Getting Started With Corese-library

This tutorial show how to use the Corese-library framework through simple examples of the main features. We assume a basic knowledge in Java programming and in semantic web.

The first part describes how to create, load and export a Graph. The second part show how to query a graph with SPARQL. The third part details how to validate a graph with the Shapes Constraint Language (SHACL). The fourth part shows how to transforme a graph with the extension language SPARQL Template Transformation Language (STTL). The fifth part details how to apply a set of rules on a graph using the SPARQL Rule extension language. Finally, the sixth part describes how to define and use functions with the LDScript extension language.

1. Installation

Installations instructions are available on the Corese-Command GitHub repository.

2. Graph

This section describes how to create a graph manually, load a graph from file and serialize a graph to file.

2.1. Build a Graph by program

It is also possible to use the RDF4J Model API to create and manipulate a graph.

The example shows how to create the RDF graph bellow:

graph LR; classDef IRI fill:#FEAE65,stroke-width:0px classDef DT fill:#FEFEFE,stroke-width:0px iri:EdithPiaf(["ex:EdithPiaf"]) iri:Singer(["ex:Singer"]) dt:Edith["''Edith''"] dt:Piaf["''Piaf''"] class iri:EdithPiaf,iri:Singer IRI class dt:Edith,dt:Piaf DT iri:EdithPiaf--rdf:type-->iri:Singer; iri:EdithPiaf--ex:firstName-->dt:Edith; iri:EdithPiaf--ex:lastName-->dt:Piaf;

This graph represents three statements :

• Edith Piaf is a singer

• Edith Piaf’s first name is Edith

• Edith Piaf’s last name is Piaf

// Define the namespace ex
String ex = "http://example.org/";

// Create a new empty Graph
Graph graph = Graph.create();

// Create and add IRIs to Graph
Node edithPiafIRI = graph.addResource(ex + "EdithPiaf");
Node singerIRI = graph.addResource(ex + "Singer");

// Create and add properties to Graph
Node rdfTypeProperty = graph.addProperty(RDF.TYPE);
Node firstNameProperty = graph.addProperty(ex + "firstName");
Node lastNameProperty = graph.addProperty(ex + "lastName");

// Create and add datatypes to Graph
Node edithDatatype = graph.addLiteral("Edith");
Node piafDatatype = graph.addLiteral("Piaf");

// Add first statement : Edith Piaf is an Singer
graph.addEdge(edithPiafIRI, rdfTypeProperty, singerIRI);
// Add second statement : Edith Piaf's first name is Edith
graph.addEdge(edithPiafIRI, firstNameProperty, edithDatatype);
// Add third statement : Edith Piaf's last name is Piaf
graph.addEdge(edithPiafIRI, lastNameProperty, piafDatatype);

2.2. Load Graph from file

This example shows how to load a graph from a file. Corese Loader can load formats :

• RDF/XML (.rdf)

• TURTLE (.ttl)

• TRIG (.trig)

• JSONLD (.jsonld)

• NTRIPLES (.nt)

• NQUADS (.nq)

• JSON-LD (.jsonld)

• RDFa (.html)

// Create a new empty Graph
Graph graph = Graph.create();

// Create loader and parse file
Load ld = Load.create(graph);
ld.parse("input graph file path");

2.3. Export Graph to file

This example shows how to serialize a graph in file, here in TURTLE format.

// We assume that the 'graph' variable has been define previously

// Create exporter
ResultFormat exporter = ResultFormat.create(graph, ResultFormat.TURTLE_FORMAT);
String result = exporter.toString();

// Write result in file
FileWriter writer = new FileWriter("output file path");
writer.write(result);
writer.close();

Corese Transformer can serialize graphs in different formats :

• RDF/XML ResultFormat.RDF_XML_FORMAT

• TURTLE ResultFormat.TURTLE_FORMAT

• TRIG ResultFormat.TRIG_FORMAT

• JSONLD ResultFormat.JSONLD_FORMAT

• NTRIPLES ResultFormat.NTRIPLES_FORMAT

• NQUADS ResultFormat.NQUADS_FORMAT

3. SPARQL Protocol and RDF Query Language

This section describes how to query a graph with SPARQL in Corese.

3.1. SPARQL Select query

This example shows how to execute a SPARQL SELECT query, print and export results.

