.
3. Cross-reference error stacks against field_map_path to identify implicit type coercion in Shapefile .dbf files.
4. For GeoJSON, run:

   jq '.features[] | select(.geometry == null or .geometry.type != "Polygon" or (.geometry.coordinates | length) < 1)' payload.geojson
   

   to surface null geometries or degenerate rings.
5. Verify CRS alignment: ogrinfo -al -so input.shp | grep "SRS WKT" — for Shapefiles destined for GeoJSON output, the SRS must be WGS 84.

Common Failure Signatures:

• ERR_GEOJSON_NESTED_OBJECT: Violates enforce_flat_properties: true. Flatten properties using jq '.features[].properties |= with_entries(select(.value | type != "object"))'.
• ERR_SHP_TRUNCATED_FIELD: DBF column name exceeds 10 characters. Rename at source or update field_map_path with alias mapping.
• ERR_TOPOLOGY_DEGENERATE: Polygon ring contains < 4 coordinate pairs or self-intersects. Reject or route to topology repair queue.

# Pipeline Integration & State Guarantees

The validation gate integrates into Domain Sync Protocols for Spatial Data as a blocking prerequisite. Successful validation emits a signed manifest (checksum.sha256, schema_version.json) that downstream consumers verify before mounting volumes or streaming to API Gateway Mapping for GIS Services.

Deployment Patterns:

• CI/CD Pre-Commit Hook: Blocks merge requests containing invalid vector payloads. Fails fast with pull request annotations.
• Ingress Sidecar: Intercepts object storage uploads (S3/GCS) before triggering tile slicing. Returns HTTP 422 Unprocessable Entity on contract violation.
• Async Batch Validator: Runs on scheduled cron for legacy data lakes. Outputs drift reports when coordinate precision degrades below 1e-6 decimal degrees.

Validation overhead should remain under 150ms per 10k features. Profile with py-spy or perf and adjust max_features thresholds to align with compute node memory limits.

# Escalation Paths & Incident Response Runbook

Validation failures are classified by impact scope and routed through tiered escalation paths.

Runbook Execution Steps:

1. Acknowledge alert via incident management platform. Attach correlation_id and payload_hash.
2. Verify validation gate logs: grep "ERR_" /var/log/contract-validator/*.json | jq -c '{error_code, details}'.
3. If P1, execute kubectl rollout pause deployment/tile-slicer to prevent corrupted geometry propagation.
4. Restore last known-good schema manifest from version control. Re-run validation with lenient mode only if authorized by architecture review.
5. Post-incident: Update field_map_path or GeoJSON schema, publish contract version bump, and notify downstream consumers via API changelog.

External References for Standard Compliance:

• RFC 7946: The GeoJSON Format
• GDAL/OGR Shapefile Driver Specification
• Python jsonschema Validation Library