vcl-vs-sql.adoc

VCL vs SQL: A Comparative Guide

Table of Contents

• 1. Introduction
• 2. Concept Comparison
• 3. What VCL Lacks That SQL Has
• 4. What VCL Has That SQL Lacks
• 5. Example Comparisons
  • 5.1. Retrieving an Entity
  • 5.2. Finding Related Entities
  • 5.3. Full-Text Search
  • 5.4. Similarity Search
  • 5.5. Verified Query (No SQL Equivalent)
• 6. Summary

1. Introduction

VCL (VeriSim Consonance Language) is the query language for VeriSimDB, a 6-core multimodal database. While VCL borrows familiar keywords from SQL (SELECT, FROM, WHERE, LIMIT, OFFSET), it serves a fundamentally different purpose.

VCL is read-only. It does not support INSERT, UPDATE, or DELETE statements. All mutations go through the Octad API (Rust core or Elixir orchestration layer). This is a deliberate design choice: VeriSimDB treats writes as coordinated multi-modal operations that must maintain consistency across all eight modality stores (Graph, Vector, Tensor, Semantic, Document, Temporal, Provenance, Spatial). A simple INSERT statement cannot express the cross-modal invariants that a Octad write requires.

VCL is multimodal. Where SQL selects columns from relational tables, VCL selects modalities from octad stores or federations. A single VCL query can retrieve graph edges, vector embeddings, tensor slices, semantic annotations, document text, and temporal versions in one pass.

VCL is federation-aware. Queries can target a local STORE, a specific HEXAD entity, or a FEDERATION of distributed VeriSimDB instances, with configurable drift policies governing cross-instance consistency.

2. Concept Comparison

Concept	VCL	SQL
Column/Field Selection	SELECT with modalities: GRAPH, VECTOR, TENSOR, SEMANTIC, DOCUMENT, TEMPORAL, PROVENANCE, SPATIAL, or * (all eight). Modalities can be combined: SELECT GRAPH, VECTOR, SEMANTIC.	SELECT with column names or * for all columns.
Data Source	FROM STORE <name>, FROM HEXAD <uuid>, or FROM FEDERATION <name>. A STORE is a collection of octad entities. A HEXAD is a single entity addressed by UUID. A FEDERATION spans multiple VeriSimDB instances.	FROM <table> or FROM <table> AS <alias>. Tables are flat relational structures.
Filtering	WHERE supports field conditions (h.field = value) and full-text predicates: CONTAINS(h.content, "term") for substring matching, MATCHES(h.content, "pattern") for pattern matching. Graph traversal uses Cypher-inspired syntax: (h)-[:EDGE_TYPE]→(target). Vector similarity uses SIMILAR TO […​].	WHERE supports standard comparison operators, LIKE, IN, BETWEEN, IS NULL, boolean combinators (AND, OR, NOT), and subqueries.
Joins	No JOINs. Graph modality replaces relational joins entirely. Relationships are first-class: (h)-[:CITES]→(target) traverses edges without explicit join syntax. Cross-modal correlation is implicit within a octad.	JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN, CROSS JOIN with ON conditions.
Mutations	None. VCL is strictly read-only. All writes go through the Octad API: POST /api/octads (create), PUT /api/octads/:id (update), DELETE /api/octads/:id (delete). This ensures cross-modal consistency.	INSERT INTO, UPDATE …​ SET, DELETE FROM, MERGE, TRUNCATE.
Verification	PROOF <type>(<contract>) clause requests a verifiable guarantee about the result. Six proof types: EXISTENCE, INTEGRITY, CONSISTENCY, PROVENANCE, FRESHNESS, AUTHORIZATION. No SQL equivalent exists.	No equivalent. SQL has no mechanism for cryptographic or type-theoretic verification of query results.
Pagination	LIMIT n and OFFSET n work identically to SQL.	LIMIT n and OFFSET n (or vendor-specific: TOP, FETCH FIRST).

3. What VCL Lacks That SQL Has

VCL is intentionally minimal. The following SQL features have no VCL equivalent:

SQL Feature	VCL Status
GROUP BY	Not supported. Aggregation is performed application-side or through the Elixir orchestration layer.
ORDER BY	Not supported. Result ordering is determined by the modality store (e.g., vector similarity ranking, graph traversal order, temporal chronological order).
Aggregate functions (COUNT, SUM, AVG, MIN, MAX)	Not supported. VCL returns raw data; aggregation is a consumer responsibility.
Subqueries	Not supported. Queries are flat. Compose results in application code or use the Elixir query router for multi-step workflows.
DISTINCT	Not supported. Octad entities are inherently unique (UUID-addressed), so deduplication is rarely needed.
HAVING	Not supported (requires GROUP BY).
UNION / INTERSECT / EXCEPT	Not supported. Use multiple queries and combine results application-side.
CREATE TABLE / DDL	Not supported. Schema is managed through the ReScript registry and Elixir SchemaRegistry.
Window functions (ROW_NUMBER, RANK, OVER)	Not supported.
Stored procedures / triggers	Not supported. Business logic lives in the Elixir orchestration layer.

