diff --git a/src/helma/framework/core/Prototype.java b/src/helma/framework/core/Prototype.java
index 203927e8..a5815ef7 100644
--- a/src/helma/framework/core/Prototype.java
+++ b/src/helma/framework/core/Prototype.java
@@ -24,6 +24,11 @@ public final class Prototype {
 
     String name;
     Application app;
+    File directory;
+    
+    File [] files;
+    long lastDirectoryListing;
+    long checksum;
 
     HashMap code, zippedCode;
     HashMap skins, zippedSkins;
@@ -36,7 +41,7 @@ public final class Prototype {
     DbMapping dbmap;
 
     // lastCheck is the time the prototype's files were last checked
-    private long lastCheck;
+    private long lastChecksum;
     // lastUpdate is the time at which any of the prototype's files were
     // found updated the last time
     private long lastUpdate;
@@ -47,10 +52,11 @@ public final class Prototype {
     // as opposed to a Helma objectmodel node object.
     boolean isJavaPrototype;
 
-    public Prototype (String name, Application app) {
+    public Prototype (String name, File dir, Application app) {
 	// app.logEvent ("Constructing Prototype "+app.getName()+"/"+name);
 	this.app = app;
 	this.name = name;
+	this.directory = dir;
 
 	code = new HashMap ();
 	zippedCode = new HashMap ();
@@ -61,7 +67,7 @@ public final class Prototype {
 	skinMap = new SkinMap ();
 
 	isJavaPrototype = app.isJavaPrototype (name);
-	lastUpdate = lastCheck = 0;
+	lastUpdate = lastChecksum = 0;
     }
 
     /**
@@ -71,6 +77,43 @@ public final class Prototype {
 	return app;
     }
 
+    /**
+     *  Return this prototype's directory.
+     */
+    public File getDirectory () {
+	return directory;
+    }
+
+    /**
+     *  Get the list of files in this prototype's directory
+     */
+    public File[] getFiles () {
+	if (files == null || directory.lastModified() != lastDirectoryListing) {
+	    lastDirectoryListing = directory.lastModified ();
+	    files = directory.listFiles();
+	    if (files == null)
+	        files = new File[0];
+	}
+	return files;
+    }
+
+    /**
+     *  Get a checksum over the files in this prototype's directory
+     */
+    public long getChecksum () {
+    // long start = System.currentTimeMillis();
+	File[] f = getFiles ();
+	long c = 0;
+	for (int i=0; i<f.length; i++)
+	    c += f[i].lastModified();
+	checksum = c;
+    // System.err.println ("CHECKSUM "+name+": "+(System.currentTimeMillis()-start));
+	return checksum;
+    }
+    
+    public boolean isUpToDate () {
+	return checksum == lastChecksum;
+    }
 
     /**
      *  Set the parent prototype of this prototype, i.e. the prototype this
@@ -130,17 +173,6 @@ public final class Prototype {
 	return name;
     }
 
-    /* Updatable[] upd = null;
-    public Updatable[] getUpdatables () {
-	if (upd == null) {
-	    upd = new Updatable[updatables.size()];
-	    int i = 0;
-	    for (Iterator it = updatables.values().iterator(); it.hasNext(); ) {
-	        upd[i++] = (Updatable) it.next();
-	    }
-	}
-	return upd;
-    } */
 
     /**
      *  Get the last time any script has been re-read for this prototype.
@@ -162,18 +194,20 @@ public final class Prototype {
      *  Get the time at which this prototype's scripts were checked
      *  for changes for the last time.
      */
-    public long getLastCheck () {
+    /* public long getLastCheck () {
 	return lastCheck;
-    }
+    } */
 
     /**
      *  Signal that the prototype's scripts have been checked for
      *  changes.
      */
     public void markChecked () {
-	lastCheck = System.currentTimeMillis ();
+	// lastCheck = System.currentTimeMillis ();
+	lastChecksum = checksum;
     }
 
+
     /**
      *  Return a clone of this prototype's actions container. Synchronized
      *  to not return a map in a transient state where it is just being
@@ -381,7 +415,7 @@ public final class Prototype {
 
 
 	private void checkForUpdates () {
-	    if (lastCheck < System.currentTimeMillis()- 2000l)
+	    if (/* lastCheck < System.currentTimeMillis()- 2000l*/ !isUpToDate())
 	        app.typemgr.updatePrototype (Prototype.this);
 	    if (lastUpdate > lastSkinmapLoad)
 	        load ();
diff --git a/src/helma/framework/core/TypeManager.java b/src/helma/framework/core/TypeManager.java
index 97fd1102..60b329ba 100644
--- a/src/helma/framework/core/TypeManager.java
+++ b/src/helma/framework/core/TypeManager.java
@@ -24,6 +24,8 @@ public final class TypeManager {
     HashMap zipfiles;
     long lastCheck = 0;
     long appDirMod = 0;
+    // a checksum that changes whenever something in the application files changes.
+    long checksum;
 
     // the hopobject prototype
     Prototype hopobjectProto;
@@ -123,12 +125,16 @@ public final class TypeManager {
 	    }
 	}
 
+	// calculate this app's checksum by adding all checksums from all prototypes
+	long newChecksum = 0;
+
 	// loop through zip files to check for updates
 	for (Iterator it=zipfiles.values ().iterator (); it.hasNext (); ) {
 	    ZippedAppFile zipped = (ZippedAppFile) it.next ();
 	    if (zipped.needsUpdate ()) {
 	        zipped.update ();
 	    }
+	    newChecksum += zipped.lastmod;
 	}
 
