diff --git a/library/HTMLPurifier/CSSDefinition.php b/library/HTMLPurifier/CSSDefinition.php
index 4db04694..e5d963f3 100644
--- a/library/HTMLPurifier/CSSDefinition.php
+++ b/library/HTMLPurifier/CSSDefinition.php
@@ -24,6 +24,8 @@ require_once 'HTMLPurifier/AttrDef/Enum.php';
 class HTMLPurifier_CSSDefinition extends HTMLPurifier_Definition
 {
     
+    var $type = 'CSS';
+    
     /**
      * Assoc array of attribute name to definition object.
      */
diff --git a/library/HTMLPurifier/Config.php b/library/HTMLPurifier/Config.php
index 38011a53..25522d58 100644
--- a/library/HTMLPurifier/Config.php
+++ b/library/HTMLPurifier/Config.php
@@ -6,6 +6,7 @@ require_once 'HTMLPurifier/ConfigSchema.php';
 require_once 'HTMLPurifier/HTMLDefinition.php';
 require_once 'HTMLPurifier/CSSDefinition.php';
 require_once 'HTMLPurifier/Doctype.php';
+require_once 'HTMLPurifier/DefinitionCache.php';
 
 /**
  * Configuration object that triggers customizable behavior.
@@ -176,11 +177,9 @@ class HTMLPurifier_Config
         // reset definitions if the directives they depend on changed
         // this is a very costly process, so it's discouraged 
         // with finalization
-        if ($namespace == 'HTML' || $namespace == 'Attr') {
+        if ($namespace == 'HTML') {
             $this->html_definition = null;
-            $this->doctype = null;
-        }
-        if ($namespace == 'CSS') {
+        } elseif ($namespace == 'CSS') {
             $this->css_definition = null;
         }
     }
@@ -192,34 +191,59 @@ class HTMLPurifier_Config
      */
     function &getHTMLDefinition($raw = false) {
         if (!$this->finalized && $this->autoFinalize) $this->finalize();
-        if (
-            empty($this->html_definition) || // hasn't ever been setup
-            ($raw && $this->html_definition->setup) // requesting new one
-        ) {
-            if (!$raw) {
-                $this->html_definition = HTMLPurifier_HTMLDefinition::getCache($this);
-                if ($this->html_definition) return $this->html_definition;
-            }
-            $this->html_definition = new HTMLPurifier_HTMLDefinition();
-            if ($raw) return $this->html_definition; // no setup!
+        $cache = HTMLPurifier_DefinitionCache::create('HTML', $this);
+        if($this->checkDefinition($this->html_definition, $cache, $raw)) {
+            return $this->html_definition;
         }
-        if (!$this->html_definition->setup) {
-            $this->html_definition->setup($this);
-            $this->html_definition->saveCache($this);
-        }
-        return $this->html_definition;
+        return $this->createDefinition(
+            $this->html_definition,
+            $cache,
+            $raw, 
+            new HTMLPurifier_HTMLDefinition()
+        );
     }
     
     /**
      * Retrieves reference to the CSS definition
      */
-    function &getCSSDefinition() {
+    function &getCSSDefinition($raw = false) {
         if (!$this->finalized && $this->autoFinalize) $this->finalize();
-        if ($this->css_definition === null) {
-            $this->css_definition = new HTMLPurifier_CSSDefinition();
-            $this->css_definition->setup($this);
+        $cache = HTMLPurifier_DefinitionCache::create('CSS', $this);
+        if($this->checkDefinition($this->css_definition, $cache, $raw)) {
+            return $this->css_definition;
         }
-        return $this->css_definition;
+        return $this->createDefinition(
+            $this->css_definition,
+            $cache,
+            $raw, 
+            new HTMLPurifier_CSSDefinition()
+        );
+    }
+    
+    /**
+     * Checks the variable and cache for an easy-access definition,
+     * sets def to variable and returns true if available
+     */
+    function checkDefinition(&$var, $cache, $raw) {
+        if ($raw) return false;
+        if (!empty($var)) {
+            if (!$var->setup) $var->setup($this);
+            return true;
+        }
+        $var = $cache->get($this);
+        return (bool) $var;
+    }
+    
+    /**
+     * Generates a new definition, possibly returning it raw, returns
+     * reference to variable.
+     */
+    function &createDefinition(&$var, $cache, $raw, $obj) {
+        $var = $obj;
+        if ($raw) return $var;
+        $var->setup($this);
+        $cache->set($var, $this);
+        return $var;
     }
     
