GH-5327 RDF 1.2 implementation for JSON and dirLangString literals

Author: SarahGrand

core/model-api/src/main/java/org/eclipse/rdf4j/model/Literal.java

@@ -41,6 +41,35 @@
  * @see <a href="https://www.w3.org/TR/xmlschema11-2">XML Schema Definition Language (XSD) 1.1 Part 2: Datatypes</a>
  */
 public interface Literal extends Value {
+	String LTR_SUFFIX = "--ltr";
+	String RTL_SUFFIX = "--rtl";
+	String BASE_DIR_SEPARATOR = "--";
+
+	enum BaseDirection {
+		NONE(""),
+		LTR(LTR_SUFFIX),
+		RTL(RTL_SUFFIX);
+
+		private final String suffix;
+
+		BaseDirection(final String suffix) {
+			this.suffix = suffix;
+		}
+
+		public String toString() {
+			return suffix;
+		}
+
+		public static BaseDirection fromString(String dir) {
+			if (dir == null || dir.isEmpty())
+				return NONE;
+			if (dir.equals(LTR_SUFFIX))
+				return LTR;
+			if (dir.equals(RTL_SUFFIX))
+				return RTL;
+			throw new IllegalArgumentException("Unknown BaseDirection: " + dir);
+		}
+	}
 
 	@Override
 	default boolean isLiteral() {
@@ -61,6 +90,10 @@ default boolean isLiteral() {
 	 */
 	Optional<String> getLanguage();
 
+	default BaseDirection getBaseDirection() {
+		return BaseDirection.NONE;
+	}
+
 	/**
 	 * Gets the datatype for this literal.
 	 * <p>

core/model-api/src/main/java/org/eclipse/rdf4j/model/ValueFactory.java

@@ -86,6 +86,18 @@ public interface ValueFactory {
 	 */
 	Literal createLiteral(String label, String language);
 
+	/**
+	 * Creates a new literal with the supplied label and language attribute. The return value of
+	 * {@link Literal#getDatatype()} for the returned object must be
+	 * <a href="http://www.w3.org/1999/02/22-rdf-syntax-ns#langString">{@code rdf:langString}</a>.
+	 *
+	 * @param label         The literal's label, must not be <var>null</var>.
+	 * @param language      The literal's language attribute, must not be <var>null</var>.
+	 * @param baseDirection The literal's base direction, either "", "--ltr", or "--rtl".
+	 * @return A literal for the specified value and language attribute.
+	 */
+	Literal createLiteral(String label, String language, Literal.BaseDirection baseDirection);
+
 	/**
 	 * Creates a new literal with the supplied label and datatype.
 	 *

core/model-api/src/main/java/org/eclipse/rdf4j/model/base/AbstractLiteral.java

@@ -77,11 +77,12 @@ public abstract class AbstractLiteral implements Literal {
 	private static final long serialVersionUID = -1286527360744086451L;
 
 	static boolean reserved(IRI datatype) {
-		return CoreDatatype.RDF.LANGSTRING.getIri().equals(datatype);
+		return CoreDatatype.RDF.LANGSTRING.getIri().equals(datatype)
+				|| CoreDatatype.RDF.DIRLANGSTRING.getIri().equals(datatype);
 	}
 
 	static boolean reserved(CoreDatatype datatype) {
-		return CoreDatatype.RDF.LANGSTRING == datatype;
+		return CoreDatatype.RDF.LANGSTRING == datatype || CoreDatatype.RDF.DIRLANGSTRING == datatype;
 	}
 
 	/**
@@ -186,7 +187,7 @@ public String toString() {
 
 		return getLanguage()
 
-				.map(language -> label + '@' + language)
+				.map(language -> label + '@' + language + getBaseDirection())
 
 				.orElseGet(() -> CoreDatatype.XSD.STRING == getCoreDatatype() ? label
 						: label + "^^<" + getDatatype().stringValue() + ">");
@@ -268,10 +269,16 @@ static class TaggedLiteral extends AbstractLiteral {
 
 		private final String label;
 		private final String language;
+		private final BaseDirection baseDirection;
 
 		TaggedLiteral(String label, String language) {
+			this(label, language, null);
+		}
+
+		TaggedLiteral(String label, String language, BaseDirection baseDirection) {
 			this.label = label;
 			this.language = language;
+			this.baseDirection = baseDirection;
 		}
 
 		@Override
@@ -284,14 +291,20 @@ public Optional<String> getLanguage() {
 			return Optional.of(language);
 		}
 
+		@Override
+		public BaseDirection getBaseDirection() {
+			return baseDirection;
+		}
+
 		@Override
 		public IRI getDatatype() {
-			return CoreDatatype.RDF.LANGSTRING.getIri();
+			return baseDirection == BaseDirection.NONE ? CoreDatatype.RDF.LANGSTRING.getIri()
+					: CoreDatatype.RDF.DIRLANGSTRING.getIri();
 		}
 
 		@Override
 		public CoreDatatype.RDF getCoreDatatype() {
-			return CoreDatatype.RDF.LANGSTRING;
+			return baseDirection == BaseDirection.NONE ? CoreDatatype.RDF.LANGSTRING : CoreDatatype.RDF.DIRLANGSTRING;
 		}
 	}
 

core/model-api/src/main/java/org/eclipse/rdf4j/model/base/AbstractValueFactory.java

@@ -146,6 +146,11 @@ public Literal createLiteral(String label, IRI datatype, CoreDatatype coreDataty
 
 	@Override
 	public Literal createLiteral(String label, String language) {
+		return createLiteral(label, language, Literal.BaseDirection.NONE);
+	}
+
+	@Override
+	public Literal createLiteral(String label, String language, Literal.BaseDirection baseDirection) {
 
 		Objects.requireNonNull(label, "null label");
 		Objects.requireNonNull(language, "null language");
@@ -154,7 +159,7 @@ public Literal createLiteral(String label, String language) {
 			throw new IllegalArgumentException("empty language tag");
 		}
 
-		return new TaggedLiteral(label, language);
+		return new TaggedLiteral(label, language, baseDirection);
 	}
 
 	@Override

core/model-api/src/main/java/org/eclipse/rdf4j/model/base/CoreDatatype.java

@@ -283,7 +283,9 @@ public String toString() {
 	enum RDF implements CoreDatatype {
 
 		HTML(iri("HTML")),
+		JSON(iri("JSON")),
 		XMLLITERAL(iri("XMLLiteral")),
+		DIRLANGSTRING(iri("dirLangString")),
 		LANGSTRING(iri("langString"));
 
 		public static final String NAMESPACE = "http://www.w3.org/1999/02/22-rdf-syntax-ns#";