--- /dev/null
+/*******************************************************************************
+ * Copyright (c) 2010, 2012 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.collection;
+
+import org.eclipse.aether.RepositorySystemSession;
+
+/**
+ * A context used during dependency collection to exchange information within a chain of dependency graph transformers.
+ *
+ * @see DependencyGraphTransformer
+ * @noimplement This interface is not intended to be implemented by clients.
+ * @noextend This interface is not intended to be extended by clients.
+ */
+public interface DependencyGraphTransformationContext
+{
+
+ /**
+ * Gets the repository system session during which the graph transformation happens.
+ *
+ * @return The repository system session, never {@code null}.
+ */
+ RepositorySystemSession getSession();
+
+ /**
+ * Gets a keyed value from the context.
+ *
+ * @param key The key used to query the value, must not be {@code null}.
+ * @return The queried value or {@code null} if none.
+ */
+ Object get( Object key );
+
+ /**
+ * Puts a keyed value into the context.
+ *
+ * @param key The key used to store the value, must not be {@code null}.
+ * @param value The value to store, may be {@code null} to remove the mapping.
+ * @return The previous value associated with the key or {@code null} if none.
+ */
+ Object put( Object key, Object value );
+
+}