diff --git a/common/class.Collection.php b/common/class.Collection.php
index 70706afeb..917f97718 100644
--- a/common/class.Collection.php
+++ b/common/class.Collection.php
@@ -347,4 +347,4 @@ public function toArray()
         return (array) $returnValue;
     }
 
-}
\ No newline at end of file
+}
diff --git a/common/class.Utils.php b/common/class.Utils.php
index e357fa9b9..5907cfe27 100644
--- a/common/class.Utils.php
+++ b/common/class.Utils.php
@@ -1,7 +1,4 @@
 <?php
-use oat\oatbox\PhpSerializable;
-use oat\oatbox\service\ServiceManager;
-use oat\generis\model\kernel\uri\UriProvider;
 /**
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -22,6 +19,9 @@
  *               2009-2012 (update and modification) Public Research Centre Henri Tudor (under the project TAO-SUSTAIN & TAO-DEV);
  *
  */
+use oat\oatbox\PhpSerializable;
+use oat\oatbox\service\ServiceManager;
+use oat\generis\model\kernel\uri\UriProvider;
 
 /**
  *
diff --git a/common/persistence/class.Persistence.php b/common/persistence/class.Persistence.php
index e888c4943..1d5c333ee 100755
--- a/common/persistence/class.Persistence.php
+++ b/common/persistence/class.Persistence.php
@@ -21,6 +21,7 @@
  * @package generis
  *
  */
+
 abstract class common_persistence_Persistence
 {
     /**
@@ -102,15 +103,5 @@ protected function getParams(){
     protected function setParams($params){
         $this->params = $params;
     }
-
-    /**
-     * Generates a unique, not auto-increment based, primary key.
-     *
-     * @return string
-     */
-    public function getUniquePrimaryKey()
-    {
-        return strrev(uniqid('', true));
-    }
 }
 
diff --git a/common/persistence/sql/SetupDb.php b/common/persistence/sql/SetupDb.php
index 626cd6c9d..ac77b368e 100644
--- a/common/persistence/sql/SetupDb.php
+++ b/common/persistence/sql/SetupDb.php
@@ -20,16 +20,19 @@
  * @license GPLv2
  * @package tao
  */
+
 namespace oat\generis\persistence\sql;
 
 use Doctrine\DBAL\Schema\AbstractSchemaManager;
 use oat\oatbox\log\LoggerAwareTrait;
+use oat\oatbox\service\ConfigurableService;
 use Psr\Log\LoggerAwareInterface;
 use Doctrine\DBAL\Schema\Schema;
 use oat\generis\model\kernel\persistence\smoothsql\install\SmoothRdsModel;
 use Doctrine\DBAL\Exception\ConnectionException;
+use common_persistence_SqlPersistence as Persistence;
 
-class SetupDb implements LoggerAwareInterface
+class SetupDb extends ConfigurableService implements LoggerAwareInterface
 {
     use LoggerAwareTrait;
 
@@ -38,7 +41,7 @@ class SetupDb implements LoggerAwareInterface
      * @param \common_persistence_SqlPersistence $p
      * @throws \common_exception_InconsistentData
      */
-    public function setupDatabase(\common_persistence_SqlPersistence $p)
+    public function setupDatabase(Persistence $p)
     {
         $dbalDriver = $p->getDriver();
         if (!$dbalDriver instanceof \common_persistence_sql_dbal_Driver) {
@@ -50,10 +53,7 @@ public function setupDatabase(\common_persistence_SqlPersistence $p)
         $this->setupTables($p);
     }
 
-    /**
-     * @author "Lionel Lecaque, <lionel@taotesting.com>"
-     */
-    private function verifyDatabase(\common_persistence_SqlPersistence $p, $dbName)
+    private function verifyDatabase(Persistence $p, $dbName)
     {
         $schemaManager = $p->getSchemaManager()->getDbalSchemaManager();
         if (!$this->dbExists($schemaManager, $dbName)) {
@@ -61,10 +61,7 @@ private function verifyDatabase(\common_persistence_SqlPersistence $p, $dbName)
         }
     }
 
-    /**
-     * @author "Lionel Lecaque, <lionel@taotesting.com>"
-     */
-    private function setupTables(\common_persistence_SqlPersistence $p)
+    private function setupTables(Persistence $p)
     {
         $queries = $p->getPlatForm()->schemaToSql($this->getSchema($p));
         foreach ($queries as $query){
@@ -76,10 +73,11 @@ private function setupTables(\common_persistence_SqlPersistence $p)
      * Generate databse schema
      * @return Schema
      */
-    public function getSchema(\common_persistence_SqlPersistence $p)
+    public function getSchema(Persistence $p)
     {
         $schema = $p->getSchemaManager()->createSchema();
-        SmoothRdsModel::addSmoothTables($schema);
+        $smoothRdsModel = $this->getServiceLocator()->get(SmoothRdsModel::class); 
+        $smoothRdsModel->addSmoothTables($schema);
         $this->addKeyValueStoreTable($schema);
         return $schema;
     }
@@ -99,8 +97,9 @@ protected function addKeyValueStoreTable(Schema $schema)
     }
 
     /**
-     * @author "Lionel Lecaque, <lionel@taotesting.com>"
+     * @param AbstractSchemaManager $schemaManager
      * @param string $dbName
+     * @return bool
      */
     private function dbExists(AbstractSchemaManager $schemaManager, $dbName)
     {
@@ -112,10 +111,7 @@ private function dbExists(AbstractSchemaManager $schemaManager, $dbName)
         }
     }
 
-    /**
-     * @author "Lionel Lecaque, <lionel@taotesting.com>"
-     */
-    private function cleanDb(\common_persistence_SqlPersistence $p)
+    private function cleanDb(Persistence $p)
     {
         $schema = $p->getSchemaManager()->createSchema();
         $queries = $p->getPlatForm()->toDropSql($schema);
diff --git a/composer.json b/composer.json
index fb675162a..3c6b8f336 100755
--- a/composer.json
+++ b/composer.json
@@ -63,11 +63,12 @@
     "oat-sa/oatbox-extension-installer": "~1.1||dev-master",
     "php": "^7.1",
     "psr/log": "~1.0",
-    "oat-sa/lib-generis-search": "^2.0.1",
+    "oat-sa/lib-generis-search": "^2.1.0",
     "monolog/monolog": "^1.23.0",
     "fluent/logger": "^1.0.1",
     "symfony/lock": "^3.4",
-    "psr/container": "^1.0.0"
+    "psr/container": "^1.0.0",
+    "ramsey/uuid": "3.8.0"
   },
   "require-dev": {
     "mikey179/vfsstream": "1.4.0",
diff --git a/core/kernel/api/NewSqlModelFactory.php b/core/kernel/api/NewSqlModelFactory.php
new file mode 100644
index 000000000..680525e71
--- /dev/null
+++ b/core/kernel/api/NewSqlModelFactory.php
@@ -0,0 +1,119 @@
+<?php
+/**
+ * This program 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; under version 2
+ * of the License (non-upgradable).
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ * Copyright (c) 2019 (original work) Open Assessment Technologies SA
+ */
+
+namespace oat\generis\model\kernel\api;
+
+use core_kernel_api_ModelFactory as ModelFactory;
+use Doctrine\DBAL\Schema\Schema;
+use oat\generis\Helper\UuidPrimaryKeyTrait;
+use RuntimeException;
+
+class NewSqlModelFactory extends ModelFactory
+{
+    use UuidPrimaryKeyTrait;
+
+    /**
+     * @inheritdoc
+     */
+    public function addNewModel($namespace)
+    {
+        $modelId = md5($namespace);
+
+        if ($this->getPersistence()->insert('models', ['modelid' => $modelId, 'modeluri' => $namespace]) === 0) {
+            throw new RuntimeException('A problem occurred while creating a new model.');
+        }
+        return $modelId;
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function prepareStatement($modelId, $subject, $predicate, $object, $lang, $author)
+    {
+        $date = $this->getPersistence()->getPlatForm()->getNowExpression();
+
+        return [
+            'id' => $this->getUniquePrimaryKey(),
+            'modelid' => $modelId,
+            'subject' => $subject,
+            'predicate' => $predicate,
+            'object' => $object,
+            'l_language' => $lang,
+            'author' => $author ?? '',
+            'epoch' => $date,
+        ];
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function buildModelSqlCondition(array $models)
+    {
+        $models = array_map(
+            function ($a) {
+                return "'" . $a . "'";
+            },
+            $models
+        );
+        return parent::buildModelSqlCondition($models);
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function getPropertySortingField()
+    {
+        return 'epoch';
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function createModelsTable(Schema $schema)
+    {
+        $table = $schema->createTable('models');
+        $table->addColumn('modelid', 'string', ['length' => 36, 'notnull' => true]);
+        $table->addColumn('modeluri', 'string', ['length' => 255]);
+        $table->setPrimaryKey(['modelid']);
+
+        return $table;
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function createStatementsTable(Schema $schema)
+    {
+        $table = $schema->createTable('statements');
+        $table->addColumn('id', 'string', ['length' => 36, 'notnull' => true]);
+        $table->addColumn('modelid', 'string', ['length' => 23, 'notnull' => true]);
+        $table->addColumn('subject', 'string', ['length' => 255]);
+        $table->addColumn('predicate', 'string', ['length' => 255]);
+        $table->addColumn('object', 'text', []);
+        $table->addColumn('l_language', 'string', ['length' => 255]);
+        $table->addColumn('author', 'string', ['length' => 255]);
+        $table->addColumn('epoch', 'string', ['notnull' => true]);
+
+        $table->setPrimaryKey(['id']);
+        $table->addIndex(['subject', 'predicate'], 'k_sp');
+        $table->addIndex(['predicate', 'object'], 'k_po');
+
+        return $table;
+    }
+}
diff --git a/core/kernel/api/RdsModelFactory.php b/core/kernel/api/RdsModelFactory.php
new file mode 100644
index 000000000..aea184593
--- /dev/null
+++ b/core/kernel/api/RdsModelFactory.php
@@ -0,0 +1,108 @@
+<?php
+
+/**
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; under version 2
+ * of the License (non-upgradable).
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ * Copyright (c) 2019 (original work) Open Assessment Technologies SA
+ */
+
+namespace oat\generis\model\kernel\api;
+
+use core_kernel_api_ModelFactory as ModelFactory;
+use Doctrine\DBAL\Schema\Schema;
+use RuntimeException;
+
+class RdsModelFactory extends ModelFactory
+{
+    /**
+     * @inheritdoc
+     */
+    public function addNewModel($namespace)
+    {
+        $persistence = $this->getPersistence();
+        if ($persistence->insert('models', ['modeluri' => $namespace]) === 0) {
+            throw new RuntimeException('A problem occurred while creating a new model.');
+        }
+        
+        // Retrieving the inserted modelid (auto-increment).
+        $result = $persistence->query('select modelid from models where modeluri = ?', [$namespace]);
+        $modelId = $result->fetch();
+        return $modelId['modelid'];
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function prepareStatement($modelId, $subject, $predicate, $object, $lang, $author)
+    {
+        $date = $this->getPersistence()->getPlatForm()->getNowExpression();
+
+        return [
+            'modelid' => $modelId,
+            'subject' => $subject,
+            'predicate' => $predicate,
+            'object' => $object,
+            'l_language' => $lang,
+            'author' => $author ?? '',
+            'epoch' => $date,
+        ];
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function getPropertySortingField()
+    {
+        return 'id';
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function createModelsTable(Schema $schema)
+    {
+        // Models table.
+        $table = $schema->createTable('models');
+        $table->addColumn('modelid', 'integer', ['notnull' => true, 'autoincrement' => true]);
+        $table->addColumn('modeluri', 'string', ['length' => 255, 'default' => null]);
+        $table->setPrimaryKey(['modelid']);
+        $table->addOption('engine', 'MyISAM');
+
+        return $table;
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function createStatementsTable(Schema $schema)
+    {
+        $table = $schema->createTable('statements');
+        $table->addColumn('id', 'integer', ['notnull' => true, 'autoincrement' => true]);
+        $table->addColumn('modelid', 'integer', ['notnull' => true, 'default' => 0]);
+        $table->addColumn('subject', 'string', ['length' => 255, 'default' => null]);
+        $table->addColumn('predicate', 'string', ['length' => 255, 'default' => null]);
+        $table->addColumn('object', 'text', ['default' => null, 'notnull' => false]);
+        $table->addColumn('l_language', 'string', ['length' => 255, 'default' => null, 'notnull' => false]);
+        $table->addColumn('author', 'string', ['length' => 255, 'default' => null, 'notnull' => false]);
+        $table->addColumn('epoch', 'string', ['notnull' => null]);
+
+        $table->setPrimaryKey(['id']);
+        $table->addIndex(['subject', 'predicate'], 'k_sp', [], ['lengths' => [164, 164]]);
+        $table->addIndex(['predicate', 'object'], 'k_po', [], ['lengths' => [164, 164]]);
+        $table->addOption('engine', 'MyISAM');
+
+        return $table;
+    }
+}
diff --git a/core/kernel/api/class.ModelFactory.php b/core/kernel/api/class.ModelFactory.php
index c47d2dd0d..351b5d583 100644
--- a/core/kernel/api/class.ModelFactory.php
+++ b/core/kernel/api/class.ModelFactory.php
@@ -16,112 +16,193 @@
  *
  * Copyright (c) 2013 (original work) Open Assessment Technologies SA (under the project TAO-PRODUCT);
  *
- * @author "Lionel Lecaque, <lionel@taotesting.com>"
+ * @author  "Lionel Lecaque, <lionel@taotesting.com>"
  * @license GPLv2
  * @package generis
- 
  *
  */
-class core_kernel_api_ModelFactory{
-    
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\DBAL\Schema\Table;
+use common_persistence_SqlPersistence as Persistence;
+use oat\generis\persistence\PersistenceManager;
+use oat\oatbox\log\LoggerAwareTrait;
+use oat\oatbox\service\ConfigurableService;
+
+abstract class core_kernel_api_ModelFactory extends ConfigurableService
+{
+    use LoggerAwareTrait;
     