     /**
@@ -266,6 +290,14 @@ class HTMLPurifier_Config
         return $this->finalized;
     }
     
+    /**
+     * Finalizes configuration only if auto finalize is on and not
+     * already finalized
+     */
+    function autoFinalize() {
+        if (!$this->finalized && $this->autoFinalize) $this->finalize();
+    }
+    
     /**
      * Finalizes a configuration object, prohibiting further change
      */
diff --git a/library/HTMLPurifier/Definition.php b/library/HTMLPurifier/Definition.php
index 2a430bde..f45951bb 100644
--- a/library/HTMLPurifier/Definition.php
+++ b/library/HTMLPurifier/Definition.php
@@ -12,6 +12,11 @@ class HTMLPurifier_Definition
      */
     var $setup = false;
     
+    /**
+     * What type of definition is it?
+     */
+    var $type;
+    
     /**
      * Sets up the definition object into the final form, something
      * not done by the constructor
diff --git a/library/HTMLPurifier/DefinitionCache.php b/library/HTMLPurifier/DefinitionCache.php
new file mode 100644
index 00000000..7e9942f3
--- /dev/null
+++ b/library/HTMLPurifier/DefinitionCache.php
@@ -0,0 +1,83 @@
+<?php
+
+require_once 'HTMLPurifier/DefinitionCache/Serializer.php';
+
+/**
+ * Abstract class representing Definition cache managers that implements
+ * useful common methods and is a factory.
+ * @note The configuration object is transformed into the key used by the cache
+ * @todo Implement flush()
+ * @todo Implement replace()
+ * @todo Get some sort of versioning variable so the library can easily
+ *       invalidate the cache with a new version
+ * @todo Make the test runner cache aware and allow the user to easily
+ *       flush the cache
+ * @todo Create a separate maintenance file advanced users can use to
+ *       cache their custom HTMLDefinition, which can be loaded
+ *       via a configuration directive
+ * @todo Implement memcached
+ * @todo Perform type checking on $def objects
+ */
+class HTMLPurifier_DefinitionCache
+{
+    
+    var $type;
+    
+    /**
+     * @param $name Type of definition objects this instance of the
+     *      cache will handle.
+     */
+    function HTMLPurifier_DefinitionCache($type) {
+        $this->type = $type;
+    }
+    
+    /**
+     * Generates a unique identifier for a particular configuration
+     * @param Instance of HTMLPurifier_Config
+     */
+    function generateKey($config) {
+        return md5(serialize($config->getBatch($this->type)));
+    }
+    
+    /**
+     * Factory method that creates a cache object based on configuration
+     * @param $name Name of definitions handled by cache
+     * @param $config Instance of HTMLPurifier_Config
+     */
+    function create($name, $config) {
+        // only one implementation as for right now, $config will
+        // be used to determine implementation
+        return new HTMLPurifier_DefinitionCache_Serializer($name);
+    }
+    
+    /**
+     * Adds a definition object to the cache
+     */
+    function add($def, $config) {
+        trigger_error('Cannot call abstract method', E_USER_ERROR);
+    }
+    
+    /**
+     * Unconditionally saves a definition object to the cache
+     */
+    function set($def, $config) {
+        trigger_error('Cannot call abstract method', E_USER_ERROR);
+    }
+    
+    /**
+     * Retrieves a definition object from the cache
+     */
+    function get($config) {
+        trigger_error('Cannot call abstract method', E_USER_ERROR);
+    }
+    
+    /**
+     * Removes a definition object to the cache
+     */
+    function remove($config) {
+        trigger_error('Cannot call abstract method', E_USER_ERROR);
+    }
+    
+}
+
+?>
\ No newline at end of file
diff --git a/library/HTMLPurifier/DefinitionCache/Serializer.php b/library/HTMLPurifier/DefinitionCache/Serializer.php
new file mode 100644
index 00000000..ab5398bf
--- /dev/null
+++ b/library/HTMLPurifier/DefinitionCache/Serializer.php
@@ -0,0 +1,64 @@
+<?php
+
+require_once 'HTMLPurifier/DefinitionCache.php';
+
+class HTMLPurifier_DefinitionCache_Serializer extends
+      HTMLPurifier_DefinitionCache
+{
+    
+    function add($def, $config) {
+        $file = $this->generateFilePath($config);
+        if (file_exists($file)) return false;
+        return $this->_write($file, serialize($def));
+    }
+    
+    function set($def, $config) {
+        $file = $this->generateFilePath($config);
+        return $this->_write($file, serialize($def));
+    }
+    
+    function get($config) {
+        $file = $this->generateFilePath($config);
+        if (!file_exists($file)) return false;
+        return unserialize(file_get_contents($file));
+    }
+    
+    function remove($config) {
+        $file = $this->generateFilePath($config);
+        if (!file_exists($file)) return false;
+        return unlink($file);
+    }
+    
+    /**
+     * Generates the file path to the serial file corresponding to
+     * the configuration and definition name
+     */
+    function generateFilePath($config) {
+        $key = $this->generateKey($config);
+        return dirname(__FILE__) . '/Serializer/' . $this->type . '/' . $key . '.ser';
+    }
+    
+    /**
+     * Convenience wrapper function for file_put_contents
+     * @param $file File name to write to
+     * @param $data Data to write into file
+     * @return Number of bytes written if success, or false if failure.
+     */
+    function _write($file, $data) {
+        static $file_put_contents;
+        if ($file_put_contents === null) {
+            $file_put_contents = function_exists('file_put_contents');
+        }
+        if ($file_put_contents) {
+            return file_put_contents($file, $data);
+        }
+        $fh = fopen($file, 'w');
+        if (!$fh) return false;
+        $status = fwrite($fh, $contents);
+        fclose($fh);
+        return $status;
+    }
+    
+}
+
+?>
\ No newline at end of file
diff --git a/library/HTMLPurifier/HTMLDefinition.php b/library/HTMLPurifier/HTMLDefinition.php
index 5b66a871..a3505877 100644
--- a/library/HTMLPurifier/HTMLDefinition.php
+++ b/library/HTMLPurifier/HTMLDefinition.php
@@ -155,6 +155,7 @@ class HTMLPurifier_HTMLDefinition extends HTMLPurifier_Definition
     
