diff --git a/backend/index.php b/backend/index.php
index 247d57e..2d70ee7 100644
--- a/backend/index.php
+++ b/backend/index.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * backend bootstrapping entrypoint
+ * Backend bootstrapping entrypoint
  *
  * @author Steffen Vogel <info@steffenvogel.de>
  * @copyright Copyright (c) 2010, The volkszaehler.org project
diff --git a/backend/lib/Controller/ChannelController.php b/backend/lib/Controller/ChannelController.php
index 0336e30..6617078 100644
--- a/backend/lib/Controller/ChannelController.php
+++ b/backend/lib/Controller/ChannelController.php
@@ -26,7 +26,7 @@ namespace Volkszaehler\Controller;
 use \Volkszaehler\Model;
 
 /**
- * channel controller
+ * Channel controller
  *
  * @author Steffen Vogel <info@steffenvogel.de>
  * @package default
@@ -34,9 +34,10 @@ use \Volkszaehler\Model;
 class ChannelController extends Controller {
 
 	/**
-	 * get channels by filter
+	 * Get channels by filter
 	 *
 	 * @todo authentification/indentification
+	 * @todo implement filters
 	 */
 	public function get() {
 		$dql = 'SELECT c FROM Volkszaehler\Model\Channel c';
@@ -62,7 +63,7 @@ class ChannelController extends Controller {
 	}
 
 	/**
-	 * add channel
+	 * Add channel
 	 *
 	 * @todo validate input and throw exceptions
 	 */
@@ -82,7 +83,7 @@ class ChannelController extends Controller {
 	}
 
 	/**
-	 * delete channel
+	 * Delete channel by uuid
 	 *
 	 * @todo authentification/indentification
 	 */
@@ -95,7 +96,7 @@ class ChannelController extends Controller {
 	}
 
 	/**
-	 * edit channel properties
+	 * Edit channel properties
 	 *
 	 * @todo authentification/indentification
 	 * @todo to be implemented
diff --git a/backend/lib/Controller/Controller.php b/backend/lib/Controller/Controller.php
index f660cc6..e2ed70b 100644
--- a/backend/lib/Controller/Controller.php
+++ b/backend/lib/Controller/Controller.php
@@ -24,7 +24,7 @@
 namespace Volkszaehler\Controller;
 
 /**
- * controller superclass for all controllers
+ * Controller superclass for all controllers
  *
  * @author Steffen Vogel <info@steffenvogel.de>
  * @package default
@@ -34,7 +34,10 @@ abstract class Controller {
 	protected $em;
 
 	/**
-	 * constructor
+	 * Constructor
+	 *
+	 * @param View $view
+	 * @param EntityManager $em
 	 */
 	public function __construct(\Volkszaehler\View\View $view, \Doctrine\ORM\EntityManager $em) {
 		$this->view = $view;
@@ -42,7 +45,7 @@ abstract class Controller {
 	}
 
 	/**
-	 * run controller actions
+	 * Run controller actions
 	 *
 	 * @param string $action runs the action if class method is available
 	 */
diff --git a/backend/lib/Controller/DataController.php b/backend/lib/Controller/DataController.php
index 6f2a242..cdda1e1 100644
--- a/backend/lib/Controller/DataController.php
+++ b/backend/lib/Controller/DataController.php
@@ -24,11 +24,10 @@
 namespace Volkszaehler\Controller;
 
 use Volkszaehler\Model;
-
 use Volkszaehler\Util;
 
 /**
- * data controller
+ * Data controller
  *
  * @author Steffen Vogel <info@steffenvogel.de>
  * @todo call via redirect from Controller\Channel
@@ -37,7 +36,7 @@ use Volkszaehler\Util;
 class DataController extends Controller {
 
 	/**
-	 * query for data
+	 * Query for data by given channel or group
 	 *
 	 * @todo authentification/indentification
 	 * @todo use uuids for groups or channels
@@ -72,7 +71,7 @@ class DataController extends Controller {
 	}
 
 	/**
-	 * log new readings
+	 * Log new readings with logger interfaces
 	 *
 	 * @todo authentification/indentification
 	 */
diff --git a/backend/lib/Controller/GroupController.php b/backend/lib/Controller/GroupController.php
index a1dba2b..388997c 100644
--- a/backend/lib/Controller/GroupController.php
+++ b/backend/lib/Controller/GroupController.php
@@ -24,7 +24,7 @@
 namespace Volkszaehler\Controller;
 
