GH-4230: Add GeoSPARQL 1.1 geometryN function

jena-geosparql/src/main/java/org/apache/jena/geosparql/geof/topological/filter_functions/geometry_property/GeometryNFF.java

@@ -0,0 +1,51 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ *   SPDX-License-Identifier: Apache-2.0
+ */
+package org.apache.jena.geosparql.geof.topological.filter_functions.geometry_property;
+
+import org.apache.jena.datatypes.DatatypeFormatException;
+import org.apache.jena.geosparql.implementation.GeometryWrapper;
+import org.apache.jena.sparql.expr.ExprEvalException;
+import org.apache.jena.sparql.expr.ExprEvalTypeException;
+import org.apache.jena.sparql.expr.NodeValue;
+import org.apache.jena.sparql.function.FunctionBase2;
+
+/** Implements geof:geometryN. */
+public class GeometryNFF extends FunctionBase2 {
+
+    @Override
+    public NodeValue exec(NodeValue value, NodeValue index) {
+        try {
+            GeometryWrapper geometry = GeometryWrapper.extract(value);
+            return geometry.getGeometryN(memberIndex(index)).asNodeValue();
+        } catch (DatatypeFormatException ex) {
+            throw new ExprEvalException(ex.getMessage(), ex);
+        } catch (IllegalArgumentException | ArithmeticException ex) {
+            throw new ExprEvalException(ex.getMessage(), ex);
+        }
+    }
+
+    private static int memberIndex(NodeValue index) {
+        if (!index.isInteger()) {
+            throw new ExprEvalTypeException("Geometry member index must be an xsd:integer: " + index);
+        }
+        return index.getInteger().intValueExact();
+    }
+}

jena-geosparql/src/main/java/org/apache/jena/geosparql/implementation/DimensionInfo.java

@@ -28,6 +28,11 @@
 
 import org.apache.jena.geosparql.implementation.jts.CoordinateSequenceDimensions;
 import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.CoordinateSequence;
+import org.locationtech.jts.geom.GeometryCollection;
+import org.locationtech.jts.geom.LineString;
+import org.locationtech.jts.geom.Point;
+import org.locationtech.jts.geom.Polygon;
 import org.locationtech.jts.geom.CoordinateXY;
 import org.locationtech.jts.geom.Geometry;
 
@@ -90,6 +95,31 @@ public static int findCoordinateDimension(CoordinateSequenceDimensions dims) {
         }
     }
 
+    /**
+     * Finds dimension metadata from coordinate sequences, preserving Z/M layouts
+     * even when the sequence is empty. Collections use their first member's
+     * layout, layout retained on an empty aggregate, or the fallback when they
+     * have no members.
+     */
+    public static DimensionInfo find(Geometry geometry, CoordinateSequenceDimensions fallback) {
+        CoordinateSequence sequence = null;
+        if (geometry instanceof Point point) {
+            sequence = point.getCoordinateSequence();
+        } else if (geometry instanceof LineString line) {
+            sequence = line.getCoordinateSequence();
+        } else if (geometry instanceof Polygon polygon) {
+            sequence = polygon.getExteriorRing().getCoordinateSequence();
+        } else if (geometry instanceof GeometryCollection collection && collection.getNumGeometries() > 0) {
+            fallback = find(collection.getGeometryN(0), fallback).getDimensions();
+        } else if (geometry.getUserData() instanceof CoordinateSequenceDimensions retained) {
+            // WKTReader stores parsed layout here; empty aggregates have no sequence.
+            fallback = retained;
+        }
+        CoordinateSequenceDimensions dimensions = sequence == null ? fallback
+            : findCoordinateSequenceDimensions(sequence.getDimension(), sequence.getDimension() - sequence.getMeasures());
+        return new DimensionInfo(dimensions, geometry.getDimension());
+    }
+
     public static DimensionInfo find(Coordinate coordinate, Geometry geometry) {
         // Empty geometries have no coordinate; use the existing XY default.
         CoordinateSequenceDimensions coordDims = CoordinateSequenceDimensions.find(

jena-geosparql/src/main/java/org/apache/jena/geosparql/implementation/GeometryWrapper.java