+    const SERVICE_ID = __CLASS__;
+    const OPTION_PERSISTENCE = 'persistence';
+    const DEFAULT_AUTHOR = 'http://www.tao.lu/Ontologies/TAO.rdf#installator';
+
     /**
      * @author "Lionel Lecaque, <lionel@taotesting.com>"
      * @param string $namespace
      * @return string
      */
-    private function getModelId($namespace){
-        $dbWrapper = core_kernel_classes_DbWrapper::singleton();
-        
+    public function getModelId($namespace)
+    {
+        if (substr($namespace, -1) !== '#') {
+            $namespace .= '#';
+        }
+
         $query = 'SELECT modelid FROM models WHERE (modeluri = ?)';
-        $results = $dbWrapper->query($query, array($namespace));
-       
-        return $results->fetchColumn(0);
+        $results = $this->getPersistence()->query($query, [$namespace]);
 
+        return $results->fetchColumn(0);
     }
-    
+
     /**
-     * @author "Lionel Lecaque, <lionel@taotesting.com>"
+     * Creates a new model in the ontology.
+     *
      * @param string $namespace
+     *
+     * @return string|int new added model id
+     * @throws RuntimeException when a problem occurs when creating the new model in db.
      */
-    private function addNewModel($namespace){
-        $dbWrapper = core_kernel_classes_DbWrapper::singleton();
-        $results = $dbWrapper->insert('models', array('modeluri' =>$namespace));
-        
-        
-    }
-    
+    abstract public function addNewModel($namespace);
+
     /**
-     * @author "Lionel Lecaque, <lionel@taotesting.com>"
+     * Creates a new model.
      * @param string $namespace
      * @param string $data xml content
+     * @return bool Were triples added?
      */
-    public function createModel($namespace, $data){
-
+    public function createModel($namespace, $data)
+    {
         $modelId = $this->getModelId($namespace);
-        if($modelId === false){
-            common_Logger::d('modelId not found, need to add namespace '. $namespace);
-            $this->addNewModel($namespace);
-            //TODO bad way, need to find better
-            $modelId = $this->getModelId($namespace);
+        if ($modelId === false) {
+            $this->logInfo('modelId not found, need to add namespace ' . $namespace);
+            $modelId = $this->addNewModel($namespace);
         }
         $modelDefinition = new EasyRdf_Graph($namespace);
-        if(is_file($data)){
+        if (is_file($data)) {
             $modelDefinition->parseFile($data);
-        }else {
+        } else {
             $modelDefinition->parse($data);
         }
-        $graph = $modelDefinition->toRdfPhp();
-        $resources = $modelDefinition->resources();
         $format = EasyRdf_Format::getFormat('php');
-        
+
         $data = $modelDefinition->serialise($format);
-        
-        foreach ($data as $subjectUri => $propertiesValues){
-            foreach ($propertiesValues as $prop=>$values){
-                foreach ($values as $k => $v) {
-                    $this->addStatement($modelId, $subjectUri, $prop, $v['value'], isset($v['lang']) ? $v['lang'] : null);
+
+        $returnValue = false;
+
+        foreach ($data as $subjectUri => $propertiesValues) {
+            foreach ($propertiesValues as $prop => $values) {
+                foreach ($values as $v) {
+                    $returnValue |= $this->addStatement($modelId, $subjectUri, $prop, $v['value'], isset($v['lang']) ? $v['lang'] : null);
                 }
             }
         }
-        
-        return true;
+
+        return $returnValue;
     }
-    
+
     /**
-     * Adds a statement to the ontology if it does not exist yet
-     * 
-     * @author "Joel Bout, <joel@taotesting.com>"
-     * @param int $modelId
-     * @param string $subject
-     * @param string $predicate
-     * @param string $object
-     * @param string $lang
+     * Adds a statement to the ontology if it does not exist yet.
+     * @param string|int $modelId
+     * @param string     $subject
+     * @param string     $predicate
+     * @param string     $object
+     * @param string     $lang
+     * @param string     $author
+     * @return bool Was a row added?
      */
-    private function addStatement($modelId, $subject, $predicate, $object, $lang = null) {
-        $result = core_kernel_classes_DbWrapper::singleton()->query(
+    public function addStatement($modelId, $subject, $predicate, $object, $lang = null, $author = self::DEFAULT_AUTHOR)
+    {
+        // Casting values and types.
+        $object = (string)$object;
+        if (is_null($lang)) {
+            $lang = '';
+        }
+
+        // TODO: refactor this to use a triple store abstraction.
+        $result = $this->getPersistence()->query(
             'SELECT count(*) FROM statements WHERE modelid = ? AND subject = ? AND predicate = ? AND object = ? AND l_language = ?',
-            array($modelId, $subject, $predicate, $object, (is_null($lang)) ? '' : $lang)
+            [$modelId, $subject, $predicate, $object, $lang]
         );
-        
-        if (intval($result->fetchColumn()) === 0) {
-            $dbWrapper = core_kernel_classes_DbWrapper::singleton();
-            $date = $dbWrapper->getPlatForm()->getNowExpression();
-
-            $dbWrapper->insert(
-                'statements',
-                array(
-                    'modelid' =>  $modelId,
-                    'subject' =>$subject,
-                    'predicate'=> $predicate,
-                    'object' => $object,
-                    'l_language' => is_null($lang) ? '' : $lang,
-                    'author' => 'http://www.tao.lu/Ontologies/TAO.rdf#installator',
-                    'epoch' => $date
-                )
-            );
+
+        if ((int)$result->fetchColumn() > 0) {
+            return false;
         }
+
+        return (bool)$this->getPersistence()->insert(
+            'statements',
+            $this->prepareStatement($modelId, $subject, $predicate, $object, $lang, is_null($author) ? '' : $author)
+        );
     }
-    
 