 	// loop through prototypes and check if type.properties needs updates
@@ -136,6 +142,8 @@ public final class TypeManager {
 	// have been created in the previous loop.
 	for (Iterator i=prototypes.values().iterator(); i.hasNext(); ) {
 	    Prototype proto = (Prototype) i.next ();
+	    // calculate this app's type checksum
+	    newChecksum += proto.getChecksum();
 	    // update prototype's type mapping
 	    DbMapping dbmap = proto.getDbMapping ();
 	    if (dbmap != null && dbmap.needsUpdate ()) {
@@ -150,7 +158,7 @@ public final class TypeManager {
 	        }
 	    }
 	}
-
+	checksum = newChecksum;
     }
 
     protected void removeZipFile (String zipname) {
@@ -175,6 +183,14 @@ public final class TypeManager {
 	return true;
     }
 
+   /**
+    *  Return a checksum over all files in all prototypes in this application.
+    *  The checksum can be used to find out quickly if any file has changed.
+    */
+    public long getChecksum () {
+	return checksum;
+    }
+
     /**
     *   Get a prototype defined for this application
     */
@@ -184,7 +200,7 @@ public final class TypeManager {
 
     /**
      * Get a prototype, creating it if it doesn't already exist. Note
-     * that it doesn't create a DbMapping - this is left to the 
+     * that it doesn't create a DbMapping - this is left to the
      * caller (e.g. ZippedAppFile).
      */
     public Prototype createPrototype (String typename) {
@@ -196,7 +212,7 @@ public final class TypeManager {
      *  Create a prototype from a directory containing scripts and other stuff
      */
     public Prototype createPrototype (String typename, File dir) {
-	Prototype proto = new Prototype (typename, app);
+	Prototype proto = new Prototype (typename, dir, app);
 	// Create and register type properties file
 	File propfile = new File (dir, "type.properties");
 	SystemProperties props = new SystemProperties (propfile.getAbsolutePath ());
@@ -224,16 +240,16 @@ public final class TypeManager {
     * Update a prototype to the files in the prototype directory.
     */
     public void updatePrototype (Prototype proto) {
-        if (proto == null)
+        if (proto == null || proto.isUpToDate())
             return;
 
         synchronized (proto) {
             // check again because another thread may have checked the
             // prototype while we were waiting for access to the synchronized section
-            if (System.currentTimeMillis() - proto.getLastCheck() < 1000)
-                return;
+            /* if (System.currentTimeMillis() - proto.getLastCheck() < 1000)
+                return; */
 
-            File dir = new File (appDir, proto.getName());
+            File dir = proto.getDirectory ();
             HashSet updateSet = null;
             HashSet createSet = null;
 
@@ -249,10 +265,10 @@ public final class TypeManager {
             }
 
             // next we check if files have been created or removed since last update
-            if (proto.getLastCheck() < dir.lastModified ()) {
-                String[] list = dir.list();
+            // if (proto.getLastCheck() < dir.lastModified ()) {
+                File[] list = proto.getFiles();
                 for (int i=0; i<list.length; i++) {
-                    String fn = list[i];
+                    String fn = list[i].getName();
                     if (!proto.updatables.containsKey (fn)) {
                         if (fn.endsWith (templateExtension) ||
                             fn.endsWith (scriptExtension) ||
@@ -266,7 +282,7 @@ public final class TypeManager {
                         }
                     }
                 }
-            }
+            // }
 
             // if nothing needs to be updated, mark prototype as checked and return
             if (updateSet == null && createSet == null) {
@@ -278,34 +294,34 @@ public final class TypeManager {
             if (createSet != null) {
                 Object[] newFiles = createSet.toArray ();
                 for (int i=0; i<newFiles.length; i++) {
-                    String filename = (String) newFiles[i];
+                    File file = (File) newFiles[i];
+                    String filename = file.getName ();
                     int dot = filename.lastIndexOf (".");
                     String tmpname = filename.substring(0, dot);
-                    File tmpfile = new File (dir, filename);
 
                     if (filename.endsWith (templateExtension)) {
                         try {
-                            Template t = new Template (tmpfile, tmpname, proto);
+                            Template t = new Template (file, tmpname, proto);
                             proto.addTemplate (t);
                         } catch (Throwable x) {
                             app.logEvent ("Error updating prototype: "+x);
                         }
                     } else if (filename.endsWith (scriptExtension)) {
                         try {
-                            FunctionFile ff = new FunctionFile (tmpfile, proto);
+                            FunctionFile ff = new FunctionFile (file, proto);
                             proto.addFunctionFile (ff);
                         } catch (Throwable x) {
                             app.logEvent ("Error updating prototype: "+x);
                         }
                     }  else if (filename.endsWith (actionExtension)) {
                         try {
-                            ActionFile af = new ActionFile (tmpfile, tmpname, proto);
+                            ActionFile af = new ActionFile (file, tmpname, proto);
                             proto.addActionFile (af);
                         } catch (Throwable x) {
                             app.logEvent ("Error updating prototype: "+x);
                         }
                     }  else if (filename.endsWith (skinExtension)) {
-                        SkinFile sf = new SkinFile (tmpfile, tmpname, proto);
+                        SkinFile sf = new SkinFile (file, tmpname, proto);
                         proto.addSkinFile (sf);
                     }
                 }