     /** PUBLIC BUT INTERNAL VARIABLES */
     
+    var $type = 'HTML';
     var $manager; /**< Instance of HTMLPurifier_HTMLModuleManager */
     
     /**
@@ -164,44 +165,6 @@ class HTMLPurifier_HTMLDefinition extends HTMLPurifier_Definition
         $this->manager = new HTMLPurifier_HTMLModuleManager();
     }
     
-    /**
-     * Retrieve definition object from cache
-     */
-    function getCache($config) {
-        static $cache = array();
-        $file = HTMLPurifier_HTMLDefinition::getCacheFile($config);
-        if (isset($cache[$file])) return $cache[$file]; // unit test optimization
-        if (!file_exists($file)) return false;
-        $cache[$file] = unserialize(file_get_contents($file));
-        return $cache[$file];
-    }
-    
-    /**
-     * Determines a cache key identifier for a particular configuration
-     */
-    function getCacheKey($config) {
-        return md5(serialize(array($config->getBatch('HTML'), $config->getBatch('Attr'))));
-    }
-    
-    /**
-     * Determines file a particular configuration's definition is stored in
-     */
-    function getCacheFile($config) {
-        $key = HTMLPurifier_HTMLDefinition::getCacheKey($config);
-        return dirname(__FILE__) . '/HTMLDefinition/' . $key . '.ser';
-    }
-    
-    /**
-     * Saves HTMLDefinition to cache
-     */
-    function saveCache($config) {
-        $file = $this->getCacheFile($config);
-        $contents = serialize($this);
-        $fh = fopen($file, 'w');
-        fwrite($fh, $contents);
-        fclose($fh);
-    }
-    
     function doSetup($config) {
         $this->processModules($config);
         $this->setupConfigStuff($config);
diff --git a/tests/HTMLPurifier/ConfigTest.php b/tests/HTMLPurifier/ConfigTest.php
index 5952d2f4..8a5aeeb9 100644
--- a/tests/HTMLPurifier/ConfigTest.php
+++ b/tests/HTMLPurifier/ConfigTest.php
@@ -262,7 +262,7 @@ class HTMLPurifier_ConfigTest extends UnitTestCase
     }
     
     function test_getCSSDefinition() {
-        $this->old_copy = CS::instance($this->old_copy);
+        $this->old_copy = HTMLPurifier_ConfigSchema::instance($this->old_copy);
         