-}
\ No newline at end of file
+    /**
+     * Prepares a statement to be inserted in the ontology.
+     * @param string|int $modelId
+     * @param string     $subject
+     * @param string     $predicate
+     * @param string     $object
+     * @param string     $lang
+     * @param string     $author
+     * @return array
+     */
+    abstract public function prepareStatement($modelId, $subject, $predicate, $object, $lang, $author);
+
+    /**
+     * Creates a query for iterator on selected statements.
+     * @param $modelIds
+     * @return string
+     */
+    public function getIteratorQuery($modelIds)
+    {
+        $where = '';
+        if ($modelIds !== null) {
+            $where = 'WHERE ' . $this->buildModelSqlCondition($modelIds);
+        }
+        return sprintf('SELECT * FROM statements %s ORDER BY %s', $where, $this->getPropertySortingField());
+    }
+
+    /**
+     * Prepares parameters for statement selection.
+     * @param array $models
+     *
+     * @return string
+     */
+    public function buildModelSqlCondition(array $models)
+    {
+        return 'modelid IN (' . implode(',', $models) . ')';
+    }
+
+    /**
+     * Returns the property to sort the statements on.
+     * @return string
+     */
+    abstract public function getPropertySortingField();
+
+    /**
+     * Creates table schema for models.
+     *
+     * @param Schema $schema
+     *
+     * @return Table
+     */
+    abstract public function createModelsTable(Schema $schema);
+
+    /**
+     * Creates table schema for statements.
+     *
+     * @param Schema $schema
+     *
+     * @return Table
+     */
+    abstract public function createStatementsTable(Schema $schema);
+
+    /**
+     * @return Persistence
+     */
+    public function getPersistence()
+    {
+        $persistenceId = $this->hasOption(self::OPTION_PERSISTENCE) ?
+            $this->getOption(self::OPTION_PERSISTENCE)
+            : 'default';
+        return $this->getServiceLocator()->get(PersistenceManager::SERVICE_ID)->getPersistenceById($persistenceId);
+    }
+}
diff --git a/core/kernel/impl/class.ApiModelOO.php b/core/kernel/impl/class.ApiModelOO.php
index 21996e8e8..57a16f5f3 100644
--- a/core/kernel/impl/class.ApiModelOO.php
+++ b/core/kernel/impl/class.ApiModelOO.php
@@ -1,548 +1,479 @@
-<?php
-/*  
- * This program 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; under version 2
- * of the License (non-upgradable).
- * 
- * This program 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 this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
- * 
- * Copyright (c) 2002-2008 (original work) Public Research Centre Henri Tudor & University of Luxembourg (under the project TAO & TAO2);
- *               2008-2010 (update and modification) Deutsche Institut für Internationale Pädagogische Forschung (under the project TAO-TRANSFER);
- *               2009-2012 (update and modification) Public Research Centre Henri Tudor (under the project TAO-SUSTAIN & TAO-DEV);
- *               2017 (update and modification) Open Assessment Technologies SA (under the project TAO-PRODUCT);
- */
-?>
-<?php
-
-use oat\generis\model\OntologyRdf;
-use oat\generis\model\OntologyRdfs;
-use Doctrine\DBAL\DBALException;
-
-error_reporting(E_ALL);
-
-/**
- * Generis Object Oriented API - core\kernel\impl\class.ApiModelOO.php
- *
- * Short description of class core_kernel_impl_ApiModelOO
- *
- * This file is part of Generis Object Oriented API.
- *
- * Automatically generated on 29.03.2010, 15:28:05 with ArgoUML PHP module 
- * (last revised $Date: 2008-04-19 08:22:08 +0200 (Sat, 19 Apr 2008) $)
- *
- * @access public
- * @author firstname and lastname of author, <author@example.org>
- * @package generis
- 
- */
-class core_kernel_impl_ApiModelOO
-    extends core_kernel_impl_Api
-        implements core_kernel_api_ApiModel
-{
-    // --- ASSOCIATIONS ---
-
-
-    // --- ATTRIBUTES ---
-
-    /**
-     * Short description of attribute instance
-     *
-     * @access private
-     * @var ApiModelOO
-     */
-    private static $instance = null;
-
-    // --- OPERATIONS ---
-
-
-    /**
-     * build xml rdf containing rdf:Description of all meta-data the conected
-     * may get
-     *
-     * @deprecated
-     * @access public
-     * @author firstname and lastname of author, <author@example.org>
-     * @param  array sourceNamespaces
-     * @return string
-     */
-    public function exportXmlRdf($sourceNamespaces = array())
-    {
-        $modelIds = array();
-    	foreach($sourceNamespaces as $namespace){
-			if(!preg_match("/\#$/", $namespace)){
-				$namespace .= "#";
-			}
-
-			$result = $dbWrapper->query('SELECT * FROM "models"  WHERE "modeluri" = ?', array(
-				$namespace
-			));
-			if ($row = $result->fetch(PDO::FETCH_ASSOC)){
-			    $modelIds[] = $row['modelid'];
-				$result->closeCursor();
-			}
-		}
-		return $xml = core_kernel_api_ModelExporter::exportXmlRdf($modelIds);
-       
-    }
-
-    /**
-     * import xml rdf files into the knowledge base
-     *
-     * @access public
-     * @author firstname and lastname of author, <author@example.org>
-     * @param  string targetNameSpace
-     * @param  string fileLocation
-     * @return boolean
-     */
-    public function importXmlRdf($targetNameSpace, $fileLocation)
-    {
-        $returnValue = (bool) false;
-
-        if(!file_exists($fileLocation) || !is_readable($fileLocation)){
-            throw new common_Exception("Unable to load ontology : $fileLocation");
-        }
-        
-	    if(!preg_match("/#$/", $targetNameSpace)){
-			$targetNameSpace .= '#';
-		}
-		$modFactory = new core_kernel_api_ModelFactory();
-		$returnValue = $modFactory->createModel($targetNameSpace, file_get_contents($fileLocation));
-		
-
-
-        return (bool) $returnValue;
-    }
-
-
-
-    /**
-     * returns an xml rdf serialization for uriResource with all meta dat found
-     * inferenced from te knowlege base about this resource
-     *
-     * @access public
-     * @author firstname and lastname of author, <author@example.org>
-     * @param  string uriResource
-     * @return string
-     */
-    public function getResourceDescriptionXML($uriResource)
-    {
-        $returnValue = (string) '';
-
-        
-        
-        
-        
-    	$dbWrapper = core_kernel_classes_DbWrapper::singleton();
-		$subject = $dbWrapper->quote($uriResource);
-		
-		$baseNs = array(
-						'xmlns:rdf'		=> 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
-						'xmlns:rdfs'	=> 'http://www.w3.org/2000/01/rdf-schema#'
-					);
-		
-		$query = 'SELECT "models"."modelid", "models"."modeluri" FROM "models" INNER JOIN "statements" ON "statements"."modelid" = "models"."modelid"
-											WHERE "statements"."subject" = ' . $subject;
-		$query = $dbWrapper->limitStatement($query, 1);
-		$result = $dbWrapper->query($query);
-		if($row = $result->fetch()){
-			$modelId  = $row['modelid'];
-			$modelUri =  $row['modeluri'];
-			if(!preg_match("/#$/", $modelUri)){
-				$modelUri .= '#';
-			}
-			
-			$result->closeCursor();
-		}
-		$currentNs = array("xmlns:ns{$modelId}" => $modelUri);
-		$currentNs = array_merge($baseNs, $currentNs);
-		
-		
-		$allModels = array();
-		$result = $dbWrapper->query('SELECT * FROM "models"');
-		while($row = $result->fetch(PDO::FETCH_ASSOC)){
-			$allModels[] = $row;
-		}
-		
-		$allNs = array();
-		foreach($allModels as $i => $model){
-			if(!preg_match("/#$/", $model['modeluri'])){
-				$model['modeluri'] .= '#';
-			}
-			$allNs["xmlns:ns{$model['modelid']}"] = $model['modeluri'];
-		}
-		$allNs = array_merge($baseNs, $allNs);
-				
-		try{
-				
-			$dom = new DOMDocument();
-			$dom->formatOutput = true;
-			$root = $dom->createElement('rdf:RDF');
-				
-			foreach($currentNs as $namespaceId => $namespaceUri){
-				$root->setAttribute($namespaceId, $namespaceUri);
-			}
-			$dom->appendChild($root);
-					
-			$description = $dom->createElement('rdf:Description');
-			$description->setAttribute('rdf:about', $uriResource);
-			
-			$result = $dbWrapper->query('SELECT * FROM "statements" WHERE "subject" = ' . $subject);
-			while($row = $result->fetch()){
-				
-				$predicate 	= trim($row['predicate']);
-				$object 	= trim($row['object']);
-				$lang 		= trim($row['l_language']);
-				
-				$nodeName = null;
-				
-				foreach($allNs as $namespaceId => $namespaceUri){
-					if($namespaceId == 'xml:base') {
-                        continue;
-                    }
-					if(preg_match("/^".preg_quote($namespaceUri, '/')."/", $predicate)){
-						if(!array_key_exists($namespaceId, $currentNs)){
-							$currentNs[$namespaceId] = $namespaceUri;
-							$root->setAttribute($namespaceId, $namespaceUri);
-						}
-						$nodeName = str_replace('xmlns:', '', $namespaceId).':'.str_replace($namespaceUri, '', $predicate);
-						break;
-					}
-				}
-				
-				$resourceValue = false;
-				foreach($allNs as $namespaceId => $namespaceUri){
-					if( preg_match("/^".preg_quote($namespaceUri, '/')."/", $object) || 
-						preg_match("/^http\:\/\/(.*)\#[a-zA-Z1-9]*/", $object)){
-						$resourceValue = true;
-						break;
-					}
-				}
-				if(!is_null($nodeName)){
-					try{
-						$node = $dom->createElement($nodeName);
-						if(!empty($lang)){
-							$node->setAttribute('xml:lang', $lang);
-						}
-						
-						if($resourceValue){
-								$node->setAttribute('rdf:resource', $object);
-						}
-						else{
-							if(!empty($object) && !is_null($object)){
-								
-								/**
-								 * Replace the CDATA section inside XML fields by a replacement tag:
-								 * <![CDATA[ ]]> to <CDATA></CDATA>
-								 * @todo check if this behavior is the right
-								 */
-								$object = str_replace('<![CDATA[', '<CDATA>', $object);
-								$object = str_replace(']]>', '</CDATA>', $object);
-
-								$node->appendChild($dom->createCDATASection($object));
-							}
-						}
-						$description->appendChild($node);
-					}
-					catch(DOMException $de){
-						//print $de;
-					}
-				}
-			}
-			$root->appendChild($description);
-			$returnValue = $dom->saveXml();
-		}
-		catch(DomException $e){
-			print $e;
-		}
-        
-        
-        
-
-        return (string) $returnValue;
-    }
-
-    /**
-     * returns metaclasses tat are not subclasses of other metaclasses
-     *
-     * @access public
-     * @author patrick.plichart@tudor.lu
-     * @return core_kernel_classes_ContainerCollection
-     */
-    public function getMetaClasses()
-    {
-        $returnValue = null;
-
-        
-        $returnValue = new core_kernel_classes_ContainerCollection(new core_kernel_classes_Container(__METHOD__),__METHOD__);
-        
-        $classClass = new core_kernel_classes_Class(OntologyRdfs::RDFS_CLASS);
-        foreach($classClass->getSubClasses(true) as $uri => $subClass){
-        	$returnValue->add($subClass);
-        }
-		
-
-        return $returnValue;
-    }
-
-    /**
-     * returns classes that are not subclasses of other classes
-     *
-     * @access public
-     * @author patrick.plichart@tudor.lu
-     * @return core_kernel_classes_ContainerCollection
-     */
-    public function getRootClasses()
-    {
-        $returnValue = null;
-
-        
-    
-        $returnValue = new core_kernel_classes_ContainerCollection(new core_kernel_classes_Container(__METHOD__),__METHOD__);
-        
-        $dbWrapper = core_kernel_classes_DbWrapper::singleton();
-        
-        $query =  "SELECT DISTINCT subject FROM statements WHERE (predicate = ? AND object = ?) 
-        			AND subject NOT IN (SELECT subject FROM statements WHERE predicate = ?)";
-    	$result	= $dbWrapper->query($query, array(
-			OntologyRdf::RDF_TYPE,
-            OntologyRdfs::RDFS_CLASS,
-            OntologyRdfs::RDFS_SUBCLASSOF
-        ));
-        
-        while ($row = $result->fetch()) {
-       		$returnValue->add(new core_kernel_classes_Class($row['subject']));
-        }
-		
-        
-
-        return $returnValue;
-    }
-
-    /**
-     * add a new statment to the knowledge base
-     *
-     * @access public
-     * @author patrick.plichart@tudor.lu
-     * @param  string subject
-     * @param  string predicate
-     * @param  string object
-     * @param  string language
-     * @return boolean
-     */
-    public function setStatement($subject, $predicate, $object, $language)
-    {
-        $returnValue = (bool) false;
-
-        
-        $dbWrapper 	= core_kernel_classes_DbWrapper::singleton();
-        $platform   = $dbWrapper->getPlatForm();
-        $localNs 	= common_ext_NamespaceManager::singleton()->getLocalNamespace();
-        $mask		= 'yyy[admin,administrators,authors]';	//now it's the default right mode
-        $query = 'INSERT INTO statements (modelid,subject,predicate,object,l_language,author,epoch)
-        			VALUES  (?, ?, ?, ?, ?, ? , ?);';
-
-        try{
-	        $returnValue = $dbWrapper->exec($query, array(
-	       		$localNs->getModelId(),
-	       		$subject,
-	       		$predicate,
-	       		$object,
-	       		$language,
-	       		\common_session_SessionManager::getSession()->getUserUri(),
-	            $platform->getNowExpression()
-	             
-	        ));
-        }
-        catch (DBALException $e){
-	        if($e->getCode() !== '00000'){
-				throw new common_Exception ("Unable to setStatement (SPO) {$subject}, {$predicate}, {$object} : " . $e->getMessage());
-			}
-        }
-        
-        
-
-        return (bool) $returnValue;
-    }
-
-    /**
-     * Short description of method getAllClasses
-     *
-     * @access public
-     * @author firstname and lastname of author, <author@example.org>
-     * @return core_kernel_classes_ContainerCollection
-     */
-    public function getAllClasses()
-    {
-        $returnValue = null;
-
-        
-    	
-        $returnValue = new core_kernel_classes_ContainerCollection(new core_kernel_classes_Container(__METHOD__),__METHOD__);
-        
-        $dbWrapper = core_kernel_classes_DbWrapper::singleton();
-        
-        $query =  "SELECT DISTINCT subject FROM statements WHERE (predicate = ? AND object = ?) OR predicate = ?";
-    	$result	= $dbWrapper->query($query, array(
-			OntologyRdf::RDF_TYPE,
-            OntologyRdfs::RDFS_CLASS,
-            OntologyRdfs::RDFS_SUBCLASSOF
-        ));
-        
-        while ($row = $result->fetch()) {
-        	$returnValue->add(new core_kernel_classes_Class($row['subject']));
-        }
-		
-        
-
-        return $returnValue;
-    }
-
-    /**
-     * Short description of method getSubject
-     *
-     * @access public
-     * @author firstname and lastname of author, <author@example.org>
-     * @param  string predicate
-     * @param  string object
-     * @return core_kernel_classes_ContainerCollection
-     */
-    public function getSubject($predicate, $object)
-    {
-        $returnValue = null;
-
-        
-		
-		$sqlQuery = "SELECT subject FROM statements WHERE predicate = ? AND object= ? ";
-		$dbWrapper = core_kernel_classes_DbWrapper::singleton();
-		$sqlResult = $dbWrapper->query($sqlQuery, array (
-			$predicate,
-			$object
-		));
-		$returnValue = new core_kernel_classes_ContainerCollection(new common_Object(__METHOD__));
-		while ($row = $sqlResult->fetch()){
-			$container = new core_kernel_classes_Resource($row['subject'], __METHOD__);
-			$container->debug = __METHOD__ ;
-			$returnValue->add($container);
-		}
-
-        
-
-        return $returnValue;
-    }
-
-    /**
-     * Short description of method removeStatement
-     *
-     * @access public
-     * @author firstname and lastname of author, <author@example.org>
-     * @param  string subject
-     * @param  string predicate
-     * @param  string object
-     * @param  string language
-     * @return boolean
-     */
-    public function removeStatement($subject, $predicate, $object, $language)
-    {
-        $returnValue = (bool) false;
-
-        
-        $dbWrapper 	= core_kernel_classes_DbWrapper::singleton();
-    
-        $query = "DELETE FROM statements WHERE subject = ?
-        			AND predicate = ? AND object = ?
-        			AND (l_language = ? OR l_language = '')";
-
-        $returnValue = $dbWrapper->exec($query, array(
-       		$subject,
-       		$predicate,
-       		$object,
-       		$language
-        ));
-        
-        
-
-        return (bool) $returnValue;
-    }
-
-    /**
-     * Short description of method getObject
-     *
-     * @access public
-     * @author firstname and lastname of author, <author@example.org>
-     * @param  string subject
-     * @param  string predicate
-     * @return core_kernel_classes_ContainerCollection
-     */
-    public function getObject($subject, $predicate)
-    {
