diff --git a/lib/Controller/DataController.php b/lib/Controller/DataController.php
index a973fe6..9a2e07b 100644
--- a/lib/Controller/DataController.php
+++ b/lib/Controller/DataController.php
@@ -40,8 +40,11 @@ class DataController extends Controller {
 	public function get(Model\Entity $entity) {
 		$from = $this->view->request->getParameter('from');
 		$to = $this->view->request->getParameter('to');
+		$tuples = $this->view->request->getParameter('tuples');
+		$groupBy = $this->view->request->getParameter('group');
+		$class = $entity->getDefinition()->getInterpreter();
 
-		return $entity->getInterpreter($this->em, $from, $to);
+		return new $class($entity, $this->em, $from, $to, $tuples, $groupBy);
 	}
 
 	/**
diff --git a/lib/Interpreter/Iterator/DataAggregationIterator.php b/lib/Interpreter/DataIterator.php
similarity index 55%
rename from lib/Interpreter/Iterator/DataAggregationIterator.php
rename to lib/Interpreter/DataIterator.php
index 6d161b1..dfd7382 100644
--- a/lib/Interpreter/Iterator/DataAggregationIterator.php
+++ b/lib/Interpreter/DataIterator.php
@@ -21,21 +21,25 @@
  * along with volkszaehler.org. If not, see <http://www.gnu.org/licenses/>.
  */
 
-namespace Volkszaehler\Interpreter\Iterator;
+namespace Volkszaehler\Interpreter;
 
 use Volkszaehler\Util;
-
 use Doctrine\DBAL;
 
 /**
  * @author Steffen Vogel <info@steffenvogel.de>
  * @package default
  */
-class DataAggregationIterator implements \Iterator, \Countable {
+class DataIterator implements \Iterator, \Countable {
+	protected $stmt;	// PDO statement
+
 	protected $current;	// the current data
 	protected $key;		// key
-	protected $size;	// total readings in PDOStatement
-	protected $iterator;	// subiterator
+	private $rowKey;	// internal key for PDO statement
+	
+	protected $rowCount;	// num of readings in PDOStatement
+	protected $tupleCount;	// num of requested tuples
+	protected $packageSize; // num of rows we aggregate in each tuple
 
 	/**
 	 * Constructor
@@ -44,28 +48,40 @@ class DataAggregationIterator implements \Iterator, \Countable {
 	 * @param integer $size
 	 * @param integer $tuples
 	 */
-	public function __construct(\PDOStatement $stmt, $rows, $count) {
-		$this->iterator = new DataIterator($stmt, $rows);
+	public function __construct(\PDOStatement $stmt, $rowCount, $tupleCount) {
+		$this->rowCount = $rowCount;
+		$this->tupleCount = $tupleCount;
+	
+		$this->stmt = $stmt;
+		$this->stmt->setFetchMode(\PDO::FETCH_NUM);
 
-		$this->packageSize = floor($rows / $count);
-		$this->size = $count;
+		if ($this->rowCount > $this->tupleCount) {
+			$this->packageSize = floor($this->rowCount / $this->tupleCount);
+			$this->tupleCount = floor($this->rowCount / $this->packageSize) + $this->rowCount % $this->packageSize;
+		}
+		else {
+			 $this->packageSize = 1;
+		}
 	}
 
 	/**
 	 * Aggregate data
 	 */
 	public function next() {
-		$this->current = array(0, 0, 0);
-		for ($i = 0; $i < $this->packageSize; $i++, $this->iterator->next()) {
-			$tuple = $this->iterator->current();
+		$package = array(0, 0, 0);
+		for ($i = 0; $i < $this->packageSize && $this->valid(); $i++) {
+			$tuple = $this->stmt->fetch();
 
-			$this->current[0] = $tuple[0];
-			$this->current[1] += $tuple[1];
-			$this->current[2] += $tuple[2];
+			$package[0] = $tuple[0];
+			$package[1] += $tuple[1];
+			$package[2] += $tuple[2];
+			
+			$this->rowKey++;
 		}
-
+		
 		$this->key++;
-		return $this->current;
+		Util\Debug::log('key++', $this->key);
+		return $this->current = $package;
 	}
 
