#13 add preferred language setting to limit the literals being returned

README.md

@@ -138,3 +138,16 @@ spider.`name_literal@ru`.println('Name literal of Spiderman in Russian: ');
 * `value`: the raw value of the literal (usually a String, but it can be different for typed literals - see [Apache Jena typed literals](https://jena.apache.org/documentation/notes/typed-literals.html)).
 * `language`: the language tag for the literal (if any).
 * `datatypeURI`: the datatype URI for the literal.
+
+### Limiting returned literals to preferred languages
+
+The "Language tag preference" section of the RDF model configuration dialog allows for specifying a comma-separated list of [BCP 47](https://www.ietf.org/rfc/bcp/bcp47.txt) language tags.
+If these preferences are set, `x.property` will filter literals, by only returning the values for the first tag with matches, or falling back to the untagged values if no matches are found for any of the mentioned tags.
+
+For instance, if we set the language preferences to `en-gb,en`, filtering `x.property` will work as follows:
+
+* If any `en-gb` literals exist, return only those.
+* If any `en` literals exist, return only those.
+* Otherwise, return the untagged literals (if any).
+
+Language preferences do not apply if an explicit language tag is used: `x.property@en` will always get the `en`-tagged literals, and `x.property@` will always get the untagged literals.

bundles/org.eclipse.epsilon.emc.rdf.dt/.settings/org.eclipse.core.resources.prefs

@@ -0,0 +1,2 @@
+eclipse.preferences.version=1
+encoding/<project>=UTF-8

bundles/org.eclipse.epsilon.emc.rdf.dt/src/org/eclipse/epsilon/emc/rdf/dt/RDFModelConfigurationDialog.java

@@ -15,8 +15,10 @@
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 import org.eclipse.core.resources.IFile;
@@ -33,13 +35,17 @@
 import org.eclipse.jface.viewers.TableViewerColumn;
 import org.eclipse.jface.viewers.TextCellEditor;
 import org.eclipse.swt.SWT;
+import org.eclipse.swt.events.ModifyEvent;
+import org.eclipse.swt.events.ModifyListener;
 import org.eclipse.swt.events.SelectionAdapter;
 import org.eclipse.swt.events.SelectionEvent;
 import org.eclipse.swt.layout.FillLayout;
 import org.eclipse.swt.layout.GridData;
 import org.eclipse.swt.widgets.Button;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.FileDialog;
+import org.eclipse.swt.widgets.Label;
+import org.eclipse.swt.widgets.Text;
 
 public class RDFModelConfigurationDialog extends AbstractModelConfigurationDialog {
 
@@ -74,7 +80,7 @@ protected Object getValue(Object element) {
 		protected void setValue(Object element, Object value) {
 			((NamespaceMappingTableEntry)element).prefix = String.valueOf(value);
 			viewer.update(element, null);
-			validateURLs();
+			validateForm();
 		}
 	}
 
@@ -107,7 +113,7 @@ protected Object getValue(Object element) {
 		protected void setValue(Object element, Object value) {
 			((NamespaceMappingTableEntry)element).url = String.valueOf(value);
 			viewer.update(element, null);
-			validateURLs();
+			validateForm();
 		}
 	}
 
@@ -140,7 +146,7 @@ protected Object getValue(Object element) {
 		protected void setValue(Object element, Object value) {
 			((URLTableEntry)element).url = String.valueOf(value);
 			viewer.update(element, null);
-			validateURLs();
+			validateForm();
 		}
 	}
 
@@ -177,6 +183,7 @@ protected void createGroups(Composite control) {
 		createNameAliasGroup(control);
 		createRDFUrlsGroup(control);
 		createNamespaceMappingGroup(control);
+		createLanguagePreferenceGroup(control);
 	}
 
 	private Composite createNamespaceMappingGroup(Composite parent) {
@@ -346,6 +353,7 @@ public void widgetSelected(SelectionEvent e) {
 						urls.remove(it.next());
 					}
 					urlList.refresh();
+					validateForm();
 				}
 			}
 		});
@@ -357,6 +365,7 @@ public void widgetSelected(SelectionEvent e) {
 			public void widgetSelected(SelectionEvent e) {
 				urls.clear();
 				urlList.refresh();
+				validateForm();
 			}
 		});
 
@@ -365,6 +374,30 @@ public void widgetSelected(SelectionEvent e) {
 		return groupContent;
 	}
 
+
+	protected Label languagePreferenceLabel;
+	protected Text languagePreferenceText;
+
+	private Composite createLanguagePreferenceGroup(Composite parent) {
+		final Composite groupContent = DialogUtil.createGroupContainer(parent, "Language tag preference", 1);
+
+		languagePreferenceLabel = new Label(groupContent, SWT.NONE);
+		languagePreferenceLabel.setText("Comma-separated preferred language tags, in descending priority:");
+
+		languagePreferenceText = new Text(groupContent, SWT.BORDER);
+		languagePreferenceText.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));	
+		languagePreferenceText.addModifyListener(new ModifyListener() {
+			@Override
+			public void modifyText(ModifyEvent event) {
+				validateForm();
+			}
+		});
+
+		groupContent.layout();
+		groupContent.pack();
+		return groupContent;
+	}
+
 	@Override
 	protected void loadProperties(){
 		super.loadProperties();
@@ -389,12 +422,14 @@ protected void loadProperties(){
 				}
 			}
 		}
+
+		languagePreferenceText.setText(properties.getProperty(RDFModel.PROPERTY_LANGUAGE_PREFERENCE));
 
 		this.urlList.refresh();
 		this.nsMappingTable.refresh();
-		validateURLs();
+		validateForm();
 	}
-
+	 
 	@Override
 	protected void storeProperties(){
 		super.storeProperties();
@@ -408,9 +443,27 @@ protected void storeProperties(){
 			String.join(",", nsMappingEntries.stream()
 				.map(e -> e.prefix + "=" + e.url)
 				.collect(Collectors.toList())));
+
+		properties.put(RDFModel.PROPERTY_LANGUAGE_PREFERENCE,
+				languagePreferenceText.getText().replaceAll("\\s", ""));
 	}
 
