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A RDF-based vocabulary to model SPARQL queries into RDF. SPARQL queries can thus be represented, queried, generated, validated, analysed, transformed and reused as semantic objects themselves.

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sparqlvoc

A RDF-based vocabulary to model SPARQL queries into RDF. Sparqlvoc offers OWL-classes, properties and SHACL shapes, with which SPARQL queries can be represented, queried, generated, validated, analysed, transformed and reused. With Sparqlvoc SPARQL queries themselves become semantic objects worthy of inspection.

Abstract

The SPARQL Vocabulary provides a RDF-based formal representation of the SPARQL query language according to the SPARQL 1.1 specification https://www.w3.org/TR/sparql11-query/. It leverages modeling and generation of SPARQL queries through an abstract syntax tree (AST) framework. To this end, the vocabulary defines classes and properties to describe the various components of SPARQL queries, including SELECT, WHERE, FILTER, and UNION constructs. Additionally, it incorporates SHACL shapes for validating SPARQL query structures and supports algorithms for serializing SPARQL queries from RDF representations. This vocabulary enhances semantic data retrieval and management, bridging SPARQL with broader semantic web technologies.

Description

The SPARQL Vocabulary formalizes the SPARQL query language, offering a structured representation of its syntax and semantics. The vocabulary models the SPARQL query language as an abstract syntax tree, consisting of the following nodes in a tree:

  • tree
    • node
      • non-terminal node
      • terminal node
        • keyword
        • symbol
        • symbol sequence
        • character sequence

As a source for the model we use the grammar from the SPARQL 1.1 specification: https://www.w3.org/TR/sparql11-query/#grammar.

The vocabulary defines classes for different SPARQL query components, such as 'sparql:SelectQuery' for SELECT queries, 'sparql:WhereClause' for WHERE clauses, and properties to capture relationships between these components. Central to this vocabulary is the class 'sparql:QueryUnit', which serves as a building block for all types of queries. All SPARQL building blocks are in a way connected to this root node in the abstract syntax tree of SPARQL. Each query component is associated with a fragment of a SPARQL query. The fragment itself is modeled though the datatype property sparql:fragment, connected to each node of the tree. The vocabulary also includes SHACL shapes to validate the correctness of SPARQL query structures, ensuring that generated queries conform to the syntax rules of SPARQL. The SPARQL Vocabulary offers five algorithms captured in five SHACL nodeshapes to generate an actual SPARQL query based on its RDF-based abstract syntax tree. These five algorithms align with the above mentioned model of the abstract syntax tree and its components.

  1. shp:NonTerminalNode
  2. shp:Keyword
  3. shp:Symbol
  4. shp:SymbolSequence
  5. shp:CharacterSequence

These shapes allow for the creation of well-formed queries that can be efficiently executed against RDF data stores. This comprehensive approach facilitates the generation of SPARQL queries from RDF representations, allowing users to leverage semantic technologies for effective data querying and retrieval.

Introduction

In the rapidly evolving landscape of semantic web technologies, the ability to query and manipulate RDF data effectively is paramount. As organizations seek to harness the power of linked data and knowledge graphs, they encounter the need for robust frameworks that facilitate the creation, validation, and execution of SPARQL queries. The SPARQL Vocabulary addresses this necessity by providing a structured approach to model and generate SPARQL queries through an abstract syntax tree representation, enhancing the agility and precision of data retrieval operations.

Background

Organizations today are inundated with data from a multitude of sources, necessitating effective querying techniques to extract meaningful insights. The complexity of SPARQL, with its various query forms and constructs, presents challenges for users seeking to create well-structured queries. As the demand for semantic interoperability and linked data increases, there is a pressing need for frameworks that facilitate SPARQL query generation while ensuring adherence to semantic web standards. The SPARQL Vocabulary meets these challenges head-on, offering a formalized structure for both novice and experienced users to construct SPARQL queries with confidence.