 	/**
@@ -75,24 +91,18 @@ class DataAggregationIterator implements \Iterator, \Countable {
 	 * PDOStatement hasn't a rewind()
 	 */
 	public function rewind() {
-		$this->iterator->rewind();
-		// skip first readings to get an even divisor
-		$skip = count($this->iterator) - count($this) * $this->packageSize;
-		for ($i = 0; $i < $skip; $i++) {
-			$this->iterator->next();
-		}
-		return $this->next();
+		$this->key = $this->rowKey = 0;
 	}
 
 	public function valid() {
-		return $this->key <= $this->size;
+		return $this->rowKey < $this->rowCount;
 	}
 
 	/**
 	 * Getter & setter
 	 */
 	public function getPackageSize() { return $this->packageSize; }
-	public function count() { return $this->size; }
+	public function count() { return $this->tupleCount; }
 	public function key() { return $this->key; }
 	public function current() { return $this->current; }
 }
diff --git a/lib/Interpreter/Interpreter.php b/lib/Interpreter/Interpreter.php
index ca012d2..67b0534 100644
--- a/lib/Interpreter/Interpreter.php
+++ b/lib/Interpreter/Interpreter.php
@@ -43,6 +43,7 @@ abstract class Interpreter {
 
 	protected $from;
 	protected $to;
+	protected $groupBy;
 	
 	protected $rowCount = NULL;
 	protected $tupleCount = NULL;
@@ -55,14 +56,25 @@ abstract class Interpreter {
 	 * @param integer $from timestamp in ms since 1970
 	 * @param integer $to timestamp in ms since 1970
 	 */
-	public function __construct(Model\Channel $channel, ORM\EntityManager $em, $from, $to) {
+	public function __construct(Model\Channel $channel, ORM\EntityManager $em, $from, $to, $tupleCount, $groupBy) {
 		$this->channel = $channel;
+		$this->tupleCount = $tupleCount;
+		$this->groupBy = $groupBy;
 		
 		// get dbal connection from EntityManager
 		$this->conn = $em->getConnection();
 
-		$this->from = (isset($from)) ? self::parseDateTimeString($from, time() * 1000) : NULL;
-		$this->to = (isset($to)) ? self::parseDateTimeString($to, (isset($this->from)) ? $this->from : time() * 1000) : NULL;
+		$this->from = $from;
+		$this->to = $to;
+		
+		// parse interval
+		if (isset($from)) {
+			$this->from = self::parseDateTimeString($from, time() * 1000);
+		}
+		
+		if (isset($to)) {
+			$this->to = self::parseDateTimeString($to, (isset($this->from)) ? $this->from : time() * 1000);
+		}
 
 		if (isset($this->from) && isset($this->to) && $this->from > $this->to) {
 			throw new \Exception('&from is larger than &to parameter');
@@ -75,13 +87,13 @@ abstract class Interpreter {
 	 * @param string|integer $groupBy
 	 * @return Volkszaehler\DataIterator
 	 */
-	protected function getData($count = NULL, $groupBy = NULL) {
+	protected function getData() {
 		// prepare sql
 		$sql['from']	= ' FROM data';
 		$sql['where']	= ' WHERE channel_id = ?' . self::buildDateTimeFilterSQL($this->from, $this->to);
 		$sql['orderBy']	= ' ORDER BY timestamp ASC';
 
-		if ($groupBy && $sql['groupFields'] = self::buildGroupBySQL($groupBy)) {
+		if ($this->groupBy && $sql['groupFields'] = self::buildGroupBySQL($this->groupBy)) {
 			$sql['rowCount']	= 'SELECT COUNT(DISTINCT ' . $sql['groupFields'] . ')' . $sql['from'] . $sql['where'];
 			$sql['fields']		= ' MAX(timestamp) AS timestamp, SUM(value) AS value, COUNT(timestamp) AS count';
 			$sql['groupBy']		= ' GROUP BY ' . $sql['groupFields'];
@@ -98,15 +110,10 @@ abstract class Interpreter {
 		// query for data
 		$stmt = $this->conn->executeQuery('SELECT ' . $sql['fields'] . $sql['from'] . $sql['where'] . $sql['groupBy'] . $sql['orderBy'], array($this->channel->getId()));
 
-		// return iterators
-		if ($sql['groupBy'] || is_null($count) || $this->rowCount < $count) {
-			$this->tupleCount = $this->rowCount;
-			return new Iterator\DataIterator($stmt, $this->rowCount);
-		}
-		else {
-			$this->tupleCount = $count;
-			return new Iterator\DataAggregationIterator($stmt, $this->rowCount, $count);
-		}
+		Util\Debug::log('rowcount', $this->rowCount);
+		Util\Debug::log('tuplecount', $this->tupleCount);
+
+		return new DataIterator($stmt, $this->rowCount, $this->tupleCount);
 	}
 