         $config = HTMLPurifier_Config::createDefault();
         $config->autoFinalize = false;
diff --git a/tests/HTMLPurifier/DefinitionCache/SerializerTest.php b/tests/HTMLPurifier/DefinitionCache/SerializerTest.php
new file mode 100644
index 00000000..16ada892
--- /dev/null
+++ b/tests/HTMLPurifier/DefinitionCache/SerializerTest.php
@@ -0,0 +1,177 @@
+<?php
+
+require_once 'HTMLPurifier/DefinitionCache/Serializer.php';
+
+class HTMLPurifier_Definition_SerializerMock extends HTMLPurifier_Definition
+{
+    
+    var $_test;
+    var $_expect = false;
+    
+    function HTMLPurifier_Definition_SerializerMock(&$test_case) {
+        $this->_test =& $test_case;
+    }
+    
+    function expectDoSetupOnce() {$this->_expect = true;}
+    
+    function doSetup($config) {
+        if ($this->_expect) {
+            $this->_test->pass();
+        } else {
+            $this->_test->fail('Unexpected call to doSetup');
+        }
+        unset($this->_test, $this->_expect);
+    }
+    
+}
+
+class HTMLPurifier_DefinitionCache_SerializerTest extends UnitTestCase
+{
+    
+    function test__SerializerMock_pass() {
+        $config = 'config';
+        generate_mock_once('UnitTestCase');
+        $test =& new UnitTestCaseMock($this);
+        $test->expectOnce('pass');
+        $mock = new HTMLPurifier_Definition_SerializerMock($test);
+        $mock->expectDoSetupOnce();
+        $mock->doSetup($config);
+    }
+    
+    function test__SerializerMock_fail() {
+        $config = 'config';
+        generate_mock_once('UnitTestCase');
+        $test =& new UnitTestCaseMock($this);
+        $test->expectOnce('fail');
+        $mock = new HTMLPurifier_Definition_SerializerMock($test);
+        $mock->doSetup($config);
+    }
+    
+    function test() {
+        
+        $cache = new HTMLPurifier_DefinitionCache_Serializer('Test');
+        
+        $config_array = array('Foo' => 'Bar');
+        $config_md5   = md5(serialize($config_array));
+        
+        $file = realpath(
+            $rel_file = dirname(__FILE__) .
+            '/../../../library/HTMLPurifier/DefinitionCache/Serializer/Test/' .
+            $config_md5 . '.ser'
+        );
+        if($file) unlink($file); // prevent previous failures from causing problems
+        
+        $config = $this->generateConfigMock($config_array);
+        $this->assertIdentical($config_md5, $cache->generateKey($config));
+        
+        $def_original = $this->generateDefinition();
+        
+        $cache->add($def_original, $config);
+        $this->assertFileExist($rel_file);
+        
+        $file_generated = $cache->generateFilePath($config);
+        $this->assertIdentical(realpath($rel_file), realpath($file_generated));
+        
+        $def_1 = $cache->get($config);
+        $this->assertIdentical($def_original, $def_1);
+        
+        $def_original->info_random = 'changed';
+        
+        $cache->set($def_original, $config);
+        $def_2 = $cache->get($config);
+        
+        $this->assertIdentical($def_original, $def_2);
+        $this->assertNotEqual ($def_original, $def_1);
+        
+        $def_original->info_random = 'did it change?';
+        
+        $this->assertFalse($cache->add($def_original, $config));
+        $def_3 = $cache->get($config);
+        
+        $this->assertNotEqual ($def_original, $def_3); // did not change!
+        $this->assertIdentical($def_3, $def_2);
+        
+        $cache->remove($config);
+        $this->assertFileNotExist($file);
+        
+        $def_4 = $cache->get($config);
+        $this->assertFalse($def_4);
+        
+    }
+    
+    function test_errors() {
+        /*$cache = new HTMLPurifier_DefinitionCache_Serializer('Test');