 /**
- * group controller
+ * Group controller
  *
  * @author Steffen Vogel (info@steffenvogel.de)
  * @package default
@@ -34,7 +34,7 @@ use Volkszaehler\Model;
 class GroupController extends Controller {
 
 	/**
-	 * get groups by filter
+	 * Get groups by filter
 	 *
 	 * @todo filter to root groups when using recursion
 	 */
@@ -63,7 +63,9 @@ class GroupController extends Controller {
 	}
 
 	/**
-	 * add new group as child of a parent group
+	 * Add new group as child of a parent group
+	 *
+	 * @todo add parent validation to model?
 	 */
 	public function add() {
 		$ugid = $this->view->request->getParameter('ugid');
diff --git a/backend/lib/DataAggregationIterator.php b/backend/lib/DataAggregationIterator.php
index 4fa9c7c..cb2dac9 100644
--- a/backend/lib/DataAggregationIterator.php
+++ b/backend/lib/DataAggregationIterator.php
@@ -23,17 +23,25 @@
 
 namespace Volkszaehler;
 
-/**
- * @author Steffen Vogel <info@steffenvogel.de>
- */
 use Doctrine\DBAL;
 
+/**
+ * @author Steffen Vogel <info@steffenvogel.de>
+ * @package default
+ */
 class DataAggregationIterator extends DataIterator {
 	protected $packageSize;		// count of readings in tuple
 	protected $aggregatedSize;	// total readings
 	protected $aggregatedKey = -1;
 
-	public function __construct(DBAL\Statement $stmt, $size, $tuples) {
+	/**
+	 * Constructor
+	 *
+	 * @param \PDOStatement $stmt
+	 * @param unknown_type $size
+	 * @param unknown_type $tuples
+	 */
+	public function __construct(\PDOStatement  $stmt, $size, $tuples) {
 		parent::__construct($stmt, $size);
 
 		if ($tuples < $this->size) {						// return $tuples values
@@ -47,7 +55,7 @@ class DataAggregationIterator extends DataIterator {
 	}
 
 	/**
-	 * aggregate data
+	 * Aggregate data
 	 */
 	public function next() {
 		$current = array (0, 0);
@@ -71,14 +79,26 @@ class DataAggregationIterator extends DataIterator {
 		$this->current[2] = $this->packageSize;
 	}
 
+	/**
+	 * @return array with data
+	 */
 	public function current() {
 		return $this->current;
 	}
 
+	/**
+	 * @return integer the nth data row
+	 */
 	public function key() {
 		return $this->aggregatedKey;
 	}
 
+	/**
+	 * Rewind the iterator
+	 *
+	 * Should only be called once
+	 * PDOStatements doest support rewind()
+	 */
 	public function rewind() {
 		parent::rewind();
 
@@ -90,7 +110,7 @@ class DataAggregationIterator extends DataIterator {
 	}
 
 	/**
-	 * getter & setter
+	 * Getter & setter
 	 */
 	public function getPackageSize() { return $this->packageSize; }
 }
diff --git a/backend/lib/DataIterator.php b/backend/lib/DataIterator.php
index 1bdf5a5..f9dbc64 100644
--- a/backend/lib/DataIterator.php
+++ b/backend/lib/DataIterator.php
@@ -23,49 +23,75 @@
 
 namespace Volkszaehler;
 
-/**
- * @author Steffen Vogel <info@steffenvogel.de>
- */
 use Doctrine\DBAL;
 
+/**
+ * @author Steffen Vogel <info@steffenvogel.de>
+ * @package default
+ */
 class DataIterator implements \Iterator, \Countable {
 	protected $current;
 	protected $key;			// incrementing key
-	protected $pdoStmt;		// PDOStatement
+	protected $stmt;		// PDOStatement
 	protected $size;	// total readings in PDOStatement
 
-	public function __construct(DBAL\Statement $stmt, $size) {
+	/**
+	 * Constructor
+	 *
+	 * @param \PDOStatement $stmt
+	 * @param unknown_type $size
+	 */
+	public function __construct(\PDOStatement $stmt, $size) {
 		$this->size = $size;
 
-		$this->pdoStmt = $stmt->getWrappedStatement();
-		$this->pdoStmt->setFetchMode(\PDO::FETCH_NUM);
+		$this->stmt = $stmt;
+		$this->stmt->setFetchMode(\PDO::FETCH_NUM);
 	}
 
+	/**
+	 * @return array with data
+	 */
 	public function current() {
 		return $this->current;
 	}
 