-        $returnValue = null;
-
-        
-    	$sqlQuery = "SELECT object FROM statements WHERE subject = ? AND predicate = ?";
-		$dbWrapper = core_kernel_classes_DbWrapper::singleton();
-		$sqlResult = $dbWrapper->query($sqlQuery, array (
-			$subject,
-			$predicate
-		));
-		$returnValue = new core_kernel_classes_ContainerCollection(new common_Object(__METHOD__));
-		while ($row = $sqlResult->fetch()){
-			
-			$value = $row['object'];
-			if(!common_Utils::isUri($value)) {
-				$container = new core_kernel_classes_Literal($value);
-			}
-			else{
-				$container = new core_kernel_classes_Resource($value);
-			}
-			$container->debug = __METHOD__ ;
-			$returnValue->add($container);
-		}
-        
-
-        return $returnValue;
-    }
-
-    /**
-     * Short description of method singleton
-     *
-     * @access public
-     * @author firstname and lastname of author, <author@example.org>
-     * @return core_kernel_impl_ApiModelOO
-     */
-    public static function singleton()
-    {
-        $returnValue = null;
-
-        
-		if (!isset(self::$instance)) {
-			$c = __CLASS__;
-			self::$instance = new $c();
-		}
-		$returnValue = self::$instance;
-        
-
-        return $returnValue;
-    }
-
-    /**
-     * Short description of method __construct
-     *
-     * @access private
-     * @author firstname and lastname of author, <author@example.org>
-     * @return void
-     */
-    private function __construct()
-    {
-        
-        
-    }
-
-}
\ No newline at end of file
+<?php
+/*  
+ * This program 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; under version 2
+ * of the License (non-upgradable).
+ * 
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ * Copyright (c) 2002-2008 (original work) Public Research Centre Henri Tudor & University of Luxembourg (under the project TAO & TAO2);
+ *               2008-2010 (update and modification) Deutsche Institut für Internationale Pädagogische Forschung (under the project TAO-TRANSFER);
+ *               2009-2012 (update and modification) Public Research Centre Henri Tudor (under the project TAO-SUSTAIN & TAO-DEV);
+ *               2017 (update and modification) Open Assessment Technologies SA (under the project TAO-PRODUCT);
+ */
+
+use core_kernel_api_ModelFactory as ModelFactory;
+use core_kernel_classes_DbWrapper as DbWrapper;
+use core_kernel_persistence_Exception as PersistenceException;
+use oat\generis\model\OntologyRdf;
+use oat\generis\model\OntologyRdfs;
+use oat\oatbox\log\LoggerAwareTrait;
+use oat\oatbox\service\ServiceManager;
+
+error_reporting(E_ALL);
+
+/**
+ * Generis Object Oriented API - core\kernel\impl\class.ApiModelOO.php
+ *
+ * Short description of class core_kernel_impl_ApiModelOO
+ *
+ * This file is part of Generis Object Oriented API.
+ *
+ * Automatically generated on 29.03.2010, 15:28:05 with ArgoUML PHP module 
+ * (last revised $Date: 2008-04-19 08:22:08 +0200 (Sat, 19 Apr 2008) $)
+ *
+ * @access public
+ * @author firstname and lastname of author, <author@example.org>
+ * @package generis
+ 
+ */
+class core_kernel_impl_ApiModelOO
+    extends core_kernel_impl_Api
+        implements core_kernel_api_ApiModel
+{
+    use LoggerAwareTrait;
+    
+    /**
+     * @var core_kernel_impl_ApiModelOO
+     */
+    private static $instance = null;
+
+    /** @var ModelFactory */
+    private $modelFactory;
+
+    /**
+     * @author firstname and lastname of author, <author@example.org>
+     * @return void
+     */
+    private function __construct()
+    {
+        $serviceManager = ServiceManager::getServiceManager();
+        $this->modelFactory = $serviceManager->get(ModelFactory::SERVICE_ID);
+    }
+
+    /**
+     * build xml rdf containing rdf:Description of all meta-data the conected
+     * may get
+     *
+     * @deprecated
+     * @access public
+     * @author firstname and lastname of author, <author@example.org>
+     * @param  array sourceNamespaces
+     * @return string
+     */
+    public function exportXmlRdf($sourceNamespaces = array())
+    {
+        $modelIds = array();
+    	foreach($sourceNamespaces as $namespace){
+			if(!preg_match("/\#$/", $namespace)){
+				$namespace .= "#";
+			}
+
+			$result = $this->getPersistence()->query('SELECT * FROM "models"  WHERE "modeluri" = ?', array(
+				$namespace
+			));
+			if ($row = $result->fetch(PDO::FETCH_ASSOC)){
+			    $modelIds[] = $row['modelid'];
+				$result->closeCursor();
+			}
+		}
+		return $xml = core_kernel_api_ModelExporter::exportXmlRdf($modelIds);
+       
+    }
+
+    /**
+     * import xml rdf files into the knowledge base
+     *
+     * @access public
+     * @author firstname and lastname of author, <author@example.org>
+     * @param  string targetNameSpace
+     * @param  string fileLocation
+     * @return boolean
+     */
+    public function importXmlRdf($targetNameSpace, $fileLocation)
+    {
+        if(!file_exists($fileLocation) || !is_readable($fileLocation)){
+            throw new common_Exception("Unable to load ontology : $fileLocation");
+        }
+        
+	    if(!preg_match("/#$/", $targetNameSpace)){
+			$targetNameSpace .= '#';
+		}
+
+        return $this->modelFactory->createModel($targetNameSpace, file_get_contents($fileLocation));
+    }
+
+
+
+    /**
+     * returns an xml rdf serialization for uriResource with all meta dat found
+     * inferenced from te knowlege base about this resource
+     *
+     * @access public
+     * @author firstname and lastname of author, <author@example.org>
+     * @param  string uriResource
+     * @return string
+     */
+    public function getResourceDescriptionXML($uriResource)
+    {
+        $returnValue = '';
+        
+    	$persistence = $this->getPersistence();
+		$subject = $persistence->quote($uriResource);
+		
+		$baseNs = array(
+						'xmlns:rdf'		=> 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
+						'xmlns:rdfs'	=> 'http://www.w3.org/2000/01/rdf-schema#'
+					);
+		
+		$query = 'SELECT "models"."modelid", "models"."modeluri" FROM "models" INNER JOIN "statements" ON "statements"."modelid" = "models"."modelid"
+											WHERE "statements"."subject" = ' . $subject;
+		$query = $persistence->limitStatement($query, 1);
+		$result = $persistence->query($query);
+		if($row = $result->fetch()){
+			$modelId  = $row['modelid'];
+			$modelUri =  $row['modeluri'];
+			if(!preg_match("/#$/", $modelUri)){
+				$modelUri .= '#';
+			}
+			
+			$result->closeCursor();
+		}
+		$currentNs = array("xmlns:ns{$modelId}" => $modelUri);
+		$currentNs = array_merge($baseNs, $currentNs);
+		
+		
+		$allModels = array();
+		$result = $persistence->query('SELECT * FROM "models"');
+		while($row = $result->fetch(PDO::FETCH_ASSOC)){
+			$allModels[] = $row;
+		}
+		
+		$allNs = array();
+		foreach($allModels as $i => $model){
+			if(!preg_match("/#$/", $model['modeluri'])){
+				$model['modeluri'] .= '#';
+			}
+			$allNs["xmlns:ns{$model['modelid']}"] = $model['modeluri'];
+		}
+		$allNs = array_merge($baseNs, $allNs);
+				
+		try{
+				
+			$dom = new DOMDocument();
+			$dom->formatOutput = true;
+			$root = $dom->createElement('rdf:RDF');
+				
+			foreach($currentNs as $namespaceId => $namespaceUri){
+				$root->setAttribute($namespaceId, $namespaceUri);
+			}
+			$dom->appendChild($root);
+					
+			$description = $dom->createElement('rdf:Description');
+			$description->setAttribute('rdf:about', $uriResource);
+			
+			$result = $persistence->query('SELECT * FROM "statements" WHERE "subject" = ' . $subject);
+			while($row = $result->fetch()){
+				
+				$predicate 	= trim($row['predicate']);
+				$object 	= trim($row['object']);
+				$lang 		= trim($row['l_language']);
+				
+				$nodeName = null;
+				
+				foreach($allNs as $namespaceId => $namespaceUri){
+					if($namespaceId == 'xml:base') {
+                        continue;
+                    }
+					if(preg_match("/^".preg_quote($namespaceUri, '/')."/", $predicate)){
+						if(!array_key_exists($namespaceId, $currentNs)){
+							$currentNs[$namespaceId] = $namespaceUri;
+							$root->setAttribute($namespaceId, $namespaceUri);
+						}
+						$nodeName = str_replace('xmlns:', '', $namespaceId).':'.str_replace($namespaceUri, '', $predicate);
+						break;
+					}
+				}
+				
+				$resourceValue = false;
+				foreach($allNs as $namespaceId => $namespaceUri){
+					if( preg_match("/^".preg_quote($namespaceUri, '/')."/", $object) || 
+						preg_match("/^http\:\/\/(.*)\#[a-zA-Z1-9]*/", $object)){
+						$resourceValue = true;
+						break;
+					}
+				}
+				if(!is_null($nodeName)){
+					try{
+						$node = $dom->createElement($nodeName);
+						if(!empty($lang)){
+							$node->setAttribute('xml:lang', $lang);
+						}
+						
+						if($resourceValue){
+								$node->setAttribute('rdf:resource', $object);
+						}
+						else{
+							if(!empty($object) && !is_null($object)){
+								
+								/**
+								 * Replace the CDATA section inside XML fields by a replacement tag:
+								 * <![CDATA[ ]]> to <CDATA></CDATA>
+								 * @todo check if this behavior is the right
+								 */
+								$object = str_replace('<![CDATA[', '<CDATA>', $object);
+								$object = str_replace(']]>', '</CDATA>', $object);
+
+								$node->appendChild($dom->createCDATASection($object));
+							}
+						}
+						$description->appendChild($node);
+					} catch(DOMException $de){
+                        $this->logError($de);
+					}
+				}
+			}
+			$root->appendChild($description);
+			$returnValue = $dom->saveXml();
+		} catch(DomException $e){
+			$this->logError($e);
+		}
+        
+        return $returnValue;
+    }
+
+    /**
+     * returns metaclasses tat are not subclasses of other metaclasses
+     *
+     * @access public
+     * @author patrick.plichart@tudor.lu
+     * @return core_kernel_classes_ContainerCollection
+     */
+    public function getMetaClasses()
+    {
+        $returnValue = new core_kernel_classes_ContainerCollection(new core_kernel_classes_Container(__METHOD__),__METHOD__);
+        
+        $classClass = new core_kernel_classes_Class(OntologyRdfs::RDFS_CLASS);
+        foreach($classClass->getSubClasses(true) as $uri => $subClass){
+        	$returnValue->add($subClass);
+        }
+
+        return $returnValue;
+    }
+
+    /**
+     * returns classes that are not subclasses of other classes
+     *
+     * @access public
+     * @author patrick.plichart@tudor.lu
+     * @return core_kernel_classes_ContainerCollection
+     */
+    public function getRootClasses()
+    {
+        $returnValue = new core_kernel_classes_ContainerCollection(new core_kernel_classes_Container(__METHOD__),__METHOD__);
+        
+        $query =  "SELECT DISTINCT subject FROM statements WHERE (predicate = ? AND object = ?) 
+        			AND subject NOT IN (SELECT subject FROM statements WHERE predicate = ?)";
+    	$result	= $this->getPersistence()->query($query, array(
+			OntologyRdf::RDF_TYPE,
+            OntologyRdfs::RDFS_CLASS,
+            OntologyRdfs::RDFS_SUBCLASSOF
+        ));
+        
+        while ($row = $result->fetch()) {
+       		$returnValue->add(new core_kernel_classes_Class($row['subject']));
+        }
+		
+        return $returnValue;
+    }
+
+    /**
+     * add a new statment to the knowledge base
+     *
+     * @access public
+     * @author patrick.plichart@tudor.lu
+     * @param  string subject
+     * @param  string predicate
+     * @param  string object
+     * @param  string language
+     * @return boolean
+     */
+    public function setStatement($subject, $predicate, $object, $language)
+    {
+        $localNsManager = common_ext_NamespaceManager::singleton();
+        $modelId = $localNsManager->getLocalNamespace()->getModelId();
+        $currentUser = common_session_SessionManager::getSession()->getUserUri();
+
+        return $this->modelFactory->addStatement(
+            $modelId,
+            $subject,
+            $predicate,
+            $object,
+            $language,
+            $currentUser
+        );
+    }
+
+    /**
+     * Short description of method getAllClasses
+     *
+     * @access public
+     * @author firstname and lastname of author, <author@example.org>
+     * @return core_kernel_classes_ContainerCollection
+     */
+    public function getAllClasses()
+    {
+        $returnValue = new core_kernel_classes_ContainerCollection(new core_kernel_classes_Container(__METHOD__),__METHOD__);
+        
+        $query =  "SELECT DISTINCT subject FROM statements WHERE (predicate = ? AND object = ?) OR predicate = ?";
+    	$result	= $this->getPersistence()->query($query, array(
+			OntologyRdf::RDF_TYPE,
+            OntologyRdfs::RDFS_CLASS,
+            OntologyRdfs::RDFS_SUBCLASSOF
+        ));
+        
+        while ($row = $result->fetch()) {
+        	$returnValue->add(new core_kernel_classes_Class($row['subject']));
+        }
+		
+        return $returnValue;
+    }
+
+    /**
+     * Short description of method getSubject
+     *
+     * @access public
+     * @author firstname and lastname of author, <author@example.org>
+     * @param  string predicate
+     * @param  string object
+     * @return core_kernel_classes_ContainerCollection
+     */
+    public function getSubject($predicate, $object)
+    {
+        $returnValue = new core_kernel_classes_ContainerCollection(new common_Object(__METHOD__));
+        
+        $query = "SELECT subject FROM statements WHERE predicate = ? AND object= ? ";
+        $sqlResult = $this->getPersistence()->query($query, array (
+			$predicate,
+			$object
+		));
+
+		while ($row = $sqlResult->fetch()){
+			$container = new core_kernel_classes_Resource($row['subject'], __METHOD__);
+			$container->debug = __METHOD__ ;
+			$returnValue->add($container);
+		}
+
+        return $returnValue;
+    }
+
+    /**
+     * Short description of method removeStatement
+     *
+     * @access public
+     * @author firstname and lastname of author, <author@example.org>
+     * @param  string subject
+     * @param  string predicate
+     * @param  string object
+     * @param  string language
+     * @return boolean
+     */
+    public function removeStatement($subject, $predicate, $object, $language)
+    {
+        $query = "DELETE FROM statements WHERE subject = ?
+        			AND predicate = ? AND object = ?
+        			AND (l_language = ? OR l_language = '')";
+
+        $returnValue = $this->getPersistence()->exec($query, array(
+       		$subject,
+       		$predicate,
+       		$object,
+       		$language
+        ));
+
+        return (bool) $returnValue;
+    }
+
+    /**
+     * Short description of method getObject
+     *
+     * @access public
+     * @author firstname and lastname of author, <author@example.org>
+     * @param  string subject
+     * @param  string predicate
+     * @return core_kernel_classes_ContainerCollection
+     */
+    public function getObject($subject, $predicate)
+    {
+        $returnValue = new core_kernel_classes_ContainerCollection(new common_Object(__METHOD__));
+        
+    	$sqlQuery = "SELECT object FROM statements WHERE subject = ? AND predicate = ?";
+		$sqlResult = $this->getPersistence()->query($sqlQuery, array (
+			$subject,
+			$predicate
+		));
+		
+		while ($row = $sqlResult->fetch()){
+			
+			$value = $row['object'];
+			if(!common_Utils::isUri($value)) {
+				$container = new core_kernel_classes_Literal($value);
+			}
+			else{
+				$container = new core_kernel_classes_Resource($value);
+			}
+			$container->debug = __METHOD__ ;
+			$returnValue->add($container);
+		}
+
+        return $returnValue;
+    }
+
+    /**
+     * Short description of method singleton
+     *
+     * @access public
+     * @author firstname and lastname of author, <author@example.org>
+     * @return core_kernel_impl_ApiModelOO
+     */
+    public static function singleton()
+    {
+        $returnValue = null;
+
+        if (!isset(self::$instance)) {
+            $c = __CLASS__;
+            self::$instance = new $c();
+        }
+        $returnValue = self::$instance;
+
+        return $returnValue;
+    }
+
+    /**
+     * @return DbWrapper
+     * @throws PersistenceException
+     */
+    public function getPersistence()
+    {
+        // @TODO: inject dbWrapper as a dependency.
+        return DbWrapper::singleton();
+    }
+}
diff --git a/core/kernel/persistence/smoothsql/class.Resource.php b/core/kernel/persistence/smoothsql/class.Resource.php
index 6e2c6695c..8ffc52cfe 100644
--- a/core/kernel/persistence/smoothsql/class.Resource.php
+++ b/core/kernel/persistence/smoothsql/class.Resource.php
@@ -20,6 +20,7 @@
  *               2017 (update and modification) Open Assessment Technologies SA (under the project TAO-PRODUCT);
  */
 