+        $def = new HTMLPurifier_Definition();
+        $def->setup = true;
+        $def->type = 'NotTest';
+        
+        $this->expectError('Cannot add definition of type NotTest to cache for Test');*/
+    }
+    
+    function test_flush() {
+        /*
+        $cache = new HTMLPurifier_DefinitionCache_Serializer();
+        
+        $config1 = $this->generateConfigMock(array('Candles' => 1));
+        $config2 = $this->generateConfigMock(array('Candles' => 2));
+        $config3 = $this->generateConfigMock(array('Candles' => 3));
+        
+        $def1 = $this->generateDefinition(array('info_candles' => 1));
+        $def2 = $this->generateDefinition(array('info_candles' => 2));
+        $def3 = $this->generateDefinition(array('info_candles' => 3));
+        
+        $cache->add($def1, $config1);
+        $cache->add($def2, $config2);
+        $cache->add($def3, $config3);
+        
+        $this->assertTrue($cache->get('Test', $config1));
+        $this->assertTrue($cache->get('Test', $config2));
+        $this->assertTrue($cache->get('Test', $config3));
+        
+        $cache->flush('Test');
+        */
+    }
+    
+    /**
+     * Generate a configuration mock object that returns $values
+     * to a getBatch() call
+     * @param $values Values to return when getBatch is invoked
+     */
+    function generateConfigMock($values) {
+        generate_mock_once('HTMLPurifier_Config');
+        $config = new HTMLPurifier_ConfigMock($this);
+        $config->setReturnValue('getBatch', $values, array('Test'));
+        return $config;
+    }
+    
+    /**
+     * Returns an anonymous def that has been setup and named Test
+     */
+    function generateDefinition($member_vars = array()) {
+        $def = new HTMLPurifier_Definition();
+        $def->setup = true;
+        $def->type  = 'Test';
+        foreach ($member_vars as $key => $val) {
+            $def->$key = $val;
+        }
+        return $def;
+    }
+    
+    /**
+     * Asserts that a file exists, ignoring the stat cache
+     */
+    function assertFileExist($file) {
+        clearstatcache();
+        $this->assertTrue(file_exists($file), 'Expected ' . $file . ' exists');
+    }
+    
+    /**
+     * Asserts that a file does not exist, ignoring the stat cache
+     */
+    function assertFileNotExist($file) {
+        $this->assertFalse(file_exists($file), 'Expected ' . $file . ' does not exist');
+    }
+    
+}
+
+?>
\ No newline at end of file
diff --git a/tests/HTMLPurifier/DefinitionCacheTest.php b/tests/HTMLPurifier/DefinitionCacheTest.php
new file mode 100644
index 00000000..0d1f512e
--- /dev/null
+++ b/tests/HTMLPurifier/DefinitionCacheTest.php
@@ -0,0 +1,14 @@
+<?php
+
+require_once 'HTMLPurifier/DefinitionCache.php';
+
+class HTMLPurifier_DefinitionCacheTest extends UnitTestCase
+{
+    function test_create() {
+        $config = HTMLPurifier_Config::createDefault();
+        $cache  = HTMLPurifier_DefinitionCache::create('Test', $config);
+        $this->assertEqual($cache, new HTMLPurifier_DefinitionCache_Serializer('Test'));
+    }
+}
+
+?>
\ No newline at end of file
diff --git a/tests/test_files.php b/tests/test_files.php
index cb184154..03761564 100644
--- a/tests/test_files.php
+++ b/tests/test_files.php
@@ -58,6 +58,8 @@ $test_files[] = 'ChildDef/TableTest.php';
 $test_files[] = 'ConfigSchemaTest.php';
 $test_files[] = 'ConfigTest.php';
 $test_files[] = 'ContextTest.php';
+$test_files[] = 'DefinitionCacheTest.php';
+$test_files[] = 'DefinitionCache/SerializerTest.php';
 $test_files[] = 'DefinitionTest.php';
 $test_files[] = 'DoctypeRegistryTest.php';
 $test_files[] = 'ElementDefTest.php';