+	/**
+	 * Fetch next row from database
+	 */
 	public function next() {
 		$this->key++;
-		$this->current = $this->pdoStmt->fetch();
+		$this->current = $this->stmt->fetch();
+
 	}
 
+	/**
+	 * @return integer the nth data row
+	 */
 	public function key() {
 		return $this->key;
 	}
 
+	/**
+	 * @return boolean do we have another row in the resultset?
+	 */
 	public function valid() {
 		return (boolean) $this->current;
 	}
 
 	/**
-	 * NoRewindIterator
+	 * Rewind the iterator
+	 *
+	 * Should only be called once
+	 * PDOStatements doest support rewind()
 	 */
 	public function rewind() {
 		$this->key = 0;
-		$this->current = $this->pdoStmt->fetch();
+		$this->current = $this->stmt->fetch();
 	}
 
+	/**
+	 * @return integer
+	 */
 	public function count() { return $this->size; }
 }
 
diff --git a/backend/lib/Dispatcher.php b/backend/lib/Dispatcher.php
index 4dd977d..f9a1ac6 100644
--- a/backend/lib/Dispatcher.php
+++ b/backend/lib/Dispatcher.php
@@ -29,16 +29,16 @@ use Volkszaehler\Controller;
 use Volkszaehler\Util;
 
 /**
- * backend dispatcher
+ * Backend dispatcher
  *
- * this class acts as a frontcontroller to route incomming requests
+ * This class acts as a frontcontroller to route incomming requests
  *
  * @package default
  * @author Steffen Vogel <info@steffenvogel.de>
  */
 class Dispatcher {
 	/**
-	 * @var \Doctrine\ORM\EntityManager Doctrine Model
+	 * @var \Doctrine\ORM\EntityManager Doctrine EntityManager
 	 */
 	protected $em;
 
@@ -68,18 +68,24 @@ class Dispatcher {
 	);
 
 	/**
-	 * constructor
+	 * Constructor
 	 */
 	public function __construct() {
 		// create HTTP request & response (needed to initialize view & controller)
 		$request = new HTTP\Request();
 		$response = new HTTP\Response();
 
-		if (!($format = $request->getParameter('format'))) {
+		if ($format = $request->getParameter('format')) {
+			$format = strtolower($format);
+		}
+		else {
 			$format = 'json';	// default view
 		}
 
-		if (!($controller = $request->getParameter('controller'))) {
+		if ($controller = $request->getParameter('controller')) {
+			$controller = strtolower($controller);
+		}
+		else {
 			throw new \Exception('no controller specified');
 		}
 
@@ -124,7 +130,7 @@ class Dispatcher {
 		}
 
 		// initialize controller
-		$controllerClassName = 'Volkszaehler\Controller\\' . ucfirst($request->getParameter('controller')) . 'Controller';
+		$controllerClassName = 'Volkszaehler\Controller\\' . ucfirst($controller) . 'Controller';
 		if (!(Util\ClassLoader::classExists($controllerClassName)) || !is_subclass_of($controllerClassName, '\Volkszaehler\Controller\Controller')) {
 			throw new \Exception('\'' . $controllerClassName . '\' is not a valid controller');
 		}
@@ -132,7 +138,7 @@ class Dispatcher {
 	}
 
 	/**
-	 * execute application
+	 * Execute application
 	 */
 	public function run() {
 		if ($this->view->request->getParameter('action')) {
@@ -155,7 +161,7 @@ class Dispatcher {
 	}
 
 	/**
-	 * factory for doctrines entitymanager
+	 * Factory for doctrines entitymanager
 	 *
 	 * @todo create extra singleton class?
 	 */
diff --git a/backend/lib/Interpreter/GroupInterpreter.php b/backend/lib/Interpreter/GroupInterpreter.php
index 8a41fce..3276de6 100644
--- a/backend/lib/Interpreter/GroupInterpreter.php
+++ b/backend/lib/Interpreter/GroupInterpreter.php
@@ -26,9 +26,27 @@ namespace Volkszaehler\Interpreter;
 use Doctrine\ORM;
 use Volkszaehler\Model;
 
+/**
+ * Group interpreter
+ *
+ * The GroupInterpreter is used to aggregate multiple channels with the same
+ * indicator
+ *
+ * @author Steffen Vogel <info@steffenvogel.de>
+ * @package default
+ *
+ */
 class GroupInterpreter {
 	protected $channelInterpreter;
 
