diff --git a/NEWS b/NEWS
index 45758ced..2d52c284 100644
--- a/NEWS
+++ b/NEWS
@@ -33,6 +33,8 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
   from CSS, but you can enable it using %CSS.AllowImportant
 ! Support for display and visibility CSS properties added, set %CSS.AllowTricky
   to true to use them.
+! HTML Purifier now has its own Exception hierarchy under HTMLPurifier_Exception.
+  Developer error (not enduser error) can cause these to be triggered.
 - Autoclose now operates iteratively, i.e. <span><span><div> now has
   both span tags closed.
 - Various HTMLPurifier_Config convenience functions now accept another parameter
diff --git a/library/HTMLPurifier.includes.php b/library/HTMLPurifier.includes.php
index c8703014..511175c9 100644
--- a/library/HTMLPurifier.includes.php
+++ b/library/HTMLPurifier.includes.php
@@ -43,6 +43,7 @@ require 'HTMLPurifier/EntityLookup.php';
 require 'HTMLPurifier/EntityParser.php';
 require 'HTMLPurifier/Error.php';
 require 'HTMLPurifier/ErrorCollector.php';
+require 'HTMLPurifier/Exception.php';
 require 'HTMLPurifier/Filter.php';
 require 'HTMLPurifier/Generator.php';
 require 'HTMLPurifier/HTMLDefinition.php';
@@ -122,6 +123,8 @@ require 'HTMLPurifier/ChildDef/Table.php';
 require 'HTMLPurifier/ConfigDef/Directive.php';
 require 'HTMLPurifier/ConfigDef/DirectiveAlias.php';
 require 'HTMLPurifier/ConfigDef/Namespace.php';
+require 'HTMLPurifier/ConfigSchema/Exception.php';
+require 'HTMLPurifier/ConfigSchema/Interchange.php';
 require 'HTMLPurifier/ConfigSchema/StringHash.php';
 require 'HTMLPurifier/ConfigSchema/StringHashAdapter.php';
 require 'HTMLPurifier/ConfigSchema/StringHashParser.php';
diff --git a/library/HTMLPurifier/ConfigSchema/Exception.php b/library/HTMLPurifier/ConfigSchema/Exception.php
new file mode 100644
index 00000000..4c51d670
--- /dev/null
+++ b/library/HTMLPurifier/ConfigSchema/Exception.php
@@ -0,0 +1,9 @@
+<?php
+
+/**
+ * Exceptions related to configuration schema
+ */
+class HTMLPurifier_ConfigSchema_Exception extends HTMLPurifier_Exception
+{
+    
+}
diff --git a/library/HTMLPurifier/ConfigSchema/Interchange.php b/library/HTMLPurifier/ConfigSchema/Interchange.php
new file mode 100644
index 00000000..a155dff4
--- /dev/null
+++ b/library/HTMLPurifier/ConfigSchema/Interchange.php
@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * Generic schema interchange format that can be converted to a runtime
+ * representation (HTMLPurifier_ConfigSchema) or HTML documentation. Members
+ * are completely validated.
+ */
+class HTMLPurifier_ConfigSchema_Interchange
+{
+    
+    /**
+     * Hash table of allowed types.
+     */
+    public $types = array(
+        'string'    => 'String',
+        'istring'   => 'Case-insensitive string',
+        'text'      => 'Text',
+        'itext'      => 'Case-insensitive text',
+        'int'       => 'Integer',
+        'float'     => 'Float',
+        'bool'      => 'Boolean',
+        'lookup'    => 'Lookup array',
+        'list'      => 'Array list',
+        'hash'      => 'Associative array',
+        'mixed'     => 'Mixed'
+    );
+    
+    /**
+     * Array of Namespace ID => array(namespace info)
+     */
+    public $namespaces;
+    
+    /**
+     * Array of Directive ID => array(directive info)
+     */
+    public $directives;
+    
+    /**
+     * 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;
+    }
+    
+    /**
+     * 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;
+    }
+    
+}
diff --git a/library/HTMLPurifier/ConfigSchema/StringHashParser.php b/library/HTMLPurifier/ConfigSchema/StringHashParser.php
index fe136fed..b490be52 100644
--- a/library/HTMLPurifier/ConfigSchema/StringHashParser.php
+++ b/library/HTMLPurifier/ConfigSchema/StringHashParser.php
@@ -32,7 +32,7 @@ class HTMLPurifier_ConfigSchema_StringHashParser
     public $default = 'ID';
     
     public function parseFile($file) {
-        if (!file_exists($file)) throw new Exception('File does not exist');
+        if (!file_exists($file)) throw new HTMLPurifier_ConfigSchema_Exception('File ' . $file . ' does not exist');
         $fh = fopen($file, 'r');
         $state   = false;
         $single  = false;
diff --git a/library/HTMLPurifier/Exception.php b/library/HTMLPurifier/Exception.php
new file mode 100644
index 00000000..d36d88e0
--- /dev/null
+++ b/library/HTMLPurifier/Exception.php
@@ -0,0 +1,11 @@
+<?php
+
+/**
+ * Global exception class for HTML Purifier; any exceptions we throw
+ * are from here.
+ */
+class HTMLPurifier_Exception extends Exception
+{
+    
+}
+
diff --git a/tests/HTMLPurifier/ConfigSchema/InterchangeTest.php b/tests/HTMLPurifier/ConfigSchema/InterchangeTest.php
new file mode 100644
index 00000000..fd0e654d
--- /dev/null
+++ b/tests/HTMLPurifier/ConfigSchema/InterchangeTest.php
@@ -0,0 +1,44 @@
+<?php
+
+class HTMLPurifier_ConfigSchema_InterchangeTest extends UnitTestCase
+{
+    
+    protected $interchange;
+    
+    public function setup() {
+        $this->interchange = new HTMLPurifier_ConfigSchema_Interchange();
+    }
+    
+    public function testAddNamespace() {
+        $this->interchange->addNamespace($v = array(
+            'ID' => 'Namespace',
+            'Foo' => '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');
+        }
+    }
+    
+    public function testAddDirective() {
+        $this->interchange->addDirective($v = array(
+            'ID' => 'Namespace.Directive',
+            'Foo' => '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');
+        }
+    }
+    
+}
diff --git a/tests/HTMLPurifier/ConfigSchema/StringHashParserTest.php b/tests/HTMLPurifier/ConfigSchema/StringHashParserTest.php
index 5e6af5d9..746cb9ba 100644
--- a/tests/HTMLPurifier/ConfigSchema/StringHashParserTest.php
+++ b/tests/HTMLPurifier/ConfigSchema/StringHashParserTest.php
@@ -52,4 +52,12 @@ class HTMLPurifier_ConfigSchema_StringHashParserTest extends UnitTestCase
         ));
     }
     
+    function testError() {
+        try {
+            $this->parser->parseFile('NoExist.txt');
+        } catch (HTMLPurifier_ConfigSchema_Exception $e) {
+            $this->assertIdentical($e->getMessage(), 'File NoExist.txt does not exist');
+        }
+    }
+    
 }
diff --git a/tests/test_files.php b/tests/test_files.php
index dcfe4352..48dcfa7b 100644
--- a/tests/test_files.php
+++ b/tests/test_files.php
@@ -65,6 +65,7 @@ $test_files[] = 'HTMLPurifier/ChildDef/RequiredTest.php';
 $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/StringHashAdapterTest.php';
 $test_files[] = 'HTMLPurifier/ConfigSchema/StringHashReverseAdapterTest.php';
 $test_files[] = 'HTMLPurifier/ConfigSchema/StringHashParserTest.php';