diff --git a/library/HTMLPurifier.includes.php b/library/HTMLPurifier.includes.php
index 511175c9..7f78c017 100644
--- a/library/HTMLPurifier.includes.php
+++ b/library/HTMLPurifier.includes.php
@@ -129,6 +129,8 @@ require 'HTMLPurifier/ConfigSchema/StringHash.php';
 require 'HTMLPurifier/ConfigSchema/StringHashAdapter.php';
 require 'HTMLPurifier/ConfigSchema/StringHashParser.php';
 require 'HTMLPurifier/ConfigSchema/StringHashReverseAdapter.php';
+require 'HTMLPurifier/ConfigSchema/Interchange/Validator.php';
+require 'HTMLPurifier/ConfigSchema/Interchange/Validator/IdExists.php';
 require 'HTMLPurifier/DefinitionCache/Decorator.php';
 require 'HTMLPurifier/DefinitionCache/Null.php';
 require 'HTMLPurifier/DefinitionCache/Serializer.php';
diff --git a/library/HTMLPurifier/ConfigSchema/Interchange.php b/library/HTMLPurifier/ConfigSchema/Interchange.php
index a155dff4..5bfe1128 100644
--- a/library/HTMLPurifier/ConfigSchema/Interchange.php
+++ b/library/HTMLPurifier/ConfigSchema/Interchange.php
@@ -11,11 +11,11 @@ class HTMLPurifier_ConfigSchema_Interchange
     /**
      * Hash table of allowed types.
      */
-    public $types = array(
+    protected $types = array(
         'string'    => 'String',
         'istring'   => 'Case-insensitive string',
         'text'      => 'Text',
-        'itext'      => 'Case-insensitive text',
+        'itext'     => 'Case-insensitive text',
         'int'       => 'Integer',
         'float'     => 'Float',
         'bool'      => 'Boolean',
@@ -28,18 +28,34 @@ class HTMLPurifier_ConfigSchema_Interchange
     /**
      * Array of Namespace ID => array(namespace info)
      */
-    public $namespaces;
+    protected $namespaces;
     
     /**
      * Array of Directive ID => array(directive info)
      */
-    public $directives;
+    protected $directives;
+    
+    /** Get all namespaces */
+    public function getNamespaces() {return $this->namespaces;}
+    /** Get a namespace */
+    public function getNamespace($id) {return $this->namespaces[$id];}
+    /** Check if a namespace exists */
+    public function namespaceExists($id) {return isset($this->namespaces[$id]);}
+    
+    /** Get all directives */
+    public function getDirectives() {return $this->directives;}
+    /** Get a directive */
+    public function getDirective($id) {return $this->directives[$id];}
+    /** Check if a directive exists */
+    public function directiveExists($id) {return isset($this->directives[$id]);}
+    
+    /** Get all types */
+    public function getTypes() {return $this->types;}
     
     /**
      * Adds a namespace array to $namespaces
      */
     public function addNamespace($arr) {
-        if (!isset($arr['ID'])) throw new HTMLPurifier_ConfigSchema_Exception('Namespace must have ID');
         $this->namespaces[$arr['ID']] = $arr;
     }
     
@@ -47,8 +63,17 @@ class HTMLPurifier_ConfigSchema_Interchange
      * Adds a directive array to $directives
      */
     public function addDirective($arr) {
-        if (!isset($arr['ID'])) throw new HTMLPurifier_ConfigSchema_Exception('Directive must have ID');
         $this->directives[$arr['ID']] = $arr;
     }
     