@@ -49,6 +49,7 @@
 import org.locationtech.jts.geom.CoordinateXY;
 import org.locationtech.jts.geom.Envelope;
 import org.locationtech.jts.geom.Geometry;
+import org.locationtech.jts.geom.GeometryCollection;
 import org.locationtech.jts.geom.GeometryFactory;
 import org.locationtech.jts.geom.IntersectionMatrix;
 import org.locationtech.jts.geom.Point;
@@ -475,6 +476,26 @@ public double getMaxZ() {
         return GeometryCoordinateExtrema.maxZ(this);
     }
 
+    /**
+     * Selects a direct geometry member using a one-based index, without flattening
+     * nested collections. Index 1 selects an atomic geometry itself, including
+     * an empty atomic geometry. Retains the source datatype and SRS and uses the
+     * selected member's coordinate layout.
+     *
+     * @throws IllegalArgumentException if the index is outside the member range.
+     */
+    public GeometryWrapper getGeometryN(int index) {
+        if (index < 1 || index > parsingGeometry.getNumGeometries()) {
+            throw new IllegalArgumentException("Geometry member index is out of range: " + index);
+        }
+        if (!(parsingGeometry instanceof GeometryCollection)) {
+            return this;
+        }
+        Geometry member = parsingGeometry.getGeometryN(index - 1);
+        DimensionInfo dimensions = DimensionInfo.find(member, dimensionInfo.getDimensions());
+        return new GeometryWrapper(member, getSrsURI(), geometryDatatypeURI, dimensions);
+    }
+
     /**
      *
      * @return GeometryDatatype of the literal.

jena-geosparql/src/main/java/org/apache/jena/geosparql/implementation/function_registration/GeometryProperty.java

@@ -28,6 +28,7 @@
 import org.apache.jena.geosparql.geo.topological.property_functions.geometry_property.SpatialDimensionPF;
 import org.apache.jena.geosparql.geof.topological.filter_functions.geometry_property.CoordinateDimensionFF;
 import org.apache.jena.geosparql.geof.topological.filter_functions.geometry_property.DimensionFF;
+import org.apache.jena.geosparql.geof.topological.filter_functions.geometry_property.GeometryNFF;
 import org.apache.jena.geosparql.geof.topological.filter_functions.geometry_property.Is3DFF;
 import org.apache.jena.geosparql.geof.topological.filter_functions.geometry_property.IsEmptyFF;
 import org.apache.jena.geosparql.geof.topological.filter_functions.geometry_property.IsMeasuredFF;
@@ -70,7 +71,7 @@ public static void loadPropertyFunctions(PropertyFunctionRegistry registry) {
     /**
      * Registers {@code geof:} expression functions with the supplied registry.
      *
-     * @param registry - the FunctionRegistry to be used
+     * @param registry the FunctionRegistry to use
      */
     public static void loadFilterFunctions(FunctionRegistry registry) {
 
@@ -83,13 +84,14 @@ public static void loadFilterFunctions(FunctionRegistry registry) {
         registry.put(Geof.IS_SIMPLE, IsSimpleFF.class);
         registry.put(Geof.IS_EMPTY, IsEmptyFF.class);
         registry.put(Geof.IS_VALID, IsValidFF.class);
-
         registry.put(Geof.MIN_X, MinXFF.class);
         registry.put(Geof.MIN_Y, MinYFF.class);
         registry.put(Geof.MIN_Z, MinZFF.class);
         registry.put(Geof.MAX_X, MaxXFF.class);
         registry.put(Geof.MAX_Y, MaxYFF.class);
         registry.put(Geof.MAX_Z, MaxZFF.class);
+
+        registry.put(Geof.GEOMETRY_N, GeometryNFF.class);
     }
 
 }

jena-geosparql/src/main/java/org/apache/jena/geosparql/implementation/parsers/gml/GMLReader.java