Objective

To address the challenges of SPARQL query generation and validation, we introduce the SPARQL Vocabulary - a transformative framework designed to empower users in mastering SPARQL query creation. This vocabulary enables users to (1) model and represent SPARQL query constructs, (2) generate and validate SPARQL queries programmatically, and (3) ensure compliance with SPARQL syntax rules. By leveraging the power of RDF and the flexibility of an abstract syntax tree, the SPARQL Vocabulary enhances the efficiency and accuracy of data retrieval in semantic web applications, fostering greater insights from linked data resources.

Audience

This document is intended for a diverse audience of software developers, data scientists, semantic web practitioners, and anyone involved in querying and managing RDF data. It aims to support users seeking to enhance their understanding and application of SPARQL within the context of semantic technologies.

Status

Unstable & unfinished. Work in progress.

Simple example

BASE <https:example.org/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT *
WHERE { ?s ?p ?o }

Modeled as:

prefix ex: <https://www.example.org/>
prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
prefix sparql: <http://www.w3.org/ns/sparql#model/def/>

ex:exampleQueryTree
                rdf:type sparql:AbstractSyntaxTree;
                rdf:_1   ex:exampleQuery.

ex:exampleQuery 
                rdf:type sparql:QueryUnit;
                rdf:_1 ex:prologue;
                rdf:_2 ex:selectQuery.
                
ex:prologue 
                rdf:type sparql:Prologue;
                rdf:_1 ex:baseDecl;
                rdf:_2 ex:prefixDecl.
               
ex:baseDecl 
                rdf:type sparql:BaseDecl;
                rdf:_1 ex:base;              
                rdf:_2 ex:iriRefBase.

ex:base
                rdf:type sparql:Base.

ex:iriRefBase 
                rdf:type sparql:IRIRef;
                rdf:_1 ex:lessThan;
                rdf:_2 ex:iriValue_Base;
                rdf:_3 ex:greaterThan.

ex:lessThan
                rdf:type sparql:LessThan.

ex:greaterThan
                rdf:type sparql:GreaterThan.
                              
ex:iriValue_Base
                rdf:type sparql:CharacterSequence;
                rdf:value "https://example.org/".
                
ex:prefixDecl    
                rdf:type sparql:PrefixDecl;
                rdf:_1 ex:prefix;
                rdf:_2 ex:pname_NS;
                rdf:_3 ex:iriRef_RDF.

ex:prefix
                rdf:type sparql:Prefix.

ex:pname_NS   
                rdf:type sparql:PNAME_NS;
                rdf:_1 ex:pn_prefix_RDF;
                rdf:_2 ex:colon.
                
ex:pn_prefix_RDF 
                rdf:type sparql:PN_PREFIX;
                rdf:_1 ex:pn_chars_base_RDF.
                

ex:pn_chars_base_RDF
                rdf:type sparql:PN_CHARS_BASE;
                rdf:value "rdf".

ex:colon
                rdf:type sparql:Colon.
                
ex:iriRef_RDF 
                rdf:type sparql:IRIRef;
                rdf:_1 ex:lessThan;
                rdf:_2 ex:iriValue_RDF;
                rdf:_3 ex:greaterThan.

ex:iriValue_RDF
                rdf:type sparql:CharacterSequence;
                rdf:value "http://www.w3.org/1999/02/22-rdf-syntax-ns#".

ex:selectQuery
                rdf:type sparql:SelectQuery;
                rdf:_1 ex:selectClause1;
                rdf:_2 ex:whereClause1.
                
ex:selectClause1
                rdf:type sparql:SelectClause;
                rdf:_1 ex:select;
                rdf:_2 ex:wildcard.

ex:select
                rdf:type sparql:Select.
                
ex:wildcard 
                rdf:type sparql:Wildcard.

ex:whereClause1 
                rdf:type sparql:WhereClause;
                rdf:_1 ex:where;
                rdf:_2 ex:groupGraphPattern.

ex:where
                rdf:type sparql:Where.

ex:groupGraphPattern
                rdf:type sparql:GroupGraphPattern;
                rdf:_1 ex:openCurlyBracket ;
                rdf:_2 ex:groupGraphPatternSub ;
                rdf:_3 ex:closedCurlyBracket.

ex:openCurlyBracket 
                rdf:type sparql:OpenCurlyBracket.