+use core_kernel_api_ModelFactory as ModelFactory;
 use oat\generis\model\OntologyRdf;
 use oat\oatbox\session\SessionService;
 use oat\oatbox\user\UserLanguageServiceInterface;
@@ -36,19 +37,39 @@
 class core_kernel_persistence_smoothsql_Resource
     implements core_kernel_persistence_ResourceInterface
 {
+    /** @var ModelFactory */
+    protected $modelFactory;
 
     /**
      * @var core_kernel_persistence_smoothsql_SmoothModel
      */
     private $model;
-    
+
+    /**
+     * core_kernel_persistence_smoothsql_Resource constructor.
+     *
+     * @param core_kernel_persistence_smoothsql_SmoothModel $model
+     */
     public function __construct(core_kernel_persistence_smoothsql_SmoothModel $model) {
         $this->model = $model;
     }
-    
+
+    /**
+     * @return core_kernel_persistence_smoothsql_SmoothModel
+     */
     protected function getModel() {
         return $this->model;
     }
+
+    /**
+     * @return ModelFactory
+     */
+    protected function getModelFactory() {
+        if ($this->modelFactory === null) {
+            $this->modelFactory = $this->getServiceLocator()->get(ModelFactory::SERVICE_ID);
+        }
+        return $this->modelFactory;
+    }
     
