SPARQL 1.2 Features in Exocortex

Exocortex implements key features from the SPARQL 1.2 specification, extending the standard SPARQL 1.1 functionality with modern capabilities for RDF data management.

Overview
LATERAL Joins
PREFIX* Declarations
DESCRIBE Options
Directional Language Tags
DateTime Arithmetic
String Functions
RDF-Star Support

Overview

SPARQL 1.2 is the next evolution of the SPARQL query language, adding features that address common pain points in SPARQL 1.1. Exocortex implements the most impactful features:

Feature	Status	Description
LATERAL Joins	✅ Full	Correlated subqueries for "top N per group"
PREFIX*	✅ Full	Auto-import well-known prefixes
DESCRIBE Options	✅ Full	DEPTH and SYMMETRIC control
Directional Language Tags	✅ Full	RTL/LTR text direction support
DateTime Arithmetic	✅ Full	Date/time subtraction and duration operations
NORMALIZE/FOLD	✅ Full	Unicode normalization and case folding
RDF-Star	⚠️ Partial	Quoted triple data model support

LATERAL Joins

LATERAL joins enable correlated subqueries where the inner query can reference variables from the outer query. This enables patterns like "top N per group" that are not possible with standard subqueries.

Syntax

SELECT ?outer ?inner
WHERE {
  ?outer a :SomeClass .
  LATERAL {
    SELECT ?inner WHERE {
      ?outer :relates ?inner .  # References outer variable
    }
    ORDER BY DESC(?score)
    LIMIT 1
  }
}

Key Features

Inner query can reference variables bound in the outer query
Works with ORDER BY and LIMIT for "top N per group" patterns
Executed once per outer binding (correlated evaluation)
Inner join semantics (rows with no inner matches are excluded)

Example: Top Friend Per Person

Find each person's highest-scoring friend:

PREFIX : <http://example.org/>

SELECT ?person ?topFriend ?score
WHERE {
  ?person a :Person .
  LATERAL {
    SELECT ?topFriend ?score WHERE {
      ?person :knows ?topFriend .
      ?topFriend :score ?score .
    }
    ORDER BY DESC(?score)
    LIMIT 1
  }
}

Result:

person	topFriend	score
:alice	:charlie	95
:eve	:grace	90

Example: Top N Per Category

Get the top 2 tasks by votes for each project:

PREFIX exo: <https://exocortex.my/ontology/exo#>
PREFIX ems: <https://exocortex.my/ontology/ems#>

SELECT ?project ?task ?votes
WHERE {
  ?project exo:Instance_class "ems__Project" .
  LATERAL {
    SELECT ?task ?votes WHERE {
      ?task ems:belongs_to_project ?project .
      ?task ems:Effort_votes ?votes .
    }
    ORDER BY DESC(?votes)
    LIMIT 2
  }
}

Multiple LATERAL Patterns

You can chain multiple LATERAL patterns:

SELECT ?person ?friend ?project
WHERE {
  ?person a :Person .
  LATERAL {
    SELECT ?friend WHERE {
      ?person :knows ?friend .
    }
    LIMIT 1
  }
  LATERAL {
    SELECT ?project WHERE {
      ?person :worksOn ?project .
    }
    LIMIT 1
  }
}

PREFIX* Declarations

PREFIX* allows auto-importing prefixes from well-known vocabularies without manually declaring them.

Syntax

PREFIX* <http://schema.org/>
PREFIX* <http://xmlns.com/foaf/0.1/>

SELECT ?name WHERE {
  ?person schema:name ?name .
  ?person foaf:knows ?friend .
}

Supported Vocabularies

Vocabulary	Namespace	Auto-Prefix
Schema.org	`http://schema.org/`	`schema:`
FOAF	`http://xmlns.com/foaf/0.1/`	`foaf:`
Dublin Core	`http://purl.org/dc/elements/1.1/`	`dc:`, `dcterms:`
RDF	`http://www.w3.org/1999/02/22-rdf-syntax-ns#`	`rdf:`
RDFS	`http://www.w3.org/2000/01/rdf-schema#`	`rdfs:`
OWL	`http://www.w3.org/2002/07/owl#`	`owl:`
XSD	`http://www.w3.org/2001/XMLSchema#`	`xsd:`
SKOS	`http://www.w3.org/2004/02/skos/core#`	`skos:`
PROV	`http://www.w3.org/ns/prov#`	`prov:`
GEO	`http://www.w3.org/2003/01/geo/wgs84_pos#`	`geo:`
DCAT	`http://www.w3.org/ns/dcat#`	`dcat:`

Unknown Vocabularies

For unknown vocabularies, a fallback prefix is generated from the URI path:

PREFIX* <http://example.org/custom/ontology/>
# Generates: PREFIX ontology: <http://example.org/custom/ontology/>

DESCRIBE Options

SPARQL 1.2 adds DEPTH and SYMMETRIC options to DESCRIBE queries for fine-grained control over result generation.