ex:closedCurlyBracket
                rdf:type sparql:ClosedCurlyBracket.
                
ex:groupGraphPatternSub
                rdf:type sparql:GroupGraphPatternSub;
                rdf:_1 ex:triplesBlock.
                
ex:triplesBlock
                rdf:type sparql:TriplesBlock;
                rdf:_1 ex:triplesSameSubjectPath.

ex:triplesSameSubjectPath
                rdf:type sparql:TriplesSameSubjectPath;
                rdf:_1 ex:varOrTerm1;
                rdf:_2 ex:propertyListPathNotEmpty.
                
ex:varOrTerm1
                rdf:type sparql:VarOrTerm;
                rdf:_1 ex:variable_s.

ex:variable_s
                rdf:type sparql:Variable;
                rdf:_1 ex:variable1_s.

ex:variable1_s                
                rdf:type sparql:Variable1;
                rdf:_1 ex:questionMark;
                rdf:_2 ex:variable1_s_name.

ex:questionMark
                rdf:type sparql:QuestionMark.

ex:variable1_s_name 
                rdf:type sparql:CharacterSequence;
                rdf:value 's'.
                
ex:propertyListPathNotEmpty
                rdf:type sparql:PropertyListPathNotEmpty;
                rdf:_1 ex:verbSimple;
                rdf:_2 ex:objectListPath.

ex:verbSimple 
                rdf:type sparql:VerbSimple;
                rdf:_1 ex:variable_p.

ex:variable_p
                rdf:type sparql:Variable;
                rdf:_1 ex:variable1_p.                    

ex:variable1_p
                rdf:type sparql:Variable1;
                rdf:_1 ex:questionMark;
                rdf:_2 ex:variable1_p_name.  
                
ex:variable1_p_name 
                rdf:type sparql:CharacterSequence;
                rdf:value 'p'.   
                
ex:objectListPath
                rdf:type sparql:ObjectListPath;
                rdf:_1 ex:objectPath.

ex:objectPath
                rdf:type sparql:ObjectPath;
                rdf:_1 ex:graphNodePath.

ex:graphNodePath 
                rdf:type sparql:GraphNodePath;
                rdf:_1 ex:varOrTerm2.
                
ex:varOrTerm2
                rdf:type sparql:VarOrTerm;
                rdf:_1 ex:variable_o.

ex:variable_o
                rdf:type sparql:Variable;
                rdf:_1 ex:variable1_o.

ex:variable1_o
                rdf:type sparql:Variable1;
                rdf:_1 ex:questionMark;
                rdf:_2 ex:variable1_o_name.                   

ex:variable1_o_name 
                rdf:type sparql:CharacterSequence;
                rdf:value 'o'.

Extended example - Filter clause

BASE <https://example.org/> 
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> 
SELECT * WHERE { ?s ?p ?o 
FILTER ( ?s = ?o ) }

This example makes use, through the FILTER keyword, of the expressions component in SPARQL.

This is modeled as:

prefix ex: <https://www.example.org/>
prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
prefix sparql: <http://www.w3.org/ns/sparql#model/def/>

ex:exampleQueryTree
                rdf:type sparql:AbstractSyntaxTree;
                rdf:_1   ex:exampleQuery.

ex:exampleQuery 
                rdf:type sparql:QueryUnit;
                rdf:_1 ex:prologue;
                rdf:_2 ex:selectQuery.
                
ex:prologue 
                rdf:type sparql:Prologue;
                rdf:_1 ex:baseDecl;
                rdf:_2 ex:prefixDecl.
               
ex:baseDecl 
                rdf:type sparql:BaseDecl;
                rdf:_1 ex:base;              
                rdf:_2 ex:iriRefBase.

ex:base
                rdf:type sparql:Base.

ex:iriRefBase 
                rdf:type sparql:IRIRef;
                rdf:_1 ex:lessThan;
                rdf:_2 ex:iriValue_Base;
                rdf:_3 ex:greaterThan.

ex:lessThan
                rdf:type sparql:LessThan.

ex:greaterThan
                rdf:type sparql:GreaterThan.
                              
