SPARQL Compliance Matrix

pg_ripple implements the full SPARQL 1.1 specification suite. This page details conformance status for every feature in the W3C SPARQL 1.1 Query, Update, and Protocol recommendations.

SPARQL 1.1 Query — Query Forms

SPARQL 1.1 Query — Algebra Operations

SPARQL 1.1 Query — Property Paths

SPARQL 1.1 Query — Aggregates

SPARQL 1.1 Query — Built-in Functions

SPARQL 1.1 Query — Typed Literals

SPARQL 1.1 Update

SPARQL 1.1 Protocol

SPARQL 1.1 Service Description

SPARQL 1.1 Graph Store HTTP Protocol

RDF-star / SPARQL-star

Extensions Beyond W3C

pg_ripple extends the SPARQL standard with additional capabilities:

Known Limitations

DESCRIBE Strategy Reference (SC13-04, v0.86.0 — supersedes v0.55.0)

pg_ripple supports three DESCRIBE algorithms selectable via the pg_ripple.describe_form GUC (default: cbd), introduced in v0.86.0. The older pg_ripple.describe_strategy GUC is deprecated (see deprecated-gucs.md) and will be removed in v1.0.0.

cbd — Concise Bounded Description (default)

Returns all triples where the described resource appears as subject, plus all triples reachable by following blank-node objects recursively. This is the minimal W3C-defined DESCRIBE semantics.

SET pg_ripple.describe_form = 'cbd';
SELECT * FROM pg_ripple.sparql('DESCRIBE <https://example.org/Alice>');

scbd — Symmetric Concise Bounded Description

Extends CBD by also including all triples where the described resource appears as object. This captures both outgoing and incoming edges. Suitable when you need the full neighbourhood of a resource.

SET pg_ripple.describe_form = 'scbd';
SELECT * FROM pg_ripple.sparql('DESCRIBE <https://example.org/Alice>');

symmetric — Permanent Alias for scbd (CB-10, v0.92.0)

symmetric is a permanent alias for scbd for readability:

SET pg_ripple.describe_form = 'symmetric';
SELECT * FROM pg_ripple.sparql('DESCRIBE <https://example.org/Alice>');

Alias contract: The alias symmetric = scbd is guaranteed stable for the pg_ripple 1.x API line. It will not be removed without a deprecation cycle and will only diverge from scbd semantics if the W3C SCBD and "symmetric extension" definitions separate in a future RDF standard. This guarantee was formally documented in v0.92.0.

Choosing a Form

The GUC can be set at the session or transaction level:

-- Session-level
SET pg_ripple.describe_form = 'scbd';

-- Transaction-level
BEGIN;
SET LOCAL pg_ripple.describe_form = 'cbd';
SELECT * FROM pg_ripple.sparql('DESCRIBE <https://example.org/Bob>');
COMMIT;

Migration note: Replace SET pg_ripple.describe_strategy = 'simple' with SET pg_ripple.describe_form = 'cbd' (the simple strategy is now the CBD default). The strategy scbd maps directly to describe_form = 'scbd'.

Blank-Node Limitations in RDF-star Quoted Triples (C13-03, v0.85.0)

Blank nodes inside RDF-star quoted triples (e.g., << _:b1 :p :o >>) do not have a canonical round-trip form in pg_ripple. When an anonymous blank node appears as the subject or object of a quoted triple, encoding and then decoding the same triple may produce a different blank-node label.

Workaround: Use named IRIs or well-known blank-node identifiers (e.g., _:b1 with a stable label) as subjects/objects of quoted triples. Alternatively, avoid blank nodes entirely in the subject/object positions of << >> patterns.

Impact: This limitation only affects blank-node-in-quoted-triple patterns. Regular blank nodes in non-quoted triples round-trip correctly.

GRAPH ?g Default-Graph Exclusion (C13-06, v0.85.0)

Per SPARQL 1.1 specification §8.3, when GRAPH ?g { ... } is used, the variable ?g is bound only to **named variable ?g is bound only to **named variable ?g is bound only to **named variable This is conformavariable ?gis bound only to **named variable?gis bound only to wivariable?gis bound only to **named variable?gis bound only to **na ?pvariable?gis bound only to **named variable?gis bound only to **naatvariable?gis bound only to **named variable?g` is bound only to **named ns triples.

To query the default graph specifically, use: WHERE nd```````````````````````````````````````````````````````````````````````valu````````````````````````````````````````````````````````````````````````````cis``````````````````````````````````````````````````````````````truncate```````````````````````````````````````````````````seconds) when serializing xsd:dateTime literals back to N-Triples format.

Example:

# Input:  "2024-01-01T12:00:00.123456789Z"^^xsd:dateTime
# Stored: 2024-01-01 12:00:00.123457+00  (rounded to microseconds by PG)
# Output: "2024-01-01T12:00:00.123"^^xsd:dateTime  (truncated to 3 decimal places)

Sub-millisecond precision is silently dropped in the output. If you require sub-millisecond precision, store the value as a plain string literal and perform comparisons manually.

RDF 1.2 / SPARQL-star Compliance Matrix (STD-02, v0.91.0)

pg_ripple supports RDF-star via the oxrdf 0.3 data model and the qt_s/qt_p/qt_o dictionary columns introduced in v0.4.0. The table below maps each RDF 1.2 / SPARQL-star feature to its implementation status.

Overall: pg_ripple's RDF-star foundation (v0.4.0) covers the most widely-used SPARQL-star patterns. Remaining gaps depend on spargebra 0.x adopting the SPARQL 1.2 grammar and are tracked as post-v1.0.0 work (see SPARQL 1.2 tracking).

<< >> Position Support Matrix (L15-08, v0.97.0)

This table summarises which positions a quoted triple pattern << s p o >> can appear in across all SPARQL 1.1 query and update forms. Use this matrix when writing queries that combine RDF-star with other features.