+	/**
+	 * Constructor
+	 *
+	 * @param Model\Group $group should only contain channels with the same indicator
+	 * @param ORM\EntityManager $em
+	 * @param integer $from timestamp in ms since 1970
+	 * @param integer $to timestamp in ms since 1970
+	 */
 	public function __construct(Model\Group $group, ORM\EntityManager $em, $from, $to) {
 		foreach ($group->getChannels() as $channel) {
 			if (isset($indicator) && $indicator != $channel->getIndicator) {
@@ -43,15 +61,20 @@ class GroupInterpreter {
 	}
 
 	/**
+	 * Just a passthrough to the channel interpreters
 	 *
+	 * @param string|integer $groupBy
 	 * @todo to be implemented
+	 * @return array of values
 	 */
 	public function getValues($groupBy = NULL) {
 
 	}
 
 	/**
+	 * Just a passthrough to the channel interpreters
 	 *
+	 * @return array with the smallest value
 	 */
 	public function getMin() {
 		$min = current($this->channelInterpreter)->getMax();
@@ -65,7 +88,9 @@ class GroupInterpreter {
 	}
 
 	/**
+	 * Just a passthrough to the channel interpreters
 	 *
+	 * @return array with the biggest value
 	 */
 	public function getMax() {
 		$max = current($this->channelInterpreter)->getMax();
@@ -79,7 +104,9 @@ class GroupInterpreter {
 	}
 
 	/**
+	 * Just a passthrough to the channel interpreters
 	 *
+	 * @return float average value
 	 */
 	public function getAverage() {
 		$sum = 0;
diff --git a/backend/lib/Interpreter/Interpreter.php b/backend/lib/Interpreter/Interpreter.php
index b53eabc..adb6a07 100644
--- a/backend/lib/Interpreter/Interpreter.php
+++ b/backend/lib/Interpreter/Interpreter.php
@@ -42,7 +42,7 @@ interface InterpreterInterface {
 }
 
 /**
- * interpreter superclass for all interpreters
+ * Interpreter superclass for all interpreters
  *
  * @author Steffen Vogel <info@steffenvogel.de>
  * @package default
@@ -56,9 +56,12 @@ abstract class Interpreter implements InterpreterInterface {
 	protected $to;
 
 	/**
+	 * Constructor
 	 *
-	 * @param $channel
-	 * @param $em
+	 * @param Channel $channel
+	 * @param EntityManager $em
+	 * @param integer $from timestamp in ms since 1970
+	 * @param integer $to timestamp in ms since 1970
 	 */
 	public function __construct(\Volkszaehler\Model\Channel $channel, \Doctrine\ORM\EntityManager $em, $from = NULL, $to = NULL) {
 		$this->channel = $channel;
@@ -69,11 +72,10 @@ abstract class Interpreter implements InterpreterInterface {
 	}
 
 	/**
+	 * Get raw data
 	 *
-	 * @param integer $from timestamp in ms since 1970
-	 * @param integer $to timestamp in ms since 1970
-	 * @param mixed $groupBy
-	 * @todo split in two functions
+	 * @param string|integer $groupBy
+	 * @return Volkszaehler\DataIterator
 	 */
 	protected function getData($groupBy = NULL) {
 		// get dbal connection from EntityManager
@@ -98,8 +100,7 @@ abstract class Interpreter implements InterpreterInterface {
 
 		$rowCount = $conn->fetchColumn($sqlRowCount, $params, 0);
 
-		$stmt = $conn->prepare('SELECT ' . $sqlFields . $sqlFrom . $sqlWhere . $sqlGroupBy . $sqlOrderBy);
-		$stmt->execute($params);
+		$stmt = $conn->executeQuery('SELECT ' . $sqlFields . $sqlFrom . $sqlWhere . $sqlGroupBy . $sqlOrderBy, $params);
 
 		if ($sqlGroupBy || is_null($groupBy)) {		// aggregation by sql or skip it
 			return new Volkszaehler\DataIterator($stmt, $rowCount);
@@ -114,10 +115,10 @@ abstract class Interpreter implements InterpreterInterface {
 	}
 
 	/**
-	 * builds sql query part for grouping data by date functions
+	 * Builds sql query part for grouping data by date functions
 	 *
 	 * @param string $groupBy
-	 * @return string $sql the sql part
+	 * @return string the sql part
 	 * @todo make compatible with: MSSql (Transact-SQL), Sybase, Firebird/Interbase, IBM, Informix, MySQL, Oracle, DB2, PostgreSQL, SQLite
 	 */
 	protected static function buildGroupBySQL($groupBy) {
@@ -157,6 +158,13 @@ abstract class Interpreter implements InterpreterInterface {
 		}
 	}
 