ex:iriValue_Base
                rdf:type sparql:CharacterSequence;
                rdf:value "https://example.org/".
                
ex:prefixDecl    
                rdf:type sparql:PrefixDecl;
                rdf:_1 ex:prefix;
                rdf:_2 ex:pname_NS;
                rdf:_3 ex:iriRef_RDF.

ex:prefix
                rdf:type sparql:Prefix.

ex:pname_NS   
                rdf:type sparql:PNAME_NS;
                rdf:_1 ex:pn_prefix_RDF;
                rdf:_2 ex:colon.
                
ex:pn_prefix_RDF 
                rdf:type sparql:PN_PREFIX;
                rdf:_1 ex:pn_chars_base_RDF.
                

ex:pn_chars_base_RDF
                rdf:type sparql:PN_CHARS_BASE;
                rdf:value "rdf".

ex:colon
                rdf:type sparql:Colon.
                
ex:iriRef_RDF 
                rdf:type sparql:IRIRef;
                rdf:_1 ex:lessThan;
                rdf:_2 ex:iriValue_RDF;
                rdf:_3 ex:greaterThan.

ex:iriValue_RDF
                rdf:type sparql:CharacterSequence;
                rdf:value "http://www.w3.org/1999/02/22-rdf-syntax-ns#".

ex:selectQuery
                rdf:type sparql:SelectQuery;
                rdf:_1 ex:selectClause1;
                rdf:_2 ex:whereClause1.
                
ex:selectClause1
                rdf:type sparql:SelectClause;
                rdf:_1 ex:select;
                rdf:_2 ex:wildcard.

ex:select
                rdf:type sparql:Select.
                
ex:wildcard 
                rdf:type sparql:Wildcard.

ex:whereClause1 
                rdf:type sparql:WhereClause;
                rdf:_1 ex:where;
                rdf:_2 ex:groupGraphPattern.

ex:where
                rdf:type sparql:Where.

ex:groupGraphPattern
                rdf:type sparql:GroupGraphPattern;
                rdf:_1 ex:openCurlyBracket ;
                rdf:_2 ex:groupGraphPatternSub ;
                rdf:_3 ex:graphPatternNotTriples;
                rdf:_4 ex:closedCurlyBracket.

ex:openCurlyBracket 
                rdf:type sparql:OpenCurlyBracket.

ex:closedCurlyBracket
                rdf:type sparql:ClosedCurlyBracket.
                
ex:groupGraphPatternSub
                rdf:type sparql:GroupGraphPatternSub;
                rdf:_1 ex:triplesBlock.

ex:graphPatternNotTriples
                rdf:type sparql:GraphPatternNotTriples;
                rdf:_1 ex:filterClause.

ex:filterClause
                rdf:type sparql:FilterClause;
                rdf:_1 ex:filter;
                rdf:_2 ex:constraint.

ex:filter
                rdf:type sparql:Filter.
                
ex:constraint
                rdf:type sparql:Constraint;
                rdf:_1 ex:brackettedExpression.

ex:brackettedExpression
                rdf:type sparql:BrackettedExpression;
                rdf:_1 ex:openParenthesis;
                rdf:_2 ex:expression;
                rdf:_3 ex:closedParenthesis.

ex:openParenthesis
                rdf:type sparql:OpenParenthesis.
                
ex:closedParenthesis
                rdf:type sparql:ClosedParenthesis.

ex:expression
                rdf:type sparql:Expression;
                rdf:_1 ex:conditionalOrExpression.

ex:conditionalOrExpression
                rdf:type sparql:ConditionalOrExpression;
                rdf:_1 ex:conditionalAndExpression.

ex:conditionalAndExpression
                rdf:type sparql:ConditionalAndExpression;
                rdf:_1 ex:valueLogical.
                
ex:valueLogical
                rdf:type sparql:ValueLogical;
                rdf:_1 ex:relationalExpression.
                
ex:relationalExpression
                rdf:type sparql:RelationalExpression;
                rdf:_1 ex:numericExpression1;
                rdf:_2 ex:equal;
                rdf:_3 ex:numericExpression2.