@@ -481,7 +481,7 @@ private static Polygon buildPolygon(Element gmlElement, CoordinateSequenceDimens
             Element exteriorLinearRingElement = exteriorElement.getChild("LinearRing", GML_NAMESPACE);
             exteriorLinearRing = buildLinearRing(exteriorLinearRingElement, dims);
         } else {
-            exteriorLinearRing = GEOMETRY_FACTORY.createLinearRing();
+            exteriorLinearRing = GEOMETRY_FACTORY.createLinearRing(new CustomCoordinateSequence(dims));
         }
         //Interior shell - [0..*]
         List<Element> interiorElements = gmlElement.getChildren("interior", GML_NAMESPACE);
@@ -536,7 +536,7 @@ private static Polygon buildSurface(Element gmlElement, CoordinateSequenceDimens
                 Geometry exteriorGeom = buildSurfacePatch(exteriorElement, dims, srsInfo);
                 exteriorLinearRing = GEOMETRY_FACTORY.createLinearRing(exteriorGeom.getCoordinates());
             } else {
-                exteriorLinearRing = GEOMETRY_FACTORY.createLinearRing();
+                exteriorLinearRing = GEOMETRY_FACTORY.createLinearRing(new CustomCoordinateSequence(dims));
             }
 
             //Interior shell - [0..*]
@@ -559,6 +559,12 @@ private static Polygon buildSurface(Element gmlElement, CoordinateSequenceDimens
             polys.add(polygon);
         }
 
+        // The union of empty patches is a GeometryCollection in JTS.
+        // Return an empty patch directly so its coordinate layout is retained.
+        if (polys.stream().allMatch(Polygon::isEmpty)) {
+            return polys.get(0);
+        }
+
         //Unionise all the polygons on the surface together.
         Geometry unionGeom = CascadedPolygonUnion.union(polys);
         Polygon unionPolygon;

jena-geosparql/src/main/java/org/apache/jena/geosparql/implementation/parsers/gml/GMLWriter.java

@@ -182,7 +182,7 @@ private static Element buildMultiPoint(final MultiPoint multiPoint, final String
         Element gmlRoot = new Element(multiPoint.getGeometryType(), GML_NAMESPACE);
         gmlRoot.setAttribute("srsName", srsName);
 
-        if (!multiPoint.isEmpty()) {
+        if (multiPoint.getNumGeometries() > 0) {
 
             int geomCount = multiPoint.getNumGeometries();
             for (int i = 0; i < geomCount; i++) {
@@ -206,7 +206,7 @@ private static Element buildMultiLineString(final MultiLineString multiLineStrin
         Element gmlRoot = new Element("MultiCurve", GML_NAMESPACE);
         gmlRoot.setAttribute("srsName", srsName);
 
-        if (!multiLineString.isEmpty()) {
+        if (multiLineString.getNumGeometries() > 0) {
 
             int geomCount = multiLineString.getNumGeometries();
             for (int i = 0; i < geomCount; i++) {
@@ -231,7 +231,7 @@ private static Element buildMultiPolygon(final MultiPolygon multiPolygon, final
         Element gmlRoot = new Element("MultiSurface", GML_NAMESPACE);
         gmlRoot.setAttribute("srsName", srsName);
 
-        if (!multiPolygon.isEmpty()) {
+        if (multiPolygon.getNumGeometries() > 0) {
 
             int geomCount = multiPolygon.getNumGeometries();
             for (int i = 0; i < geomCount; i++) {
@@ -256,7 +256,7 @@ private static Element buildMultiGeometry(final GeometryCollection geometryColle
         Element gmlRoot = new Element("MultiGeometry", GML_NAMESPACE);
         gmlRoot.setAttribute("srsName", srsName);
 
-        if (!geometryCollection.isEmpty()) {
+        if (geometryCollection.getNumGeometries() > 0) {
 
             int geomCount = geometryCollection.getNumGeometries();
             for (int i = 0; i < geomCount; i++) {