Add 30+ SPARQL 1.1 built-in functions and the MINUS algebra operator to the
custom SPARQL query backend.
String functions:
- SUBSTR (2-arg and 3-arg forms), STRBEFORE, STRAFTER
- REPLACE (regex with flags), ENCODE_FOR_URI
Numeric functions:
- FLOOR, CEIL, ROUND, ABS
Date/time accessors:
- YEAR, MONTH, DAY, HOURS, MINUTES, SECONDS
- NOW, TZ
Hash functions:
- MD5, SHA1, SHA256, SHA512
Term constructors:
- IRI/URI, BNODE, UUID, STRUUID
Other functions:
- LANGMATCHES, RAND
- EXISTS / NOT EXISTS (with async pre-evaluation to bridge the
sync expression evaluator and async algebra evaluator)
Algebra:
- MINUS set-difference operator
- HAVING already works via rdflib's Filter mapping (verified)
Fix SPARQL ORDER handling
Includes 653 lines of new unit tests covering all added functionality
across expressions, solutions, and algebra layers.
SPARQL 1.1 query service wrapping pub/sub triples interface
Add a backend-agnostic SPARQL query service that parses SPARQL
queries using rdflib, decomposes them into triple pattern lookups
via the existing TriplesClient pub/sub interface, and performs
in-memory joins, filters, and projections.
Includes:
- SPARQL parser, algebra evaluator, expression evaluator, solution
sequence operations (BGP, JOIN, OPTIONAL, UNION, FILTER, BIND,
VALUES, GROUP BY, ORDER BY, LIMIT/OFFSET, DISTINCT, aggregates)
- FlowProcessor service with TriplesClientSpec
- Gateway dispatcher, request/response translators, API spec
- Python SDK method (FlowInstance.sparql_query)
- CLI command (tg-invoke-sparql-query)
- Tech spec (docs/tech-specs/sparql-query.md)
New unit tests for SPARQL query