+	/**
+	 * Build sql query part to filter specified time interval
+	 *
+	 * @param integer $from timestamp in ms since 1970
+	 * @param integer $to timestamp in ms since 1970
+	 * @return string the sql part
+	 */
 	protected static function buildTimeFilterSQL($from = NULL, $to = NULL) {
 		$sql = '';
 
diff --git a/backend/lib/Interpreter/MeterInterpreter.php b/backend/lib/Interpreter/MeterInterpreter.php
index a708b3d..a8babf2 100644
--- a/backend/lib/Interpreter/MeterInterpreter.php
+++ b/backend/lib/Interpreter/MeterInterpreter.php
@@ -24,7 +24,7 @@
 namespace Volkszaehler\Interpreter;
 
 /**
- * meter interpreter
+ * Meter interpreter
  *
  * @package default
  * @author Steffen Vogel (info@steffenvogel.de)
@@ -35,7 +35,7 @@ use Volkszaehler;
 class MeterInterpreter extends Interpreter {
 
 	/**
-	 * calculates the consumption for interval speciefied by $from and $to
+	 * Calculates the consumption for interval speciefied by $from and $to
 	 *
 	 * @todo untested
 	 */
@@ -68,7 +68,7 @@ class MeterInterpreter extends Interpreter {
 	}
 
 	/**
-	 * @return Ambigous <mixed, unknown>
+	 * @return array
 	 */
 	public function getMax() {
 		$data = $this->getData();
@@ -84,20 +84,21 @@ class MeterInterpreter extends Interpreter {
 
 	/**
 	 * @todo calculate timeinterval if no params were given
+	 * @return float
 	 */
 	public function getAverage() {
 		return $this->getConsumption() / ($this->to - $this->from) / 1000;	// return W
 	}
 
 	/**
-	 * just a passthrough of raw data
+	 * Just a passthrough of raw data
 	 */
 	public function getPulses($groupBy = NULL) {
 		return parent::getData($groupBy);
 	}
 
 	/**
-	 * raw pulses to power conversion
+	 * Raw pulses to power conversion
 	 *
 	 * @todo untested
 	 * @return array with timestamp and values in [W]
@@ -114,8 +115,8 @@ class MeterInterpreter extends Interpreter {
 
 				$values[] = array(
 					(int) ($pulse[0] - $delta / 2),															// timestamp
-					round($pulse[1] * (3600000 / (($this->channel->getResolution() / 1000) * $delta)), 5),	// value
-					$pulse[2]
+					$pulse[1] * (3600000 / (($this->channel->getResolution() / 1000) * $delta)),	// value
+					(isset($pulse[2])) ? $pulse[2] : 1
 				);
 			}
 			else {
diff --git a/backend/lib/Interpreter/SensorInterpreter.php b/backend/lib/Interpreter/SensorInterpreter.php
index d310237..53bcb80 100644
--- a/backend/lib/Interpreter/SensorInterpreter.php
+++ b/backend/lib/Interpreter/SensorInterpreter.php
@@ -24,7 +24,7 @@
 namespace Volkszaehler\Interpreter;
 
 /**
- * sensor interpreter
+ * Sensor interpreter
  *
  * @package default
  * @author Steffen Vogel <info@steffenvogel.de>
@@ -33,6 +33,7 @@ class SensorInterpreter extends Interpreter {
 
 	/**
 	 * @todo untested
+	 * @param string|integer $groupBy
 	 */
 	public function getValues($groupBy = NULL) {
 		$data = parent::getData($groupBy);
@@ -52,6 +53,7 @@ class SensorInterpreter extends Interpreter {
 	/**
 	 * @todo adapt to doctrine orm
 	 * @todo untested
+	 * @return array
 	 */
 	public function getMin() {
 		return $this->dbh->query('SELECT value, timestamp FROM data WHERE channel_id = ' . (int) $this->id . self::buildFilterTime($this->from, $this->to) . ' ORDER BY value ASC', 1)->current();
@@ -60,6 +62,7 @@ class SensorInterpreter extends Interpreter {
 	/**
 	 * @todo adapt to doctrine orm
 	 * @todo untested
+	 * @return array
 	 */
 	public function getMax() {
 		return $this->dbh->query('SELECT value, timestamp FROM data WHERE channel_id = ' . (int) $this->id . self::buildFilterTime($this->from, $this->to) . ' ORDER BY value DESC', 1)->current();
@@ -68,6 +71,7 @@ class SensorInterpreter extends Interpreter {
 	/**
 	 * @todo adapt to doctrine orm
 	 * @todo untested
+	 * @return float
 	 */
 	public function getAverage() {
 		return $this->dbh->query('SELECT AVG(value) AS value FROM data WHERE channel_id = ' . (int) $this->id . self::buildFilterTime($this->from, $this->to))->current();
@@ -75,6 +79,7 @@ class SensorInterpreter extends Interpreter {
 