// We assume that the 'graph' variable has been define previously

// Sparql query
QueryProcess exec = QueryProcess.create(graph);
Mappings map = exec.query("select * where { ?s ?p ?o }");

Example of how to get a variable value in the results:

// Iterate on each result
for (Mapping m : map) {
    // Get the value of the variable ?o
    IDatatype dt = m.getValue("?o");

    // Test and convert the value to java type
    if (dt.isURI()) {
        String uriLabel = dt.getLabel();
    }
    else if (dt.isBlank()) {
        String BNLabel = dt.getLabel();
    }
    else {
        if (dt.isBoolean()) {
            boolean boolResult = dt.booleanValue();
        }
        else if (dt.isNumber()) {
            int intResult = dt.intValue();
            double doubleResult = dt.doubleValue();
            float floatResult = dt.floatValue();
            BigDecimal bigDecimalResult = dt.decimalValue();
            long longResult = dt.longValue();
        }
        else {
            String stringResult = dt.stringValue();
            String stringLangResult = dt.getLang();
        }
    }
}

Print list of variables in the result:

System.out.println(map.getSelect());
// Exemple: ["?s", "?p", "?o"]

Print results:

for (Mapping m: map){
    System.out.println(m);
}

Export result in XML:

ResultFormat result_xml = ResultFormat.create(map);
result_xml.write("output file path");

3.2. SPARQL Ask query

This example shows how to execute a SPARQL ASK query and print results.

// We assume that the 'graph' variable has been define previously

// Sparql query
QueryProcess exec = QueryProcess.create(graph);
Mappings map = exec.query("ask { ?person foaf:name ?name. }");

Print results:

// if the mappings is empty then the result is false
// if the mappings is not empty then the result is true
system.out.println(!map.isEmpty());

3.3. SPARQL Construct query

// We assume that the 'graph' variable has been define previously

// Sparql query
QueryProcess exec = QueryProcess.create(graph);
Mappings map = exec.query("""
    prefix foaf: <http://xmlns.com/foaf/0.1/>
    prefix vcard: <http://www.w3.org/2001/vcard-rdf/3.0#>

    construct {
        ?person vcard:FN ?name
    }
    where {
        ?person foaf:name ?name.
    }
    """
);

Print graph result of a construct-where query :

Graph g = (Graph) map.getGraph();
Graph result_graph = (Graph) map.getGraph();
System.out.println(result_graph.display());

Export result in XML:

// Export result in XML
ResultFormat result_xml = ResultFormat.create(map);
result_xml.write("output file path");

3.4. SPARQL Update query

// We assume that the 'graph' variable has been define previously

// Sparql query
QueryProcess exec = QueryProcess.create(graph);
exec.query("""
    prefix foaf: <http://xmlns.com/foaf/0.1/>
    prefix vcard: <http://www.w3.org/2001/vcard-rdf/3.0#>

    insert {
        ?person vcard:FN ?name
    }
    where {
        ?person foaf:name ?name.
    }
    """
);

4. Shapes Constraint Language (SHACL)

This section show how to validate a graph with the Shapes Constraint Language (SHACL) in Corese. The example below shows us how to load a shapes graph (SHACL file), check the validity of the data graph and finally print results.

// Load data graph
Graph dataGraph = Graph.create();
Load ld = Load.create(dataGraph);
ld.parse("input graph file path");

// Load shape graph
Graph shapeGraph = Graph.create();
ld = Load.create(shapeGraph);
ld.parse("input shape file path.ttl");

// Evaluation
Shacl shacl = new Shacl(dataGraph, shapeGraph);
Graph result = shacl.eval();

// print results
Transformer transformer = Transformer.create(result, Transformer.TURTLE);
System.out.println(transformer.toString());

Input graph file path:

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

ex:Alice ex:ssn "987-65-4323" ;
    ex:worksFor ex:Haribo, ex:KitKat ;
    rdf:type ex:Person .

ex:Bob ex:ssn "124-35-6789" ;
    ex:worksFor ex:Twitch ;
    rdf:type ex:Person .

ex:Calvin ex:ssn "648-67-6545" ;
    ex:worksFor ex:UntypedCompany ;
    rdf:type ex:Person .

ex:Haribo rdf:type ex:Company .

ex:KitKat rdf:type ex:Company .

ex:Twitch rdf:type ex:Company .

ex:UntypedCompany rdf:type ex:Company .

Input shape file path:

@prefix sh: <http://www.w3.org/ns/shacl#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix ex: <http://example.org/ns#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

ex:PersonShape
    a sh:NodeShape ;
    sh:targetClass ex:Person ;
    sh:property [
        sh:path ex:ssn ;
        sh:maxCount 1 ;
        sh:datatype xsd:string ;
        sh:pattern "^\\d{3}-\\d{2}-\\d{4}$" ;
    ] ;
    sh:property [
        sh:path ex:worksFor ;
        sh:class ex:Company ;
        sh:nodeKind sh:IRI ;
    ] ;
    sh:closed true ;
    sh:ignoredProperties ( rdf:type ) .