4. What VCL Has That SQL Lacks

VCL Feature	Description
PROOF clause	Requests a verifiable proof certificate alongside query results. Six proof types cover existence, integrity, consistency, provenance, freshness, and authorization guarantees. Enables dependent-type verification via the VCL-DT path.
Multimodal SELECT	Select specific modalities (GRAPH, VECTOR, TENSOR, SEMANTIC, DOCUMENT, TEMPORAL) or all (*). No SQL equivalent for querying fundamentally different data representations of the same entity.
FEDERATION queries	Target distributed VeriSimDB instances: FROM FEDERATION <name>. Includes drift policies that govern how cross-instance consistency is enforced during query execution.
Drift policies	DRIFT POLICY <name> attaches consistency enforcement rules to federated queries. Drift detection and repair are first-class query concerns.
Octad entity addressing	FROM HEXAD <uuid> addresses a single cross-modal entity by its UUID. All six modalities are accessible through one query against one identifier.
Graph traversal syntax	Cypher-inspired patterns directly in WHERE: (h)-[:RELATES_TO]→(target). No need for separate graph query language or JOIN emulation.
Vector similarity	WHERE h.embedding SIMILAR TO [0.1, 0.2, …​] performs nearest-neighbor search natively. SQL requires extensions (pgvector) or external systems.
Full-text predicates	CONTAINS(h.content, "term") and MATCHES(h.content, "pattern") are built-in, backed by the Tantivy-powered document store.

5. Example Comparisons

5.1. Retrieving an Entity

SQL:

SELECT *
FROM entities
WHERE id = '550e8400-e29b-41d4-a716-446655440000';

VCL (Slipstream):

SELECT *
FROM HEXAD 550e8400-e29b-41d4-a716-446655440000

The VCL version returns all eight modalities for that octad. The SQL version returns only the columns in the entities table.

5.2. Finding Related Entities

SQL (requires JOIN):

SELECT e2.*
FROM entities e1
JOIN relationships r ON e1.id = r.source_id
JOIN entities e2 ON r.target_id = e2.id
WHERE e1.id = '550e8400-e29b-41d4-a716-446655440000'
  AND r.type = 'CITES';

VCL (graph traversal):

SELECT GRAPH
FROM HEXAD 550e8400-e29b-41d4-a716-446655440000
WHERE (h)-[:CITES]->(target)

VCL eliminates the triple-table JOIN pattern entirely. Graph relationships are native.

5.3. Full-Text Search

SQL (PostgreSQL example):

SELECT *
FROM documents
WHERE to_tsvector('english', content) @@ to_tsquery('quantum & computing');

VCL:

SELECT DOCUMENT
FROM STORE research_papers
WHERE CONTAINS(h.content, "quantum computing")
LIMIT 20

5.4. Similarity Search

SQL (requires pgvector extension):

SELECT *, embedding <-> '[0.1, 0.2, 0.3, 0.4]' AS distance
FROM entities
ORDER BY embedding <-> '[0.1, 0.2, 0.3, 0.4]'
LIMIT 10;

VCL:

SELECT VECTOR
FROM STORE research_papers
WHERE h.embedding SIMILAR TO [0.1, 0.2, 0.3, 0.4]
LIMIT 10

5.5. Verified Query (No SQL Equivalent)

VCL-DT (dependent type path):

SELECT *
FROM HEXAD 550e8400-e29b-41d4-a716-446655440000
PROOF INTEGRITY(DataIntegrityContract)

This returns the octad data plus a cryptographic proof certificate asserting data integrity. SQL has no mechanism for this.

6. Summary

Capability	SQL	VCL
Relational queries	Yes	No
Multimodal queries	No	Yes
Mutations (INSERT/UPDATE/DELETE)	Yes	No (API only)
JOINs	Yes	No (graph modality)
Aggregation (GROUP BY, COUNT, SUM)	Yes	No
Subqueries	Yes	No
PROOF verification	No	Yes
Federation with drift policies	No	Yes
Graph traversal	No (or extensions)	Yes (native)
Vector similarity	No (or extensions)	Yes (native)
Full-text search	Extensions	Yes (native)
Ordering (ORDER BY)	Yes	No
Pagination (LIMIT/OFFSET)	Yes	Yes

VCL is not a replacement for SQL. It is a purpose-built query language for a multimodal database that treats entities as six simultaneous representations rather than rows in flat tables. Use SQL when you need relational algebra. Use VCL when you need to query across modalities with optional formal verification.