 	/**
 	 * @todo to be implemented
+	 * @return float
 	 */
 	public function getConsumption() {
 
diff --git a/backend/lib/Logger/FluksoLogger.php b/backend/lib/Logger/FluksoLogger.php
index 1a786ac..95f2f3e 100644
--- a/backend/lib/Logger/FluksoLogger.php
+++ b/backend/lib/Logger/FluksoLogger.php
@@ -24,7 +24,7 @@
 namespace Volkszaehler\Logger;
 
 /**
- * logger for the Flukso.net API
+ * Logger for the Flukso.net API
  *
  * @package default
  * @link http://www.flukso.net
diff --git a/backend/lib/Logger/Logger.php b/backend/lib/Logger/Logger.php
index 48ba52b..a7a6989 100644
--- a/backend/lib/Logger/Logger.php
+++ b/backend/lib/Logger/Logger.php
@@ -28,7 +28,7 @@ use Doctrine\ORM;
 use Volkszaehler\Model;
 
 /**
- * interface for parsing diffrent logging APIs (google, flukso etc..)
+ * Interface for parsing diffrent logging APIs (google, flukso etc..)
  *
  * @author Steffen Vogel <info@steffenvogel.de>
  * @package default
@@ -45,15 +45,29 @@ interface LoggerInterface {
 	public function getVersion();
 }
 
+/**
+ *
+ * @author Steffen Vogel <info@steffenvogel.de>
+ *
+ */
 abstract class Logger implements LoggerInterface {
 	protected $request;
 	protected $em;
 
+	/**
+	 * Constructor
+	 *
+	 * @param HTTP\Request $request
+	 * @param ORM\EntityManager $em
+	 */
 	public function __construct(HTTP\Request  $request, ORM\EntityManager $em) {
 		$this->request = $request;
 		$this->em = $em;
 	}
 
+	/**
+	 *
+	 */
 	public function log() {
 		$data = $this->getData();
 
diff --git a/backend/lib/Logger/PrototypeLogger.php b/backend/lib/Logger/PrototypeLogger.php
index 638b52f..1703514 100644
--- a/backend/lib/Logger/PrototypeLogger.php
+++ b/backend/lib/Logger/PrototypeLogger.php
@@ -27,7 +27,7 @@ use Volkszaehler\Model;
 use Doctrine\ORM;
 
 /**
- * logger for the the original volkszaehler.org prototype based on ethersex's watchasync
+ * Logger for the the original volkszaehler.org prototype based on ethersex's watchasync
  *
  * @package default
  * @link http://github.com/ethersex/ethersex/blob/master/services/watchasync
@@ -67,7 +67,7 @@ class PrototypeLogger extends Logger {
 }
 
 /*
- * just some documentation
+ * Just some documentation
  *
  * /httplog/httplog.php?port=<port>&uuid=<uuid>&time=<unixtimestamp>
  *
diff --git a/backend/lib/Logger/VzLogger.php b/backend/lib/Logger/VzLogger.php
index 6f0ab3d..7929c04 100644
--- a/backend/lib/Logger/VzLogger.php
+++ b/backend/lib/Logger/VzLogger.php
@@ -50,6 +50,9 @@ class VzLogger extends Logger {
 		$data = new Model\Data($channel, $value, $ts);
 	}
 
+	/**
+	 * @return string the version
+	 */
 	public function getVersion() {
 		return $this->request->getParameter('version');
 	}
diff --git a/backend/lib/Model/Channel.php b/backend/lib/Model/Channel.php
index 8702570..18e844b 100644
--- a/backend/lib/Model/Channel.php
+++ b/backend/lib/Model/Channel.php
@@ -86,7 +86,7 @@ class Channel extends Entity {
 	}
 
 	/**
-	 * add a new data to the database
+	 * Add a new data to the database
 	 * @todo move to Logger\Logger?
 	 */
 	public function addData(\Volkszaehler\Model\Data $data) {
@@ -94,13 +94,29 @@ class Channel extends Entity {
 	}
 
