12. Appendix: Schema Reference

12.1 Schema Versions

Artifact	Schema Version	File
Graph	graph.v1	.ctn/<id>/graph.json
BSG	bsg.v1	.ctn/<id>/bsg.json
Snapshot	snapshot.v1	.ctn/snapshots/<id>.json
Index Metadata	index-metadata.v1	.ctn/index.json
File Cache	file-cache.v1	.ctn/local/cache/ast_cache.db
BSG Plugin	bsg-plugin.v1	batho/bsg/schemas/bsg-plugin-schema-v1.json

Schema Dependency Graph

Figure 27: Schema Dependency Graph - Dependency diagram showing the relationships between configuration schemas, runtime artifacts, and cache layers.

12.2 Directory Structure

.ctn/
├── index.json                    # Index metadata + history
├── local/
│   ├── cache/
│   │   └── ast_cache.db          # SQLite AST entity cache
│   ├── metrics/
│   │   └── metrics.json          # Indexing performance metrics
│   └── sync/
│       └── artifact_registry.db  # SQLite artifact registry
├── snapshots/
│   └── batho_<uuid>_<ts>.json   # Time Machine snapshots
└── <index_id>/
    ├── graph.json                # Entities + relationships
    ├── bsg.json                  # Structured symbol graph
    └── files.md                  # All files by category

12.3 Glossary

Term	Definition
AST	Abstract Syntax Tree — structured representation of source code
BSG	Batho Structured Graph — compressed, queryable code representation
CTN	Content directory — Batho's output workspace
Entity	A node in the code graph (function, class, etc.)
Hypergraph	Graph where edges can connect any number of nodes
Patch	Incremental update to a snapshot
Relationship	A directed edge between entities
Snapshot	Immutable point-in-time capture of the code graph
Symbol Index	Cross-file lookup table for imports and exports

12.4 Error Codes

Code	Description
E001	File not found
E002	Parse error
E003	Cache corruption
E004	Snapshot mismatch
E005	Permission denied
E100	Configuration error
E200	Plugin load failure
E300	Storage error