Syntax

DESCRIBE ?resource DEPTH 2
DESCRIBE ?resource SYMMETRIC
DESCRIBE ?resource DEPTH 1 SYMMETRIC

Options

Option	Description	Default
`DEPTH n`	Limit description to n hops from resource	Unlimited (direct triples only)
`SYMMETRIC`	Include both incoming and outgoing triples	Already includes both

Example: Limited Depth

Describe a task with only direct properties:

DESCRIBE <vault://Tasks/My-Task.md> DEPTH 1

Example: Extended Description

Describe a task and related entities up to 2 hops:

PREFIX exo: <https://exocortex.my/ontology/exo#>

DESCRIBE ?task DEPTH 2
WHERE {
  ?task exo:Instance_class "ems__Task" .
  ?task exo:Asset_label "My Important Task" .
}

Directional Language Tags

SPARQL 1.2 supports directional language tags for bidirectional text (RTL/LTR).

Syntax

Language tags can include a direction suffix using --ltr or --rtl:

"مرحبا"@ar--rtl    # Arabic, right-to-left
"Hello"@en--ltr    # English, left-to-right
"שלום"@he--rtl     # Hebrew, right-to-left

LANGDIR Function

Get the complete language tag including direction:

SELECT ?text (LANGDIR(?text) AS ?langdir)
WHERE {
  ?s :label ?text .
}

Examples:

Input	LANGDIR Result
`"مرحبا"@ar--rtl`	`"ar--rtl"`
`"Hello"@en--ltr`	`"en--ltr"`
`"Hello"@en`	`"en"`
`"Hello"`	`""`

hasLANGDIR Function

Check if a literal has a direction:

SELECT ?text
WHERE {
  ?s :label ?text .
  FILTER(hasLANGDIR(?text))
}

Examples:

Input	hasLANGDIR Result
`"مرحبا"@ar--rtl`	`true`
`"Hello"@en`	`false`
`"Hello"`	`false`

STRLANGDIR Function

Create a directional literal:

SELECT (STRLANGDIR("مرحبا", "ar", "rtl") AS ?arabic)
WHERE {}

Signature: STRLANGDIR(lexicalForm, language, direction)

lexicalForm: The string value
language: Language tag (e.g., "ar", "en-US")
direction: "ltr" or "rtl"

Examples:

STRLANGDIR("Hello", "en", "ltr")  # → "Hello"@en--ltr
STRLANGDIR("مرحبا", "ar", "rtl")  # → "مرحبا"@ar--rtl

DateTime Arithmetic

SPARQL 1.2 adds native support for date/time subtraction and duration operations.

Date/DateTime Subtraction

Subtract two dates or datetimes to get a duration:

PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

SELECT ?start ?end (?end - ?start AS ?duration)
WHERE {
  ?task :startTime ?start .
  ?task :endTime ?end .
}

Duration Types

The system supports ISO 8601 duration formats:

Type	Format	Example
`xsd:dayTimeDuration`	`P[n]DT[n]H[n]M[n]S`	`P1DT2H30M`
`xsd:yearMonthDuration`	`P[n]Y[n]M`	`P1Y6M`

Duration Arithmetic Functions

dateSubtract - Subtract a duration from a date:

SELECT (dateSubtract("2025-01-22", "P7D") AS ?weekAgo)
WHERE {}
# Result: "2025-01-15"

dateSubtractYearMonth - Subtract year/month duration:

SELECT (dateSubtractYearMonth("2025-06-15", "P6M") AS ?sixMonthsAgo)
WHERE {}
# Result: "2024-12-15"

Real-World Example: Sleep Duration

Calculate average sleep duration from Exocortex data:

PREFIX exo: <https://exocortex.my/ontology/exo#>
PREFIX ems: <https://exocortex.my/ontology/ems#>