 	/**
-	 * obtain channels data interpreter to calculate statistical information
+	 * Obtain channel interpreter to obtain data and statistical information for a given time interval
+	 *
+	 * @param Doctrine\ORM\EntityManager $em
+	 * @param integer $from timestamp in ms since 1970
+	 * @param integer $to timestamp in ms since 1970
+	 * @return Interpreter
 	 */
 	public function getInterpreter(\Doctrine\ORM\EntityManager $em, $from, $to) {
 		$interpreterClassName = 'Volkszaehler\Interpreter\\' . ucfirst($this->getType()) . 'Interpreter';
 		return new $interpreterClassName($this, $em, $from, $to);
 	}
 
+	/**
+	 * Validate
+	 *
+	 * @PrePersist @PreUpdate
+	 */
+	protected function validate() {
+		if ($this->getResolution() <= 0 && $this->getType() == 'meter') {
+			throw new Exception('resolution has to be a positive integer');
+		}
+	}
+
 	/**
 	 * getter & setter
 	 */
diff --git a/backend/lib/Model/Entity.php b/backend/lib/Model/Entity.php
index 6b5fa2d..6a39c85 100644
--- a/backend/lib/Model/Entity.php
+++ b/backend/lib/Model/Entity.php
@@ -26,7 +26,7 @@ namespace Volkszaehler\Model;
 use Volkszaehler\Util;
 
 /**
- * entity superclass for all models with database persistance
+ * Entity superclass for all models with database persistance
  *
  * @author Steffen Vogel <info@steffenvogel.de>
  * @package default
@@ -49,7 +49,7 @@ abstract class Entity {
 	}
 
 	/**
-	 * getter & setter
+	 * Getter & setter
 	 */
 	public function getId() { return $this->id; }		// read only
 	public function getUuid() { return $this->uuid; }	// read only
diff --git a/backend/lib/Model/Group.php b/backend/lib/Model/Group.php
index 9e64c93..17561d5 100644
--- a/backend/lib/Model/Group.php
+++ b/backend/lib/Model/Group.php
@@ -24,11 +24,8 @@
 namespace Volkszaehler\Model;
 
 use Volkszaehler\Interpreter;
-
 use Doctrine\ORM;
-
 use Doctrine\Common\Collections;
-
 use Doctrine\Common\Collections\ArrayCollection;
 
 /**
diff --git a/backend/lib/Util/ClassLoader.php b/backend/lib/Util/ClassLoader.php
index 2e61aaf..8d2f2ec 100644
--- a/backend/lib/Util/ClassLoader.php
+++ b/backend/lib/Util/ClassLoader.php
@@ -25,9 +25,9 @@
 namespace Volkszaehler\Util;
 
 /**
- * class loader for volkszaehler and vendor libraries
+ * Classloader for volkszaehler and vendor libraries
  *
- * namespace is mapped to the filesystem structure
+ * Namespace is mapped to the filesystem structure
  *
  * @package util
  * @author Roman Borschel <roman@code-factory.org>
diff --git a/backend/lib/Util/Configuration.php b/backend/lib/Util/Configuration.php
index 6b1a813..5db1cf1 100644
--- a/backend/lib/Util/Configuration.php
+++ b/backend/lib/Util/Configuration.php
@@ -24,7 +24,7 @@
 namespace Volkszaehler\Util;
 
 /**
- * static configuration class for loading and storing the configuration to the disk
+ * Static configuration class for loading and storing the configuration to the disk
  *
  * @package util
  * @author Steffen Vogel <info@steffenvogel.de>
diff --git a/backend/lib/Util/Debug.php b/backend/lib/Util/Debug.php
index 182ba43..7c0b219 100644
--- a/backend/lib/Util/Debug.php
+++ b/backend/lib/Util/Debug.php
@@ -26,7 +26,7 @@ namespace Volkszaehler\Util;
 use Doctrine\DBAL\Logging;
 
