--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.truffle.api.dsl/src/com/oracle/truffle/api/dsl/TypeSystem.java	Mon Jul 01 20:58:32 2013 +0200
@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2012, 2012, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.oracle.truffle.api.dsl;
+
+import java.lang.annotation.*;
+
+import com.oracle.truffle.api.nodes.*;
+
+/**
+ * <p>
+ * Each {@link Node} has one {@link TypeSystem} at its root to define the types that can be used
+ * throughout the system. Multiple {@link TypeSystem}s are allowed, but they cannot be mixed inside
+ * a single {@link Node} hierarchy. A {@link TypeSystem} defines a list of types as its child
+ * elements, in which every type precedes its super types.The latter condition ensures that the most
+ * concrete type is found first when searching the list sequentially for the type of a given generic
+ * value.
+ * </p>
+ * 
+ * <p>
+ * Each {@link #value()} is represented as a java type. A type can specify two annotations:
+ * {@link TypeCheck} and {@link TypeCast}. The {@link TypeCheck} checks whether a given generic
+ * value matches to the current type. The {@link TypeCast} casts a generic type value to the current
+ * type. If the {@link TypeCheck} and {@link TypeCast} annotations are not declared in the
+ * {@link TypeSystem} the a default implementation is provided. The default implementation of
+ * {@link TypeCheck} returns <code>true</code> only on an exact type match and {@link TypeCast} is
+ * only a cast to this type. Specified methods with {@link TypeCheck} and {@link TypeCast} may be
+ * used to extend the definition of a type in the language. In our example, the
+ * <code>isInteger</code> and <code>asInteger</code> methods are defined in a way so that they
+ * accept also {@link Integer} values, implicitly converting them to {@link Double} . This example
+ * points out how we express implicit type conversions.
+ * </p>
+ * 
+ * <p>
+ * <b>Example:</b> The {@link TypeSystem} contains the types {@link Boolean}, {@link Integer}, and
+ * {@link Double}. The type {@link Object} is always used implicitly as the generic type represent
+ * all values.
+ * 
+ * <pre>
+ * 
+ * {@literal @}TypeSystem(types = {boolean.class, int.class, double.class})
+ * public abstract class ExampleTypeSystem {
+ * 
+ *     {@literal @}TypeCheck
+ *     public boolean isInteger(Object value) {
+ *         return value instanceof Integer || value instanceof Double;
+ *     }
+ * 
+ *     {@literal @}TypeCast
+ *     public double asInteger(Object value) {
+ *         return ((Number)value).doubleValue();
+ *     }
+ * }
+ * </pre>
+ * 
+ * </p>
+ * 
+ * @see TypeCast
+ * @see TypeCheck
+ */
+@Retention(RetentionPolicy.CLASS)
+@Target({ElementType.TYPE})
+public @interface TypeSystem {
+
+    /**
+     * The list of types as child elements of the {@link TypeSystem}. Each precedes its super type.
+     */
+    Class[] value();
+
+}