-	protected void validateURLs() {
+	protected void validateForm() {
+		String text = languagePreferenceText.getText().strip();
+		if (text.length() > 0) {
+			Set<String> invalidTags = new HashSet<>();
+			for (String tag : text.split(",")) {
+				if (!RDFModel.isValidLanguageTag(tag)) {
+					invalidTags.add(tag);
+				}
+			}
+			if (!invalidTags.isEmpty()) {
+				setErrorMessage(String.format(
+					"Invalid tags: %s", String.join(" ", invalidTags)));
+				return;
+			}
+		}
+
 		for (URLTableEntry entry : this.urls) {
 			String errorMessage = validateURL(entry.url);
 			if (errorMessage != null) {

bundles/org.eclipse.epsilon.emc.rdf/.settings/org.eclipse.core.resources.prefs

@@ -0,0 +1,2 @@
+eclipse.preferences.version=1
+encoding/<project>=UTF-8

bundles/org.eclipse.epsilon.emc.rdf/src/org/eclipse/epsilon/emc/rdf/RDFModel.java

@@ -17,6 +17,7 @@
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Map.Entry;
 
@@ -38,6 +39,8 @@
 
 public class RDFModel extends CachedModel<RDFModelElement> {
 
+	public static final String PROPERTY_LANGUAGE_PREFERENCE = "languagePreference";
+
 	public static final String PROPERTY_URIS = "uris";
 
 	/**
@@ -50,6 +53,7 @@ public class RDFModel extends CachedModel<RDFModelElement> {
 	 */
 	public static final String PROPERTY_PREFIXES = "prefixes";
 
+	protected final List<String> languagePreference = new ArrayList<>();
 	protected final Map<String, String> customPrefixesMap = new HashMap<>();
 	protected final List<String> uris = new ArrayList<>();
 	protected Model model;
@@ -136,13 +140,16 @@ public void load(StringProperties properties, IRelativePathResolver resolver) th
 		 * EMC drivers (e.g. the EmfModel class).
 		 */
 		this.uris.clear();
-		for (String uri : properties.getProperty(PROPERTY_URIS).split(",")) {
-			this.uris.add(uri.strip());
+		String sUris = properties.getProperty(PROPERTY_URIS, "").strip();
+		if (!sUris.isEmpty()) {
+			for (String uri : sUris.split(",")) {
+				this.uris.add(uri.strip());
+			}
 		}
 
 		this.customPrefixesMap.clear();
 		String sPrefixes = properties.getProperty(PROPERTY_PREFIXES, "").strip();
-		if (sPrefixes.length() > 0) {
+		if (!sPrefixes.isEmpty()) {
 			for (String sItem : sPrefixes.split(",")) {
 				int idxEquals = sItem.indexOf('=');
 				if (idxEquals <= 0 || idxEquals == sItem.length() - 1) {
@@ -154,6 +161,22 @@ public void load(StringProperties properties, IRelativePathResolver resolver) th
 				customPrefixesMap.put(sPrefix, sURI);
 			}
 		}
+
+		this.languagePreference.clear();
+		String sLanguagePreference = properties.getProperty(PROPERTY_LANGUAGE_PREFERENCE, "").strip();
+		if (!sLanguagePreference.isEmpty()) {
+			for (String tag : sLanguagePreference.split(",")) {
+				tag = tag.strip();
+				if (isValidLanguageTag(tag)) {
+					this.languagePreference.add(tag);
+				} else {
+					throw new EolModelLoadingException(
+						new IllegalArgumentException(
+							String.format("'%s' is not a valid BCP 47 tag", tag)
+						), this);
+				}
+			}
+		}
 
 		load();
 	}
@@ -300,6 +323,10 @@ public void setUri(String uri) {
 	public Map<String, String> getCustomPrefixesMap() {
 		return this.customPrefixesMap;
 	}
+
+	public List<String> getLanguagePreference() {
+		return languagePreference;
+	}
 
 	/**
 	 * <p>
@@ -338,4 +365,10 @@ public String getPrefix(String namespaceURI) {
 		}
 		return model.getNsURIPrefix(namespaceURI);
 	}
+
+	// Using Java's Locale class to check that tags conform to bcp47 structure
+	public static boolean isValidLanguageTag (String bcp47tag) {
+		boolean isValidBCP47 = !("und".equals(Locale.forLanguageTag(bcp47tag).toLanguageTag()));
+		return isValidBCP47;
+	}
 }

bundles/org.eclipse.epsilon.emc.rdf/src/org/eclipse/epsilon/emc/rdf/RDFQualifiedName.java

@@ -73,6 +73,10 @@ public static RDFQualifiedName from(String prefix, String nsURI, String localNam
 	public RDFQualifiedName withLocalName(String newLocalName) {
 		return new RDFQualifiedName(prefix, namespaceURI, newLocalName, languageTag);
 	}
+
+	public RDFQualifiedName withLanguageTag(String newLanguageTag) {
+		return new RDFQualifiedName(prefix, namespaceURI, localName, newLanguageTag);
+	}
 
 	@Override
 	public String toString() {