FILTER — boolean composition over solutions

Name: pgRDF
Author: Peter Styk

Equality, ordering, boolean composition, term-type tests, bound, in, regex, numeric comparison, string functions.

What it does

A FILTER expression evaluates a boolean over each candidate solution; only the truthy solutions survive. pgRDF supports the full SPARQL 1.1 expression surface that the underlying spargebra algebra and the executor can translate to SQL:

Class	Operators / functions
Comparison	`=`, `!=`, `<`, `<=`, `>`, `>=`
Boolean	`&&`, `\|\|`, `!`
Term-type tests	`isIRI`, `isLiteral`, `isBlank`, `isNumeric`
Binding tests	`bound(?v)`
Set tests	`?v IN (a, b, c)`, `?v NOT IN (...)`
Regex	`REGEX(?v, "pat", "flags")`
Numeric	type-aware on `xsd:integer`, `xsd:decimal`, `xsd:double`
String	`STRLEN`, `UCASE`, `LCASE`, `STR`, `LANG`

Why you'd use it

Data scientists — apply text-search and numeric predicates inside the SPARQL pattern, not in a post-process.
Ontologists — carve subgraphs declaratively without writing SQL CASE ladders.

Example

sql

SELECT * FROM pgrdf.sparql(
  'PREFIX foaf: <http://xmlns.com/foaf/0.1/>
   SELECT ?s ?n
     WHERE { ?s foaf:name ?n .
             ?s <http://example.com/age> ?age
             FILTER(?age >= 30 && REGEX(?n, "^A", "i")) }');

Term-type filter:

sql

SELECT * FROM pgrdf.sparql(
  'PREFIX foaf: <http://xmlns.com/foaf/0.1/>
   SELECT ?s ?o
     WHERE { ?s ?p ?o FILTER(isIRI(?o) && ?p = foaf:knows) }');

FILTER — boolean composition over solutions ​

What it does ​

Why you'd use it ​

Example ​

Tests ​

FILTER — boolean composition over solutions

What it does

Why you'd use it

Example

Tests