     /**
      * @return common_persistence_SqlPersistence
@@ -58,11 +79,11 @@ protected function getPersistence() {
     }
     
     protected function getModelReadSqlCondition() {
-        return 'modelid IN ('.implode(',', $this->model->getReadableModels()).')';
+        return $this->getModelFactory()->buildModelSqlCondition($this->model->getReadableModels());
     }
     
     protected function getModelWriteSqlCondition() {
-        return 'modelid IN ('.implode(',',$this->model->getWritableModels()).')';
+        return $this->getModelFactory()->buildModelSqlCondition($this->model->getWritableModels());
     }
     
     protected function getNewTripleModelId() {
@@ -83,7 +104,7 @@ public function getTypes( core_kernel_classes_Resource $resource)
     {
         $returnValue = array();
 
-        
+        // TODO: move sql query to implementation. 
 		$sqlQuery = 'SELECT object FROM statements WHERE subject = ? and predicate = ?';
         $sth = $this->getPersistence()->query($sqlQuery,array($resource->getUri(), OntologyRdf::RDF_TYPE));
 
@@ -101,10 +122,11 @@ public function getTypes( core_kernel_classes_Resource $resource)
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
-     * @param  Property property
+     * @param  core_kernel_classes_Resource resource
+     * @param  core_kernel_classes_Property property
      * @param  array options
      * @return array
+     * @throws core_kernel_persistence_Exception
      */
     public function getPropertyValues( core_kernel_classes_Resource $resource,  core_kernel_classes_Property $property, $options = array())
     {
@@ -118,7 +140,6 @@ public function getPropertyValues( core_kernel_classes_Resource $resource,  core
 		$platform = $this->getPersistence()->getPlatForm();
 		
     	// Define language if required
-		$lang = '';
 		$defaultLg = '';
 		if (isset($options['lg'])) {
 			$lang = $options['lg'];
@@ -127,7 +148,8 @@ public function getPropertyValues( core_kernel_classes_Resource $resource,  core
             $default = $this->getServiceLocator()->get(UserLanguageServiceInterface::SERVICE_ID)->getDefaultLanguage();
             $defaultLg = ' OR l_language = ' . $this->getPersistence()->quote($default);
 		}
-		
+
+        // TODO: move sql query to implementation.
         $query =  'SELECT object, l_language
         			FROM statements 
 		    		WHERE subject = ? 
@@ -137,14 +159,11 @@ public function getPropertyValues( core_kernel_classes_Resource $resource,  core
         
     	
 		if ($one) {
-            // Select first
-			$query .= ' ORDER BY id DESC';
+            // Select first only
+			$query .= ' ORDER BY ' . $this->getModelFactory()->getPropertySortingField() . ' DESC';
 			$query = $platform->limitStatement($query, 1, 0);
-			$result = $this->getPersistence()->query($query,array($resource->getUri(), $property->getUri(), $lang));
-		} else {
-            // Select All
-			$result = $this->getPersistence()->query($query,array($resource->getUri(), $property->getUri(), $lang));
 		}
+        $result = $this->getPersistence()->query($query,array($resource->getUri(), $property->getUri(), $lang));
         
 		// Treat the query result
         if ($result == true) {
@@ -167,8 +186,8 @@ public function getPropertyValues( core_kernel_classes_Resource $resource,  core
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
-     * @param  Property property
+     * @param  core_kernel_classes_Resource resource
+     * @param  core_kernel_classes_Property property
      * @param  string lg
      * @return core_kernel_classes_ContainerCollection
      */
@@ -197,8 +216,8 @@ public function getPropertyValuesByLg( core_kernel_classes_Resource $resource,
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
-     * @param  Property property
+     * @param  core_kernel_classes_Resource resource
+     * @param  core_kernel_classes_Property property
      * @param  string object
      * @param  string lg
      * @return boolean
@@ -207,9 +226,9 @@ public function setPropertyValue( core_kernel_classes_Resource $resource,  core_
     {
         $userId = $this->getServiceLocator()->get(SessionService::SERVICE_ID)->getCurrentUser()->getIdentifier();
         $object  = $object instanceof core_kernel_classes_Resource ? $object->getUri() : (string) $object;
-    	$platform = $this->getPersistence()->getPlatForm();
-        $lang = "";
+
         // Define language if required
+        $lang = '';
         if ($property->isLgDependent()){
         	if ($lg!=null){
         		$lang = $lg;
@@ -217,23 +236,15 @@ public function setPropertyValue( core_kernel_classes_Resource $resource,  core_
                 $lang = $this->getServiceLocator()->get(SessionService::SERVICE_ID)->getCurrentSession()->getDataLanguage();
         	}
         }
-        
-        $query = 'INSERT INTO statements (modelid, subject, predicate, object, l_language, author,epoch)
-        			VALUES  (?, ?, ?, ?, ?, ? , ?)';
-
-        $returnValue = $this->getPersistence()->exec($query, array(
-       		$this->getNewTripleModelId(),
-       		$resource->getUri(),
-       		$property->getUri(),
-       		$object,
-       		$lang,
-            $userId,
-            $platform->getNowExpression()
-        ));
-        
-        
 
-        return (bool) $returnValue;
+        return $this->getModelFactory()->addStatement(
+            $this->getNewTripleModelId(),
+            $resource->getUri(),
+            $property->getUri(),
+            $object,
+            $lang,
+            $userId
+        );
     }
 
     /**
@@ -241,20 +252,21 @@ public function setPropertyValue( core_kernel_classes_Resource $resource,  core_
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
+     * @param  core_kernel_classes_Resource resource
      * @param  array properties
      * @return boolean
      */
     public function setPropertiesValues( core_kernel_classes_Resource $resource, $properties)
     {
-        $returnValue = (bool) false;
+        $returnValue = false;
 
     	if (is_array($properties) && count($properties) > 0) {
         		
             $session = $this->getServiceLocator()->get(SessionService::SERVICE_ID)->getCurrentSession();
-            $platform = $this->getPersistence()->getPlatForm();
 
-            $valuesToInsert = [];
+            $modelId = $this->getNewTripleModelId();
+            $subject = $resource->getUri();
+            $author = $session->getUser()->getIdentifier();
 
             foreach ($properties as $propertyUri => $value) {
                 
@@ -263,6 +275,7 @@ public function setPropertiesValues( core_kernel_classes_Resource $resource, $pr
                 $lang = ($property->isLgDependent() ? $session->getDataLanguage() : '');
                 $formatedValues = [];
                 
+                // @TODO: refactor this
                 if ($value instanceof core_kernel_classes_Resource) {
                     $formatedValues[] = $value->getUri();
                     
@@ -275,22 +288,12 @@ public function setPropertiesValues( core_kernel_classes_Resource $resource, $pr
                 }
                 
                 foreach ($formatedValues as $object) {
-                    $valuesToInsert[] = [
-                        'modelid' => $this->getNewTripleModelId(),
-                        'subject' => $resource->getUri(),
-                        'predicate' => $property->getUri(),
-                        'object' => $object,
-                        'l_language' => $lang,
-                        'author' => $session->getUser()->getIdentifier(),
-                        'epoch' => $platform->getNowExpression()
-                    ];
+                    $returnValue |= $this->getModelFactory()->addStatement($modelId, $subject, $property->getUri(), $object, $lang, $author);
                 }
             }
-
-            $returnValue = $this->getPersistence()->insertMultiple('statements', $valuesToInsert);
         }
-        
-        return (bool) $returnValue;
+
+        return $returnValue;
     }
 
     /**
@@ -298,37 +301,24 @@ public function setPropertiesValues( core_kernel_classes_Resource $resource, $pr
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
-     * @param  Property property
+     * @param  core_kernel_classes_Resource resource
+     * @param  core_kernel_classes_Property property
      * @param  string value
      * @param  string lg
      * @return boolean
      */
     public function setPropertyValueByLg( core_kernel_classes_Resource $resource,  core_kernel_classes_Property $property, $value, $lg)
     {
-        $returnValue = (bool) false;
-
-        
-
-		$platform = $this->getPersistence()->getPlatForm();
 		$userId = $this->getServiceLocator()->get(SessionService::SERVICE_ID)->getCurrentUser()->getIdentifier();
-        
-        $query = 'INSERT INTO statements (modelid,subject,predicate,object,l_language,author,epoch)
-        			VALUES  (?, ?, ?, ?, ?, ?, ?)';
-
-        $returnValue = $this->getPersistence()->exec($query, array(
-       		$this->getNewTripleModelId(),
-       		$resource->getUri(),
-       		$property->getUri(),
-       		$value,
-       		($property->isLgDependent() ? $lg : ''),
-       		$userId,
-            $platform->getNowExpression()
-        ));
-		
-        
 
-        return (bool) $returnValue;
+        return $this->getModelFactory()->addStatement(
+            $this->getNewTripleModelId(),
+            $resource->getUri(),
+            $property->getUri(),
+            $value,
+            ($property->isLgDependent() ? $lg : ''),
+            $userId
+        );
     }
 