+    /**
+     * Retrieves a version of this object wrapped in the validator adapter
+     * to be used for data-input.
+     */
+    public function getValidatorAdapter() {
+        return
+            new HTMLPurifier_ConfigSchema_Interchange_Validator_IdExists(
+            $this);
+    }
+    
 }
diff --git a/library/HTMLPurifier/ConfigSchema/Interchange/Validator.php b/library/HTMLPurifier/ConfigSchema/Interchange/Validator.php
new file mode 100644
index 00000000..fae8557d
--- /dev/null
+++ b/library/HTMLPurifier/ConfigSchema/Interchange/Validator.php
@@ -0,0 +1,43 @@
+<?php
+
+/**
+ * Base decorator class for HTMLPurifier_ConfigSchema_Interchange
+ */
+class HTMLPurifier_ConfigSchema_Interchange_Validator extends HTMLPurifier_ConfigSchema_Interchange
+{
+    /**
+     * Interchange object this schema is wrapping.
+     */
+    protected $interchange;
+    
+    /** @param Object to decorate */
+    public function __construct($i = null) {
+        $this->decorate($i);
+    }
+    
+    /** Wrap this decorator around an object. */
+    public function decorate($i) {
+        $this->interchange =  $i;
+    }
+    
+    public function getNamespaces() {
+        return $this->interchange->getNamespaces();
+    }
+    
+    public function getDirectives() {
+        return $this->interchange->getDirectives();
+    }
+    
+    public function getTypes() {
+        return $this->interchange->getTypes();
+    }
+    
+    public function addNamespace($arr) {
+        $this->interchange->addNamespace($arr);
+    }
+    
+    public function addDirective($arr) {
+        $this->interchange->addNamespace($arr);
+    }
+    
+}
diff --git a/library/HTMLPurifier/ConfigSchema/Interchange/Validator/IdExists.php b/library/HTMLPurifier/ConfigSchema/Interchange/Validator/IdExists.php
new file mode 100644
index 00000000..23153242
--- /dev/null
+++ b/library/HTMLPurifier/ConfigSchema/Interchange/Validator/IdExists.php
@@ -0,0 +1,20 @@
+<?php
+
+class HTMLPurifier_ConfigSchema_Interchange_Validator_IdExists extends HTMLPurifier_ConfigSchema_Interchange_Validator
+{
+    
+    public function addNamespace($arr) {
+        if (!isset($arr['ID'])) {
+            throw new HTMLPurifier_ConfigSchema_Exception('Namespace must have ID');
+        }
+        parent::addNamespace($arr);
+    }
+    
+    public function addDirective($arr) {
+        if (!isset($arr['ID'])) {
+            throw new HTMLPurifier_ConfigSchema_Exception('Directive must have ID');
+        }
+        parent::addDirective($arr);
+    }
+    
+}
diff --git a/tests/HTMLPurifier/ConfigSchema/Interchange/Validator/IdExistsTest.php b/tests/HTMLPurifier/ConfigSchema/Interchange/Validator/IdExistsTest.php
new file mode 100644
index 00000000..ad506ce1
--- /dev/null
+++ b/tests/HTMLPurifier/ConfigSchema/Interchange/Validator/IdExistsTest.php
@@ -0,0 +1,23 @@
+<?php
+
+class HTMLPurifier_ConfigSchema_Interchange_Validator_IdExistsTest extends HTMLPurifier_ConfigSchema_Interchange_ValidatorHarness
+{
+    
+    public function setup() {
+        parent::setup();
+        $this->validator = new HTMLPurifier_ConfigSchema_Interchange_Validator_IdExists($this->mock);
+    }
+    
+    public function testNamespace() {
+        $this->mock->expectNever('addNamespace');
+        $this->expectSchemaException('Namespace must have ID');
+        $this->validator->addNamespace();
+    }
+    
+    public function testDirective() {
+        $this->mock->expectNever('addDirective');
+        $this->expectSchemaException('Directive must have ID');
+        $this->validator->addDirective();
+    }
+    
+}
diff --git a/tests/HTMLPurifier/ConfigSchema/Interchange/ValidatorHarness.php b/tests/HTMLPurifier/ConfigSchema/Interchange/ValidatorHarness.php
new file mode 100644
index 00000000..204a8c0a
--- /dev/null
+++ b/tests/HTMLPurifier/ConfigSchema/Interchange/ValidatorHarness.php
@@ -0,0 +1,18 @@
+<?php
+
+class HTMLPurifier_ConfigSchema_Interchange_ValidatorHarness extends UnitTestCase
+{
+    
+    protected $validator;
+    protected $mock;
+    
+    public function setup() {
+        generate_mock_once('HTMLPurifier_ConfigSchema_Interchange');
+        $this->mock = new HTMLPurifier_ConfigSchema_InterchangeMock();
+    }
+    
+    protected function expectSchemaException($msg) {
+        $this->expectException(new HTMLPurifier_ConfigSchema_Exception($msg));
+    }
+    
+}
diff --git a/tests/HTMLPurifier/ConfigSchema/InterchangeTest.php b/tests/HTMLPurifier/ConfigSchema/InterchangeTest.php
index fd0e654d..d8c53e4b 100644
--- a/tests/HTMLPurifier/ConfigSchema/InterchangeTest.php
+++ b/tests/HTMLPurifier/ConfigSchema/InterchangeTest.php
@@ -12,33 +12,17 @@ class HTMLPurifier_ConfigSchema_InterchangeTest extends UnitTestCase
     public function testAddNamespace() {
         $this->interchange->addNamespace($v = array(
             'ID' => 'Namespace',
-            'Foo' => 'Bar',
+            'DESCRIPTION' => 'Bar',
         ));
-        $this->assertIdentical($v, $this->interchange->namespaces['Namespace']);
-    }
-    
-    public function testAddNamespaceError() {
-        try {
-            $this->interchange->addNamespace(array());
-        } catch (HTMLPurifier_ConfigSchema_Exception $e) {
-            $this->assertIdentical($e->getMessage(), 'Namespace must have ID');
-        }
+        $this->assertIdentical($v, $this->interchange->getNamespace('Namespace'));
     }
     
     public function testAddDirective() {
         $this->interchange->addDirective($v = array(
             'ID' => 'Namespace.Directive',
-            'Foo' => 'Bar',
+            'DESCRIPTION' => 'Bar',
         ));
-        $this->assertIdentical($v, $this->interchange->directives['Namespace.Directive']);
-    }
-    
-    public function testAddDirectiveError() {
-        try {
-            $this->interchange->addDirective(array());
-        } catch (HTMLPurifier_ConfigSchema_Exception $e) {
-            $this->assertIdentical($e->getMessage(), 'Directive must have ID');
-        }
+        $this->assertIdentical($v, $this->interchange->getDirective('Namespace.Directive'));
     }
     
 }
diff --git a/tests/test_files.php b/tests/test_files.php
index 48dcfa7b..1c818b31 100644
--- a/tests/test_files.php
+++ b/tests/test_files.php
@@ -66,6 +66,7 @@ $test_files[] = 'HTMLPurifier/ChildDef/StrictBlockquoteTest.php';
 $test_files[] = 'HTMLPurifier/ChildDef/TableTest.php';
 $test_files[] = 'HTMLPurifier/ConfigSchemaTest.php';
 $test_files[] = 'HTMLPurifier/ConfigSchema/InterchangeTest.php';
+$test_files[] = 'HTMLPurifier/ConfigSchema/Interchange/Validator/IdExistsTest.php';
 $test_files[] = 'HTMLPurifier/ConfigSchema/StringHashAdapterTest.php';
 $test_files[] = 'HTMLPurifier/ConfigSchema/StringHashReverseAdapterTest.php';
 $test_files[] = 'HTMLPurifier/ConfigSchema/StringHashParserTest.php';