ex:numericExpression1
                rdf:type sparql:NumericExpression;
                rdf:_1 ex:additiveExpression1.

ex:additiveExpression1
                rdf:type sparql:AdditiveExpression;
                rdf:_1 ex:multiplicativeExpression1.

ex:multiplicativeExpression1
                rdf:type sparql:MultiplicativeExpression;
                rdf:_1 ex:unaryExpression1.

ex:unaryExpression1
                rdf:type sparql:UnaryExpression;
                rdf:_1 ex:primaryExpression1.

ex:primaryExpression1
                rdf:type sparql:PrimaryExpression;
                rdf:_1 ex:variable_s.

ex:equal
                rdf:type sparql:Equal.

ex:numericExpression2
                rdf:type sparql:NumericExpression;
                rdf:_2 ex:additiveExpression2.

ex:additiveExpression2
                rdf:type sparql:AdditiveExpression;
                rdf:_2 ex:multiplicativeExpression2.

ex:multiplicativeExpression2
                rdf:type sparql:MultiplicativeExpression;
                rdf:_2 ex:unaryExpression2.

ex:unaryExpression2
                rdf:type sparql:UnaryExpression;
                rdf:_2 ex:primaryExpression2.

ex:primaryExpression2
                rdf:type sparql:PrimaryExpression;
                rdf:_2 ex:variable_o.
                
ex:triplesBlock
                rdf:type sparql:TriplesBlock;
                rdf:_1 ex:triplesSameSubjectPath.

ex:triplesSameSubjectPath
                rdf:type sparql:TriplesSameSubjectPath;
                rdf:_1 ex:varOrTerm1;
                rdf:_2 ex:propertyListPathNotEmpty.
                
ex:varOrTerm1
                rdf:type sparql:VarOrTerm;
                rdf:_1 ex:variable_s.

ex:variable_s
                rdf:type sparql:Variable;
                rdf:_1 ex:variable1_s.

ex:variable1_s                
                rdf:type sparql:Variable1;
                rdf:_1 ex:questionMark;
                rdf:_2 ex:variable1_s_name.

ex:questionMark
                rdf:type sparql:QuestionMark.

ex:variable1_s_name 
                rdf:type sparql:CharacterSequence;
                rdf:value 's'.
                
ex:propertyListPathNotEmpty
                rdf:type sparql:PropertyListPathNotEmpty;
                rdf:_1 ex:verbSimple;
                rdf:_2 ex:objectListPath.

ex:verbSimple 
                rdf:type sparql:VerbSimple;
                rdf:_1 ex:variable_p.

ex:variable_p
                rdf:type sparql:Variable;
                rdf:_1 ex:variable1_p.                    

ex:variable1_p
                rdf:type sparql:Variable1;
                rdf:_1 ex:questionMark;
                rdf:_2 ex:variable1_p_name. 
 
ex:variable1_p_name 
                rdf:type sparql:CharacterSequence;
                rdf:value 'p'.   
                
ex:objectListPath
                rdf:type sparql:ObjectListPath;
                rdf:_1 ex:objectPath.

ex:objectPath
                rdf:type sparql:ObjectPath;
                rdf:_1 ex:graphNodePath.

ex:graphNodePath 
                rdf:type sparql:GraphNodePath;
                rdf:_1 ex:varOrTerm2.
                
ex:varOrTerm2
                rdf:type sparql:VarOrTerm;
                rdf:_1 ex:variable_o.

ex:variable_o
                rdf:type sparql:Variable;
                rdf:_1 ex:variable1_o.

ex:variable1_o
                rdf:type sparql:Variable1;
                rdf:_1 ex:questionMark;
                rdf:_2 ex:variable1_o_name.     
                   
ex:variable1_o_name 
                rdf:type sparql:CharacterSequence;
                rdf:value 'o'.

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A RDF-based vocabulary to model SPARQL queries into RDF. SPARQL queries can thus be represented, queried, generated, validated, analysed, transformed and reused as semantic objects themselves.

Topics

sparql rdf owl sparql-query sparql-query-builder shacl

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