Result:

@prefix xsh: <http://www.w3.org/ns/shacl#> .
@prefix sh: <http://www.w3.org/ns/shacl#> .

[a sh:ValidationReport ;
    sh:conforms true] .

5. SPARQL Template Transformation Language (STTL)

This sections shows how to transforme a graph with a subset of the extension language SPARQL Template Transformation Language (STTL).

5.1. Transform a graph in a visual HTML format

This example detail how load a data graph from a file, transforme it in a visual HTML format and export the result in a file.

// Open template file
Path path = Path.of("input template file path");
String sttl_query = Files.readString(path, StandardCharsets.UTF_8);

// Load data graph
Graph dataGraph = Graph.create();
Load ld = Load.create(dataGraph);
ld.parse("input graph file path");

// Apply STTL query
QueryProcess exec = QueryProcess.create(dataGraph);
Mappings map = exec.query(sttl_query);

// Export result
ResultFormat result_xml = ResultFormat.create(map);
result_xml.write("output file path");

Input template file:

template {
    format {
        "<html>\n\n<body>\n\t<table>\n%s\t</table>\n</body>\n\n</html>"
        group {
            format {
                "\t\t<tr>\n\t\t\t<td>%s</td>\n\t\t\t<td>%s</td>\n\t\t\t<td>%s</td>\n\t\t</tr>\n"
                ?s ?p ?o
            }
        }
    }
}
where {
    ?s ?p ?o
}
order by ?s ?p ?o

Result :

<html>

<body>
    <table>
        <tr>
            <td>http://example.org/EdithPiaf</td>
            <td>http://example.org/firstName</td>
            <td>Edith</td>
        </tr>
        <tr>
            <td>http://example.org/EdithPiaf</td>
            <td>http://example.org/lastName</td>
            <td>Piaf</td>
        </tr>
        <tr>
            <td>http://example.org/EdithPiaf</td>
            <td>http://www.w3.org/1999/02/22-rdf-syntax-ns#type</td>
            <td>http://example.org/Singer</td>
        </tr>
    </table>
</body>

</html>

?s	?p	?o
http://example.org/EdithPiaf	http://example.org/firstName	Edith
http://example.org/EdithPiaf	http://example.org/lastName	Piaf
http://example.org/EdithPiaf	http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://example.org/Singer

6. SPARQL Rule

This section details how to apply a set of rules on a graph using the SPARQL Rule extension language.

6.1. Load rules from a file

The example below shows the application of two rules (symmetry and transitivity) on a simple graph.

// Create and load data in a graph
Graph dataGraph = Graph.create();
Load dataLoader = Load.create(dataGraph);
dataLoader.parse("input graph file path");


// Create and load rules into a rules engine
RuleEngine ruleEngine = RuleEngine.create(dataGraph);
RuleLoad ruleLoader = RuleLoad.create(ruleEngine);
ruleLoader.parse("input rules file path.rul");


// Apply rules on graph
ruleEngine.process();

Original graph:

graph LR; classDef IRI fill:#FEAE65,stroke-width:0px iri:alice(["ex:Alice"]) iri:bob(["ex:Bob"]) iri:camille(["ex:Camille"]) iri:daniel(["ex:Daniel"]) iri:elise(["ex:Elise"]) class iri:alice,iri:bob,iri:camille,iri:daniel,iri:elise IRI iri:alice--ex:friend-->iri:bob; iri:bob--ex:friend-->iri:camille; iri:daniel--ex:isMarriedTo-->iri:elise;

Rules file:

• Symmetry : if exist X➝Y then Y➝X

• Transitivity : if X➝Y➝Z then X➝Z

<?xml version="1.0"?>

<rdf:RDF
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns="http://ns.inria.fr/corese/rule/">

    <rule>
        <body>
            <![CDATA[
                prefix owl: <http://www.w3.org/2002/07/owl#>
                construct {
                    ?x ?p ?z
                }
                where {
                    ?p a owl:TransitiveProperty .
                    ?x ?p ?y .
                    ?y ?p ?z
                }
            ]]>
        </body>
    </rule>

    <rule>
        <body>
            <![CDATA[
                prefix owl: <http://www.w3.org/2002/07/owl#>
                construct {
                   ?y ?p ?x
                }
                where {
                    ?p a owl:SymmetricProperty .
                    ?x ?p ?y .
                }
            ]]>
        </body>
    </rule>