 	/**
diff --git a/lib/Interpreter/Iterator/DataIterator.php b/lib/Interpreter/Iterator/DataIterator.php
deleted file mode 100644
index ad3f590..0000000
--- a/lib/Interpreter/Iterator/DataIterator.php
+++ /dev/null
@@ -1,100 +0,0 @@
-<?php
-/**
- * @package default
- * @copyright Copyright (c) 2010, The volkszaehler.org project
- * @license http://www.gnu.org/licenses/gpl.txt GNU Public License
- */
-/*
- * This file is part of volkzaehler.org
- *
- * volkzaehler.org is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * any later version.
- *
- * volkzaehler.org is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with volkszaehler.org. If not, see <http://www.gnu.org/licenses/>.
- */
-
-namespace Volkszaehler\Interpreter\Iterator;
-
-use Volkszaehler\Util;
-use Doctrine\DBAL;
-
-/**
- * @author Steffen Vogel <info@steffenvogel.de>
- * @package default
- */
-class DataIterator implements \Iterator, \Countable {
-	protected $current;	// the current data
-	protected $key;		// key
-	protected $stmt;	// PDOStatement
-	protected $size;	// total readings in PDOStatement
-
-	/**
-	 * Constructor
-	 *
-	 * @param \PDOStatement $stmt
-	 * @param integer $size
-	 */
-	public function __construct(\PDOStatement $stmt, $size) {
-		$this->size = $size;
-		$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++;
-		return $this->current = $this->stmt->fetch();
-	}
-
-	/**
-	 * @return integer the nth data row
-	 */
-	public function key() {
-		return $this->key;
-	}
-
-	/**
-	 * @return boolean do we have another row in the resultset?
-	 */
-	public function valid() {
-		return is_array($this->current);
-	}
-
-	/**
-	 * Rewind the iterator
-	 *
-	 * Should only be called once
-	 * PDOStatement hasn't a rewind() aquivalent
-	 */
-	public function rewind() {
-		$this->key = 0;
-		return $this->current = $this->stmt->fetch();
-	}
-
-	/**
-	 * Get total num of rows
-	 * @return integer
-	 */
-	public function count() {
-		return $this->size;
-	}
-}
-
-?>
diff --git a/lib/Interpreter/MeterInterpreter.php b/lib/Interpreter/MeterInterpreter.php
index c06ab8b..b544914 100644
--- a/lib/Interpreter/MeterInterpreter.php
+++ b/lib/Interpreter/MeterInterpreter.php
@@ -85,14 +85,15 @@ class MeterInterpreter extends Interpreter {
 	 * @todo untested
 	 * @return array with timestamp, values, and pulse count
 	 */
-	public function processData($count, $groupBy, $callback) {
-		$pulses = parent::getData($count, $groupBy);
+	public function processData($callback) {
+		$pulses = parent::getData();
 
 		$this->resolution = $this->channel->getProperty('resolution');
 		$this->pulseCount = 0;
 
 		$tuples = array();
-		$last = $pulses->rewind();
+		$pulses->rewind();
+		$last = $pulses->next();
 		$next = $pulses->next();
 		
 		while ($pulses->valid()) {
diff --git a/lib/Model/Entity.php b/lib/Model/Entity.php
index b6ac43b..6b37704 100644
--- a/lib/Model/Entity.php
+++ b/lib/Model/Entity.php
@@ -185,19 +185,6 @@ abstract class Entity {
 	public function getUuid() { return $this->uuid; }	// read only
 	public function getType() { return $this->type; }	// read only
 	public function getDefinition() { return Definition\EntityDefinition::get($this->type); }
-
-	/**
-	 * Get 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) {
-		$class = $this->getDefinition()->getInterpreter();
-		return new $class($this, $em, $from, $to);
-	}
 }
 
 ?>
diff --git a/lib/View/JSON.php b/lib/View/JSON.php
index 1b03a42..5ac087c 100644
--- a/lib/View/JSON.php
+++ b/lib/View/JSON.php
@@ -202,8 +202,6 @@ class JSON extends View {
 		$this->json['data']['uuid'] = $interpreter->getEntity()->getUuid();
 
 		$data = $interpreter->processData(
-			$this->request->getParameter('tuples'),
-			$this->request->getParameter('group'), 
 			function($tuple) {
 				return array(
 					$tuple[0],