diff --git a/src/fr/inrialpes/exmo/align/impl/edoal/Aggregate.java b/src/fr/inrialpes/exmo/align/impl/edoal/Aggregate.java
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+++ b/src/fr/inrialpes/exmo/align/impl/edoal/Aggregate.java
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+/*
+ * $Id$
+ *
+ * Copyright (C) INRIA, 2015
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+package fr.inrialpes.exmo.align.impl.edoal;
+
+import java.util.List;
+import java.net.URI;
+import java.net.URISyntaxException;
+
+import org.semanticweb.owl.align.AlignmentException;
+
+import fr.inrialpes.exmo.align.parser.TypeCheckingVisitor;
+import fr.inrialpes.exmo.align.parser.TypeCheckingVisitor.TYPE;
+
+/**
+ * <p>
+ * Aggregate is the aggregation of a set of values through a particular function.
+ * </p>
+ * <p>
+ * Values of {@code args} have to be aggregated with {@code op}.
+ * </p>
+ *
+ * @version $Id$
+ */
+
+public class Aggregate implements ValueExpression {
+
+    /** Holds the operation to apply */
+    private URI operation;
+
+    /** In principle, this may be a single expression, but we can generalise */
+    private List<ValueExpression> arguments;
+
+    /**
+     * Constructs an object with the given value.
+     * 
+     * @param op
+     *            the URI of the aggregation operation to apply.
+     * @param args
+     *            its list of argumenst
+     * @throws NullPointerException
+     *             if the value is {@code null}
+     */
+    public Aggregate( final URI op, final List<ValueExpression> args ) {
+	if ( op == null) {
+	    throw new NullPointerException("The operation must not be null");
+	}
+	operation = op;
+	arguments = args;
+    }
+
+    public void accept( EDOALVisitor visitor ) throws AlignmentException {
+	visitor.visit(this);
+    }
+    public TYPE accept( TypeCheckingVisitor visitor ) throws AlignmentException {
+	return visitor.visit(this);
+    }
+
+    public URI getOperation() {
+	return operation;
+    }
+
+    public List<ValueExpression> getArguments() {
+	return arguments;
+    }
+
+    public int hashCode() {
+	return 5*operation.hashCode() + 13*arguments.hashCode();
+    }
+
+    public boolean equals( final Object o ) {
+	if ( o == this ) return true;
+	if ( !(o instanceof Aggregate) ) return false;
+	Aggregate a = (Aggregate)o;
+	return ( operation.equals(a.getOperation()) && 
+		 arguments.equals(a.getArguments()) );
+    }
+}