SELECT ?label ?start ?end
       (HOURS(?end) - HOURS(?start) +
        (MINUTES(?end) - MINUTES(?start)) / 60 AS ?hours)
WHERE {
  ?s exo:Asset_label ?label .
  FILTER(STRSTARTS(?label, "Поспать"))
  ?s ems:Effort_startTimestamp ?start .
  ?s ems:Effort_endTimestamp ?end .
}

String Functions

NORMALIZE Function

Unicode normalization for consistent string comparison:

SELECT (NORMALIZE("café") AS ?normalized)
WHERE {}

Normalization Forms:

Form	Description
`NFC`	Canonical Composition (default)
`NFD`	Canonical Decomposition
`NFKC`	Compatibility Composition
`NFKD`	Compatibility Decomposition

Examples:

NORMALIZE("café")           # NFC normalized
NORMALIZE("ﬁ", "NFKC")      # → "fi" (ligature decomposed)
NORMALIZE("Ω", "NFD")       # NFD normalized omega

FOLD Function

Unicode case folding for case-insensitive comparison:

SELECT ?name
WHERE {
  ?s :name ?name .
  FILTER(FOLD(?name) = FOLD("HELLO"))
}

Key Features:

Full Unicode case folding (not just ASCII)
Handles special cases like German ß → ss
Handles Greek sigma variations (Σ → σ)
Decomposes ligatures (ﬁ → fi)

Examples:

FOLD("Hello")    # → "hello"
FOLD("Straße")   # → "strasse"
FOLD("ΣΕΛΛΑΣ")   # → "σελλασ"
FOLD("ﬁle")      # → "file"

RDF-Star Support

Exocortex includes foundational support for RDF-Star (statements about statements).

QuotedTriple Data Model

The QuotedTriple class represents triples that can appear in subject or object position:

import { QuotedTriple, IRI } from 'exocortex';

// Create a quoted triple representing "Alice knows Bob"
const quotedTriple = new QuotedTriple(
  new IRI('http://example.org/alice'),
  new IRI('http://example.org/knows'),
  new IRI('http://example.org/bob')
);

// Serialize to RDF-Star Turtle syntax
console.log(quotedTriple.toString());
// Output: << <http://example.org/alice> <http://example.org/knows> <http://example.org/bob> >>

Intended Usage

RDF-Star enables metadata about statements:

# Standard RDF-Star syntax (planned)
<< :Alice :knows :Bob >> :source :Wikipedia .
<< :Alice :knows :Bob >> :confidence "0.95"^^xsd:decimal .

Current Status

Implemented:

QuotedTriple domain model class
Structural equality checking
Turtle serialization
Nested quoted triple support

Planned (Future Releases):

SPARQL functions: TRIPLE(), SUBJECT(), PREDICATE(), OBJECT(), isTRIPLE()
Parser support for << s p o >> syntax in SPARQL
Triple store support for quoted triples

Implementation Notes

Parser Pipeline

SPARQL 1.2 features that sparqljs doesn't support natively are handled via transformers:

LateralTransformer - Converts LATERAL { ... } to marked subqueries
PrefixStarTransformer - Expands PREFIX* to standard PREFIX declarations
DescribeOptionsTransformer - Extracts DEPTH/SYMMETRIC options
DirectionalLangTagTransformer - Processes @lang--dir syntax

Performance Considerations

LATERAL joins execute the inner query once per outer binding
PREFIX* resolution is cached for well-known vocabularies
DateTime arithmetic uses native JavaScript Date operations
NORMALIZE/FOLD use native JavaScript string methods with Unicode support

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SPARQL 1.2 Features in Exocortex

Table of Contents

Overview

LATERAL Joins

Syntax

Key Features

Example: Top Friend Per Person

Example: Top N Per Category

Multiple LATERAL Patterns

PREFIX* Declarations

Syntax

Supported Vocabularies

Unknown Vocabularies

DESCRIBE Options

Syntax

Options

Example: Limited Depth

Example: Extended Description

Directional Language Tags

Syntax

LANGDIR Function

hasLANGDIR Function

STRLANGDIR Function

DateTime Arithmetic

Date/DateTime Subtraction

Duration Types

Duration Arithmetic Functions

Real-World Example: Sleep Duration

String Functions

NORMALIZE Function

FOLD Function

RDF-Star Support

QuotedTriple Data Model

Intended Usage

Current Status

Implementation Notes

Parser Pipeline

Performance Considerations

Related Documentation

External References