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diff --git a/org.argeo.slc.repo/src/org/eclipse/aether/SessionData.java b/org.argeo.slc.repo/src/org/eclipse/aether/SessionData.java
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+/*******************************************************************************
+ * Copyright (c) 2010, 2014 Sonatype, Inc.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Sonatype, Inc. - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.aether;
+
+/**
+ * A container for data that is specific to a repository system session. Both components within the repository system
+ * and clients of the system may use this storage to associate arbitrary data with a session.
+ * <p>
+ * Unlike a cache, this session data is not subject to purging. For this same reason, session data should also not be
+ * abused as a cache (i.e. for storing values that can be re-calculated) to avoid memory exhaustion.
+ * <p>
+ * <strong>Note:</strong> Actual implementations must be thread-safe.
+ * 
+ * @see RepositorySystemSession#getData()
+ * @noimplement This interface is not intended to be implemented by clients.
+ * @noextend This interface is not intended to be extended by clients.
+ */
+public interface SessionData
+{
+
+    /**
+     * Associates the specified session data with the given key.
+     * 
+     * @param key The key under which to store the session data, must not be {@code null}.
+     * @param value The data to associate with the key, may be {@code null} to remove the mapping.
+     */
+    void set( Object key, Object value );
+
+    /**
+     * Associates the specified session data with the given key if the key is currently mapped to the given value. This
+     * method provides an atomic compare-and-update of some key's value.
+     * 
+     * @param key The key under which to store the session data, must not be {@code null}.
+     * @param oldValue The expected data currently associated with the key, may be {@code null}.
+     * @param newValue The data to associate with the key, may be {@code null} to remove the mapping.
+     * @return {@code true} if the key mapping was successfully updated from the old value to the new value,
+     *         {@code false} if the current key mapping didn't match the expected value and was not updated.
+     */
+    boolean set( Object key, Object oldValue, Object newValue );
+
+    /**
+     * Gets the session data associated with the specified key.
+     * 
+     * @param key The key for which to retrieve the session data, must not be {@code null}.
+     * @return The session data associated with the key or {@code null} if none.
+     */
+    Object get( Object key );
+
+}