 /**
- * static debugging class
+ * Static debugging class
  *
  * @package util
  * @author Steffen Vogel <info@steffenvogel.de>
diff --git a/backend/lib/View/JSON.php b/backend/lib/View/JSON.php
index 26713db..5924d7b 100644
--- a/backend/lib/View/JSON.php
+++ b/backend/lib/View/JSON.php
@@ -30,12 +30,12 @@ use Volkszaehler\Model;
 /**
  * JSON view
  *
- * also used for data
- *
  * @package default
  * @author Steffen Vogel <info@steffenvogel.de>
  */
 class JSON extends View {
+	const PRECISSION = 5;
+
 	protected $json = array();
 
 	protected $padding = FALSE;
@@ -63,18 +63,21 @@ class JSON extends View {
 		$jsonChannel['unit'] = $channel->getUnit();
 		$jsonChannel['name'] = $channel->getName();
 		$jsonChannel['description'] = $channel->getDescription();
-		$jsonChannel['resolution'] = (int) $channel->getResolution();
-		$jsonChannel['cost'] = (float) $channel->getCost();
+
+		if ($channel->getType() == 'meter') {
+			$jsonChannel['resolution'] = (int) $channel->getResolution();
+			$jsonChannel['cost'] = (float) $channel->getCost();
+		}
 
 		if (isset($data)) {
-			$jsonChannel['data'] = $data;
+			$jsonChannel['data'] = self::convertData($data);
 		}
 
 		$this->json['channels'][] = $jsonChannel;
 	}
 
 	public function addGroup(Model\Group $group, $recursive = FALSE) {
-		$this->json['groups'][] = $this->toJson($group, $recursive);
+		$this->json['groups'][] = self::convertJson($group, $recursive);
 	}
 
 	public function addDebug(Util\Debug $debug) {
@@ -99,7 +102,7 @@ class JSON extends View {
 		);
 	}
 
-	protected function toJson(Model\Group $group, $recursive = FALSE) {
+	protected static function convertGroup(Model\Group $group, $recursive = FALSE) {
 		$jsonGroup = array();
 
 		$jsonGroup['uuid'] = (string) $group->getUuid();
@@ -122,6 +125,20 @@ class JSON extends View {
 		return $jsonGroup;
 	}
 
+	protected static function convertData($data) {
+		$jsonData = array();
+
+		foreach ($data as $reading) {
+			$jsonData[] = array(
+				(int) $reading[0],
+				(float) round($reading[1], JSON::PRECISSION),
+				(int) $reading[2]
+			);
+		}
+
+		return $jsonData;
+	}
+
 	public function renderResponse() {
 		$json = json_encode($this->json);
 
diff --git a/backend/lib/View/JpGraph.php b/backend/lib/View/JpGraph.php
index 0e5e28e..ffc88fc 100644
--- a/backend/lib/View/JpGraph.php
+++ b/backend/lib/View/JpGraph.php
@@ -31,9 +31,9 @@ require_once \Volkszaehler\BACKEND_DIR . '/lib/vendor/JpGraph/jpgraph_scatter.ph
 require_once \Volkszaehler\BACKEND_DIR . '/lib/vendor/JpGraph/jpgraph_date.php';
 
 /**
- * plotting and graphing of data on the server side
+ * Plotting and graphing of data on the server side
  *
- * this view uses the JpGraph PHP5 plotting library
+ * This view uses the JpGraph PHP5 plotting library
  *
  * @package default
  * @author Steffen Vogel <info@steffenvogel.de>
diff --git a/backend/lib/View/PlainText.php b/backend/lib/View/PlainText.php
index e67386d..f0800cd 100644
--- a/backend/lib/View/PlainText.php
+++ b/backend/lib/View/PlainText.php
@@ -28,7 +28,7 @@ use Volkszaehler\Util;
 use Volkszaehler\Model;
 
 /**
- * Plain Text view
+ * Plain text view
  *
  * @author Steffen Vogel <info@steffenvogel.de>
  * @package default
diff --git a/backend/lib/View/View.php b/backend/lib/View/View.php
index efe6e4e..6eeb7ac 100644
--- a/backend/lib/View/View.php
+++ b/backend/lib/View/View.php
@@ -40,7 +40,7 @@ interface ViewInterface {
 }
 
 /**
- * superclass for all view classes
+ * Superclass for all view classes
  *
  * @package default
  * @author Steffen Vogel <info@steffenvogel.de>
diff --git a/backend/volkszaehler.conf.default.php b/backend/volkszaehler.conf.default.php
index d9a2930..97d3fdc 100644
--- a/backend/volkszaehler.conf.default.php
+++ b/backend/volkszaehler.conf.default.php
@@ -1,8 +1,8 @@
 <?php
 /**
- * configuration template
+ * Configuration template
  *
- * you should use this file to obtain your custom configuration
+ * You should use this file to obtain your custom configuration
  * new parameters should be documented
  *
  * @copyright Copyright (c) 2010, The volkszaehler.org project