diff --git a/application/models/user_model.php b/application/models/user_model.php
index ccc3d752..690cd4da 100644
--- a/application/models/user_model.php
+++ b/application/models/user_model.php
@@ -1,5 +1,12 @@
 <?php
 
+/* user_model.php
+ *
+ * This model implements user authentication and authorization
+ *
+ */
+ 
+
 // Uses 'phpass' from http://www.openwall.com/phpass/ to implement password hashing
 require_once('application/third_party/PasswordHash.php');
 
@@ -11,6 +18,7 @@ class User_Model extends CI_Model {
         parent::__construct();
     }
 
+	// FUNCTION: object get($username)
 	// Retrieve a user
 	function get($username) {
 		$this->db->where('user_name', $username);
@@ -18,12 +26,16 @@ class User_Model extends CI_Model {
 		return $r;
 	}
 
+	// FUNCTION: object get_by_id($id)
+	// Retrieve a user by user ID
 	function get_by_id($id) {
 		$this->db->where('user_id', $id);
 		$r = $this->db->get($this->config->item('auth_table'));
 		return $r;
 	}
 
+	// FUNCTION: bool exists($username)
+	// Check if a user exists (by username)
 	function exists($username) {
 		if($this->get($username)->num_rows == 0) {
 			return 0;
@@ -32,6 +44,8 @@ class User_Model extends CI_Model {
 		}
 	}
 
+	// FUNCTION: bool add($username, $password, $email, $type)
+	// Add a user
 	function add($username, $password, $email, $type) {
 		if(!$this->exists($username)) {
 			$data = array(
@@ -48,6 +62,9 @@ class User_Model extends CI_Model {
 		}
 	}
 
+	// FUNCTION: void edit()
+	// Edit a user
+	// TODO: This should return bool TRUE/FALSE or 0/1
 	function edit() {
 		
 		$data = array(
@@ -66,6 +83,9 @@ class User_Model extends CI_Model {
 
 	}
 
+	// FUNCTION: bool login()
+	// Validates a username/password combination
+	// This is really just a wrapper around User_Model::authenticate
 	function login() {
 		
 		$username = $this->input->post('user_name');
@@ -74,12 +94,18 @@ class User_Model extends CI_Model {
 		return $this->authenticate($username, $password);
 	}
 
+	// FUNCTION: void clear_session()
+	// Clears a user's login session
+	// Nothing is returned - it can be assumed that if this is called, the user's
+	// login session *will* be cleared, no matter what state it is in
 	function clear_session() {
 	
 		$this->session->unset_userdata(array('user_id' => '', 'user_type' => '', 'user_email' => '', 'user_hash' => ''));
-
 	}
 		
+	// FUNCTION: void update_session()
+	// Updates a user's login session after they've logged in
+	// TODO: This should return bool TRUE/FALSE or 0/1
 	function update_session($id) {
 		
 		$u = $this->get_by_id($id);
@@ -94,6 +120,9 @@ class User_Model extends CI_Model {
 		$this->session->set_userdata($userdata);
 	}
 
+	// FUNCTION: bool validate_session()
+	// Validate a user's login session
+	// If the user's session is corrupted in any way, it will clear the session
 	function validate_session() {
 
 		if($this->session->userdata('user_id'))
@@ -113,6 +142,8 @@ class User_Model extends CI_Model {
 		}
 	}
 
+	// FUNCTION: bool authenticate($username, $password)
+	// Authenticate a user against the users table
 	function authenticate($username, $password) {
 		$u = $this->get($username);
 		if($u->num_rows != 0)
@@ -124,6 +155,8 @@ class User_Model extends CI_Model {
 		return 0;
 	}
 
+	// FUNCTION: bool authorize($level)
+	// Checks a user's level of access against the given $level
 	function authorize($level) {
 		$u = $this->get_by_id($this->session->userdata('user_id'));
 		if(($this->validate_session) && ($u->row()->user_type >= $level)) {
@@ -133,17 +166,25 @@ class User_Model extends CI_Model {
 		}
 	}
 
+	// FUNCTION: bool set($username, $data)
+	// Updates a user's record in the database
+	// TODO: This returns TRUE/1 no matter what at the moment - should
+	// TODO: return TRUE/FALSE or 0/1 depending on success/failure
 	function set($username, $data) {
 		$this->db->where('user_name', $username);
 		$this->db->update($this->config->item('auth_table', $data));
 		return 1;
 	}
 
+	// FUNCTION: object users()
+	// Returns a list of users
 	function users() {
 		$r = $this->db->get($this->config->item('auth_table'));
 		return $r;
 	}
 
+	// FUNCTION: bool _auth($password, $hash)
+	// Checks a password against the stored hash
 	private function _auth($password, $hash) {
 		$h = new PasswordHash(8, FALSE);
 		if($h->CheckPassword($password, $hash)) {
@@ -153,6 +194,10 @@ class User_Model extends CI_Model {
 		}
 	}
 
+	// FUNCTION: string _hash($password)
+	// Returns a hashed version of the supplied $password
+	// Will return '0' in the event of problems with the
+	// hashing function
 	private function _hash($password) {
 		$h = new PasswordHash(8, FALSE);
 		$hash = $h->HashPassword($password);