     /**
@@ -336,8 +326,8 @@ public function setPropertyValueByLg( core_kernel_classes_Resource $resource,  c
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
-     * @param  Property property
+     * @param  core_kernel_classes_Resource resource
+     * @param  core_kernel_classes_Property property
      * @param  array options
      * @return boolean
      */
@@ -348,7 +338,8 @@ public function removePropertyValues( core_kernel_classes_Resource $resource,  c
 		// Optional params
         $pattern = isset($options['pattern']) && !is_null($options['pattern']) ? $options['pattern'] : null;
         $like = isset($options['like']) && $options['like'] == true ? true : false;
-		
+
+        // TODO: move sql query to implementation.
 		//build query:
 		$query =  'DELETE FROM statements WHERE subject = ? AND predicate = ?';
 		$objectType = $this->getPersistence()->getPlatForm()->getObjectTypeCondition();
@@ -407,33 +398,24 @@ public function removePropertyValues( core_kernel_classes_Resource $resource,  c
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
-     * @param  Property property
+     * @param  core_kernel_classes_Resource resource
+     * @param  core_kernel_classes_Property property
      * @param  string lg
      * @param  array options
      * @return boolean
      */
     public function removePropertyValueByLg( core_kernel_classes_Resource $resource,  core_kernel_classes_Property $property, $lg, $options = array())
     {
-        $returnValue = (bool) false;
-
+        // TODO: move sql query to implementation.
         $sqlQuery = 'DELETE FROM statements WHERE subject = ? and predicate = ? and l_language = ?';
         //be sure the property we try to remove is included in an updatable model
 		$sqlQuery .= ' AND '.$this->getModelWriteSqlCondition();
         
-        $returnValue = $this->getPersistence()->exec($sqlQuery, array (
+        return (bool) $this->getPersistence()->exec($sqlQuery, array (
         	$resource->getUri(),
         	$property->getUri(),
             ($property->isLgDependent() ? $lg : '')
         ));
-        
-    	if (!$returnValue){
-        	$returnValue = false;
-        }
-        
-        
-
-        return (bool) $returnValue;
     }
 
     /**
@@ -447,7 +429,8 @@ public function removePropertyValueByLg( core_kernel_classes_Resource $resource,
     public function getRdfTriples( core_kernel_classes_Resource $resource)
     {
         $returnValue = null;
-        
+
+        // TODO: move sql query to implementation.
         $query = 'SELECT * FROM statements WHERE subject = ? AND '.$this->getModelReadSqlCondition().' ORDER BY predicate';
         $result = $this->getPersistence()->query($query, array($resource->getUri()));
         
@@ -473,16 +456,15 @@ public function getRdfTriples( core_kernel_classes_Resource $resource)
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
-     * @param  Property property
+     * @param  core_kernel_classes_Resource resource
+     * @param  core_kernel_classes_Property property
      * @return array
      */
     public function getUsedLanguages( core_kernel_classes_Resource $resource,  core_kernel_classes_Property $property)
     {
         $returnValue = array();
 
-        
-        
+        // TODO: move sql query to implementation.
     	$sqlQuery = 'SELECT l_language FROM statements WHERE subject = ? AND predicate = ? ';
         $sqlResult = $this->getPersistence()->query($sqlQuery, array (
         	$resource->getUri(),
@@ -504,42 +486,41 @@ public function getUsedLanguages( core_kernel_classes_Resource $resource,  core_
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
+     * @param  core_kernel_classes_Resource resource
      * @param  array excludedProperties
-     * @return core_kernel_classes_Resource
+     * @return core_kernel_classes_Resource|null
+     * @throws common_exception_Error
      */
     public function duplicate( core_kernel_classes_Resource $resource, $excludedProperties = array())
     {
-        $returnValue = null;
         $newUri = $this->getServiceLocator()->get(UriProvider::SERVICE_ID)->provide();
     	$collection = $this->getRdfTriples($resource);
-        
-    	if ($collection->count() > 0) {
-    		
-    		$platform = $this->getPersistence()->getPlatForm();
+
+        if ($collection->count() === 0) {
+            return null;
+        }
+
             $user = $this->getServiceLocator()->get(SessionService::SERVICE_ID)->getCurrentUser()->getIdentifier();
-            $valuesToInsert = [];
-    		
+        $modelId = $this->getNewTripleModelId();
+        $addedRows = false;
+
     		foreach ($collection->getIterator() as $triple) {
     			if (!in_array($triple->predicate, $excludedProperties)) {
-                    $valuesToInsert[] = [
-                        'modelid' => $this->getNewTripleModelId(),
-                        'subject' => $newUri,
-                        'predicate'=> $triple->predicate,
-                        'object' => ($triple->object == null) ? '' : $triple->object,
-                        'l_language' => ($triple->lg == null) ? '' : $triple->lg,
-                        'author' => $user,
-                        'epoch' => $platform->getNowExpression()
-                    ];
+                $addedRows |= $this->getModelFactory()->addStatement(
+                    $modelId,
+                    $newUri,
+                    $triple->predicate,
+                    $triple->object ?? '',
+                    $triple->lg ?? '',
+                    $user
+                );
     			}
 	    	}
-	    	
-        	if ($this->getPersistence()->insertMultiple('statements', $valuesToInsert)) {
-                $returnValue = $this->getModel()->getResource($newUri);
-        	}
-    	}
-        
-        return $returnValue;
+       	if ($addedRows) {
+           	return $this->getModel()->getResource($newUri);
+       	}
+
+        return null;
     }
 
     /**
@@ -547,14 +528,13 @@ public function duplicate( core_kernel_classes_Resource $resource, $excludedProp
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
+     * @param  core_kernel_classes_Resource resource
      * @param  boolean deleteReference
      * @return boolean
      */
     public function delete( core_kernel_classes_Resource $resource, $deleteReference = false)
     {
-        $returnValue = (bool) false;
-
+        // TODO: move sql query to implementation.
 		$query = 'DELETE FROM statements WHERE subject = ? AND '.$this->getModelWriteSqlCondition();
         $returnValue = $this->getPersistence()->exec($query, array($resource->getUri()));
 
@@ -563,6 +543,7 @@ public function delete( core_kernel_classes_Resource $resource, $deleteReference
         	$returnValue = false;
         } 
         else if($deleteReference){
+            // TODO: move sql query to implementation.
         	$sqlQuery = 'DELETE FROM statements WHERE ' . $this->getPersistence()->getPlatForm()->getObjectTypeCondition() . ' = ? AND '.$this->getModelWriteSqlCondition();
         	$return = $this->getPersistence()->exec($sqlQuery, array ($resource->getUri()));
         	
@@ -580,9 +561,10 @@ public function delete( core_kernel_classes_Resource $resource, $deleteReference
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
+     * @param  core_kernel_classes_Resource resource
      * @param  array properties
      * @return array
+     * @throws common_exception_Error
      */
     public function getPropertiesValues( core_kernel_classes_Resource $resource, $properties)
     {
@@ -611,6 +593,8 @@ public function getPropertiesValues( core_kernel_classes_Resource $resource, $pr
         $platform = $this->getPersistence()->getPlatForm();
         $lang = $this->getServiceLocator()->get(SessionService::SERVICE_ID)->getCurrentSession()->getDataLanguage();
         $default = $this->getServiceLocator()->get(UserLanguageServiceInterface::SERVICE_ID)->getDefaultLanguage();
+
+        // TODO: move sql query to implementation.
         //the unique sql query
         $query =  'SELECT predicate, object, l_language 
             FROM statements 
@@ -641,8 +625,8 @@ public function getPropertiesValues( core_kernel_classes_Resource $resource, $pr
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
-     * @param  Class class
+     * @param  core_kernel_classes_Resource resource
+     * @param  core_kernel_classes_Class class
      * @return boolean
      */
     public function setType( core_kernel_classes_Resource $resource,  core_kernel_classes_Class $class)
@@ -656,16 +640,13 @@ public function setType( core_kernel_classes_Resource $resource,  core_kernel_cl
      *
      * @access public
      * @author Joel Bout, <joel.bout@tudor.lu>
-     * @param  Resource resource
-     * @param  Class class
+     * @param  core_kernel_classes_Resource resource
+     * @param  core_kernel_classes_Class class
      * @return boolean
      */
     public function removeType( core_kernel_classes_Resource $resource,  core_kernel_classes_Class $class)
     {
-        $returnValue = (bool) false;
-
-        
-        
+        // TODO: move sql query to implementation.
         $query =  'DELETE FROM statements 
 		    		WHERE subject = ? AND predicate = ? AND '. $this->getPersistence()->getPlatForm()->getObjectTypeCondition() .' = ?';
         
diff --git a/core/kernel/persistence/smoothsql/class.SmoothIterator.php b/core/kernel/persistence/smoothsql/class.SmoothIterator.php
index 872e44146..15e182c0a 100644
--- a/core/kernel/persistence/smoothsql/class.SmoothIterator.php
+++ b/core/kernel/persistence/smoothsql/class.SmoothIterator.php
@@ -18,6 +18,9 @@
  *
  */
 
+use core_kernel_api_ModelFactory as ModelFactory;
+use oat\oatbox\service\ServiceManager;
+
 /**
  * Iterator over all triples
  * 
@@ -33,10 +36,11 @@ class core_kernel_persistence_smoothsql_SmoothIterator
      * @param array $modelIds
      */
     public function __construct(common_persistence_SqlPersistence $persistence, $modelIds = null) {
-        $query = 'SELECT * FROM statements '
-            .(is_null($modelIds) ? '' : 'WHERE modelid IN ('.implode(',', $modelIds).') ')
-            .'ORDER BY id';
-        parent::__construct($persistence, $query);
+
+        $serviceManager = ServiceManager::getServiceManager();
+        /** @var ModelFactory $modelFactory */
+        $modelFactory = $serviceManager->get(ModelFactory::SERVICE_ID);
+        parent::__construct($persistence, $modelFactory->getIteratorQuery($modelIds));
     }
     
     /**
@@ -46,7 +50,8 @@ public function __construct(common_persistence_SqlPersistence $persistence, $mod
      */
     function current() {
         $statement = parent::current();
-        
+
+        // TODO: create a constructor
         $triple = new core_kernel_classes_Triple();
         $triple->modelid = $statement["modelid"];
         $triple->subject = $statement["subject"];
@@ -57,4 +62,4 @@ function current() {
         $triple->author = $statement["author"];
         return $triple;
     }
-}
\ No newline at end of file
+}
diff --git a/core/kernel/persistence/smoothsql/class.SmoothRdf.php b/core/kernel/persistence/smoothsql/class.SmoothRdf.php
index 8baa34e07..445a543e5 100644
--- a/core/kernel/persistence/smoothsql/class.SmoothRdf.php
+++ b/core/kernel/persistence/smoothsql/class.SmoothRdf.php
@@ -18,6 +18,7 @@
  *
  */
 