</rdf:RDF>

Result graph:

graph LR; classDef IRI fill:#FEAE65,stroke-width:0px iri:alice(["ex:Alice"]) iri:bob(["ex:Bob"]) iri:camille(["ex:Camille"]) iri:daniel(["ex:Daniel"]) iri:elise(["ex:Elise"]) class iri:alice,iri:bob,iri:camille,iri:daniel,iri:elise IRI iri:alice--ex:friend-->iri:bob; iri:bob--ex:friend-->iri:camille; iri:alice-.ex:friend.->iri:camille; iri:daniel--ex:isMarriedTo.->iri:elise; iri:elise-.ex:isMarriedTo.->iri:daniel; linkStyle 4,2 stroke:#a3ddcb,stroke-width:3px;

6.2. OWL Rules

The example below shows the application of OWL RL rules.

// We assume that the 'graph' variable has been define previously

// Apply rules
RuleEngine engine = RuleEngine.create(graph);
engine.setProfile(RuleEngine.OWL_RL);
engine.process();

7. LDScript

This section describes how to define and use functions with the LDScript extension language.

7.1. Fibonacci function call from Java

This example shows how to define and compute the twelfth number of the Fibonnacci sequence.

// Open LDScript file
Path path = Path.of("input LDScript file path.rq");
String ldScript = Files.readString(path, StandardCharsets.UTF_8);

// Compile LDScript
QueryProcess exec = QueryProcess.create();
exec.compile(ldScript);

// Compute the twelfth number of the Fibonnacci sequence
String name = "http://ns.inria.fr/fibonacci";
IDatatype dt = exec.funcall(name, DatatypeMap.newInstance(25));

// Print result
System.out.println(dt);

Input LDScript file path:

prefix fun: <http://ns.inria.fr/>

@public function fun:fibonacci(n) {
    if (n < 0) {
        error()
    }
    else if (n = 0) {
        return(0)
    }
    else if (n = 1) {
        return(1)
    }
    else {
        return (fun:fibonacci(n - 1) + fun:fibonacci(n - 2))
    }
}

7.2. LDScript in SPARQL

This example shows how to call an LDScript function from a SPARQL query.

String check_query = """
prefix ex: <http://example.com/city/>
prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
prefix fun: <http://ns.inria.fr/>

select ?name ?area
where {
    ?city rdf:type ex:city ;
            ex:name ?name ;
            ex:area ?area .
    filter(?area > fun:toSquareKm(40))
}

# Convert square mile to square Kilometer
function fun:toSquareKm(squareMile) {
    return (squareMile * 2.59)
}
""";


// Load graph
Graph graph = Graph.create();
Load ld = Load.create(graph);
ld.parse("input file path");

// Sparql query
QueryProcess exec = QueryProcess.create(graph);
Mappings map = exec.query(check_query);

7.3. Advanced example

The java program below computes the percentage of people subscribed to social networks of city compared to its number of inhabitants. Data is collected from Wikidata.

// Open LDScript file
Path path = Path.of("input LDScript file path.rq");
String ldScript = Files.readString(path, StandardCharsets.UTF_8);

// Compile LDScript
QueryProcess exec = QueryProcess.create();
exec.compile(ldScript);

// Execute program
String name = "http://ns.inria.fr/main";
IDatatype dt = exec.funcall(name);

// Print result
System.out.println(dt);

Input LDScript file path:

prefix fun: <http://ns.inria.fr/>

prefix wd: <http://www.wikidata.org/entity/>
prefix wdt: <http://www.wikidata.org/prop/direct/>
prefix wikibase: <http://wikiba.se/ontology#>
prefix bd: <http://www.bigdata.com/rdf#>
prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>


@public
function fun:percentage(sub, total) {
    return (sub / total * 100)
}

@public
function fun:citypopulationsocialmedia() {

    query(
        select ?city ?citylabel ?population ?socialmediafolower where {
            service <https://query.wikidata.org/sparql> {
                ?city wdt:P31 wd:Q1549591;
                wdt:P8687 ?socialmediafolower;
                wdt:P1082 ?population.
                optional {
                    ?city rdfs:label ?citylabel
                    filter (lang(?citylabel) = "en").
                }
            }
        }
        order by desc (?socialmediafolower)
        limit 100
    )
}

@public
function fun:main() {
    xt:sort(
        maplist (
            function(x) {
                let ((citylabel population socialmediafolower) = x) {
                    return (xt:list(citylabel, fun:percentage(socialmediafolower, population)))
                }
            },
            fun:citypopulationsocialmedia()
        ),
        function(x,y)  {
            let ((x_name, x_value) = x, (y_name, y_value) = y) {
                if (x_value < y_value, 1, if(x=y, o, -1))
            }
        }
    )
}