+use core_kernel_api_ModelFactory as ModelFactory;
 use oat\generis\model\data\RdfInterface;
 use oat\generis\model\OntologyRdf;
 use oat\generis\model\OntologyRdfs;
@@ -27,7 +28,7 @@
 
 /**
  * Implementation of the RDF interface for the smooth sql driver
- * 
+ *
  * @author joel bout <joel@taotesting.com>
  * @package generis
  */
@@ -38,15 +39,15 @@ class core_kernel_persistence_smoothsql_SmoothRdf
      * @var core_kernel_persistence_smoothsql_SmoothModel
      */
     private $model;
-    
+
     public function __construct(core_kernel_persistence_smoothsql_SmoothModel $model) {
         $this->model = $model;
     }
-    
+
     protected function getPersistence() {
         return $this->model->getPersistence();
     }
-    
+
     /**
      * (non-PHPdoc)
      * @see \oat\generis\model\data\RdfInterface::get()
@@ -54,7 +55,7 @@ protected function getPersistence() {
     public function get($subject, $predicate) {
         throw new \common_Exception('Not implemented');
     }
-    
+
     /**
      * (non-PHPdoc)
      * @see \oat\generis\model\data\RdfInterface::add()
@@ -63,15 +64,26 @@ public function add(\core_kernel_classes_Triple $triple) {
         if (!in_array($triple->modelid, $this->model->getReadableModels())) {
             $this->model->addReadableModel($triple->modelid);
         }
-        $query = "INSERT INTO statements ( modelId, subject, predicate, object, l_language, epoch, author) VALUES ( ? , ? , ? , ? , ? , ?, ?);";
-        $success = $this->getPersistence()->exec($query, array($triple->modelid, $triple->subject, $triple->predicate, $triple->object, is_null($triple->lg) ? '' : $triple->lg, $this->getPersistence()->getPlatForm()->getNowExpression(), is_null($triple->author) ? '' : $triple->author));
+
+        /** @var ModelFactory $modelFactory */
+        $modelFactory = $this->getServiceManager()->get(ModelFactory::SERVICE_ID);
+        $returnValue = $modelFactory->addStatement(
+            $triple->modelid,
+            $triple->subject,
+            $triple->predicate,
+            $triple->object,
+            is_null($triple->lg) ? '' : $triple->lg,
+            is_null($triple->author) ? '' : $triple->author
+        );
+
         if ($triple->predicate == OntologyRdfs::RDFS_SUBCLASSOF || $triple->predicate == OntologyRdf::RDF_TYPE) {
             $eventManager = $this->getServiceManager()->get(EventManager::CONFIG_ID);
             $eventManager->trigger(new ResourceCreated(new core_kernel_classes_Resource($triple->subject)));
         }
-        return $success;
+
+        return $returnValue;
     }
-    
+
     /**
      * (non-PHPdoc)
      * @see \oat\generis\model\data\RdfInterface::remove()
@@ -80,7 +92,7 @@ public function remove(\core_kernel_classes_Triple $triple) {
         $query = "DELETE FROM statements WHERE subject = ? AND predicate = ? AND object = ? AND l_language = ?;";
         return $this->getPersistence()->exec($query, array($triple->subject, $triple->predicate, $triple->object, is_null($triple->lg) ? '' : $triple->lg));
     }
-    
+
     /**
      * (non-PHPdoc)
      * @see \oat\generis\model\data\RdfInterface::search()
@@ -88,13 +100,13 @@ public function remove(\core_kernel_classes_Triple $triple) {
     public function search($predicate, $object) {
         throw new \common_Exception('Not implemented');
     }
-    
+
     public function getIterator() {
         return new core_kernel_persistence_smoothsql_SmoothIterator($this->getPersistence());
     }
-    
+
     public function getServiceManager()
     {
         return ServiceManager::getServiceManager();
     }
-}
\ No newline at end of file
+}
diff --git a/core/kernel/persistence/smoothsql/install/SmoothRdsModel.php b/core/kernel/persistence/smoothsql/install/SmoothRdsModel.php
index ba3951414..21b58cd2f 100644
--- a/core/kernel/persistence/smoothsql/install/SmoothRdsModel.php
+++ b/core/kernel/persistence/smoothsql/install/SmoothRdsModel.php
@@ -17,42 +17,32 @@
  * Copyright (c) 2018 (original work) Open Assessment Technologies SA (under the project TAO-PRODUCT);
  *
  */
-namespace   oat\generis\model\kernel\persistence\smoothsql\install;
+
+namespace oat\generis\model\kernel\persistence\smoothsql\install;
 
 use Doctrine\DBAL\Schema\Schema;
+use core_kernel_api_ModelFactory as ModelFactory;
+use oat\oatbox\service\ConfigurableService;
+
 /**
  * Helper to setup the required tables for generis smoothsql
  */
-class SmoothRdsModel {
-
+class SmoothRdsModel extends ConfigurableService
+{
     /**
-     * 
+     *
      * @param Schema $schema
+     *
      * @return \Doctrine\DBAL\Schema\Schema
      */
-    public static function addSmoothTables(Schema $schema)
+    public function addSmoothTables(Schema $schema)
     {
-        $table = $schema->createTable("models");
-        $table->addColumn('modelid', "integer",["notnull" => true,"autoincrement" => true]);
-        $table->addColumn('modeluri', "string", ["length" => 255,"default" => null]);
-        $table->addOption('engine' , 'MyISAM');
-        $table->setPrimaryKey(['modelid']);
+        /** @var ModelFactory $modelFactory */
+        $modelFactory = $this->getServiceLocator()->get(ModelFactory::SERVICE_ID);
 
-        $table = $schema->createTable("statements");
-        $table->addColumn("modelid", "integer",["notnull" => true,"default" => 0]);
-        $table->addColumn("subject", "string",["length" => 255,"default" => null]);
-        $table->addColumn("predicate", "string",["length" => 255,"default" => null]);
-        $table->addColumn("object", "text", ["default" => null,"notnull" => false]);
-            
-        $table->addColumn("l_language", "string",["length" => 255,"default" => null,"notnull" => false]);
-        $table->addColumn("id", "integer",["notnull" => true,"autoincrement" => true]);
-        $table->addColumn("author", "string",["length" => 255,"default" => null,"notnull" => false]);
-        $table->setPrimaryKey(["id"]);
-        $table->addOption('engine' , 'MyISAM');
-        $table->addColumn("epoch", "string" , ["notnull" => null]);
+        $modelFactory->createModelsTable($schema);
+        $modelFactory->createStatementsTable($schema);
 
-        $table->addIndex(["subject","predicate"],"k_sp", [], ['lengths' => [164,164]]);
-        $table->addIndex(["predicate","object"],"k_po", [], ['lengths' => [164,164]]);
         return $schema;
     }
 }
diff --git a/helpers/UuidPrimaryKeyTrait.php b/helpers/UuidPrimaryKeyTrait.php
new file mode 100644
index 000000000..dbb9f69f5
--- /dev/null
+++ b/helpers/UuidPrimaryKeyTrait.php
@@ -0,0 +1,39 @@
+<?php
+/**
+ * This program 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; under version 2
+ * of the License (non-upgradable).
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ * Copyright (c) 2019 (original work) Open Assessment Technologies SA (under the project TAO-PRODUCT);
+ *
+ * @author "Julien Sébire, <julien@taotesting.com>"
+ * @license GPLv2
+ * @package generis
+ *
+ */
+namespace oat\generis\Helper;
+
+use Ramsey\Uuid\Uuid;
+
+trait UuidPrimaryKeyTrait
+{
+    /**
+     * Generates a unique, not auto-increment based, primary key.
+     * @return string
+     * @throws \Exception
+     */
+    public function getUniquePrimaryKey()
+    {
+        return Uuid::uuid4();
+    }
+}
diff --git a/test/GenerisTestCase.php b/test/GenerisTestCase.php
index a8d2353ce..184a684e4 100755
--- a/test/GenerisTestCase.php
+++ b/test/GenerisTestCase.php
@@ -19,6 +19,8 @@
  */
 namespace oat\generis\test;
 
+use core_kernel_api_ModelFactory as ModelFactory;
+use oat\generis\model\kernel\api\RdsModelFactory;
 use oat\generis\model\kernel\persistence\smoothsql\install\SmoothRdsModel;
 use oat\oatbox\user\UserLanguageServiceInterface;
 use oat\oatbox\session\SessionService;
@@ -42,11 +44,7 @@ protected function getOntologyMock()
         $pm = $this->getSqlMock('mockSql');
         $rds = $pm->getPersistenceById('mockSql');
         $schema = $rds->getSchemaManager()->createSchema();
-        $schema = SmoothRdsModel::addSmoothTables($schema);
-        $queries = $rds->getPlatform()->schemaToSql($schema);
-        foreach ($queries as $query){
-            $rds->query($query);
-        }
+        $smoothRdsModel = new SmoothRdsModel();
         
         $session = new \common_session_AnonymousSession();
         $sl = $this->getServiceLocatorMock([
@@ -56,6 +54,7 @@ protected function getOntologyMock()
             EventManager::SERVICE_ID => new EventManager(),
             LoggerService::SERVICE_ID => $this->prophesize(LoggerInterface::class)->reveal(),
             UriProvider::SERVICE_ID => new Bin2HexUriProvider([Bin2HexUriProvider::OPTION_NAMESPACE => 'http://ontology.mock/bin2hex#']),
+            ModelFactory::SERVICE_ID => new RdsModelFactory(),
             'smoothcache' => new \common_cache_NoCache()
         ]);
         $session->setServiceLocator($sl);
@@ -67,6 +66,13 @@ protected function getOntologyMock()
             'cache' => 'smoothcache'
         ]);
         $model->setServiceLocator($sl);
+        $smoothRdsModel->setServiceLocator($sl);
+
+        $schema = $smoothRdsModel->addSmoothTables($schema);
+        $queries = $rds->getPlatform()->schemaToSql($schema);
+        foreach ($queries as $query){
+            $rds->query($query);
+        }
 
         return $model;
     }
diff --git a/test/unit/model/persistence/smoothsql/SmoothModelIteratorTest.php b/test/integration/model/persistence/smoothsql/SmoothModelIteratorTest.php
similarity index 98%
rename from test/unit/model/persistence/smoothsql/SmoothModelIteratorTest.php
rename to test/integration/model/persistence/smoothsql/SmoothModelIteratorTest.php
index ae50e901b..df96ac66d 100644
--- a/test/unit/model/persistence/smoothsql/SmoothModelIteratorTest.php
+++ b/test/integration/model/persistence/smoothsql/SmoothModelIteratorTest.php
@@ -17,7 +17,7 @@
  * Copyright (c) (original work) 2015 Open Assessment Technologies SA
  * 
  */
-namespace oat\generis\test\unit\model\persistence\smoothsql;
+namespace oat\generis\test\integration\model\persistence\smoothsql;
 
 use Prophecy\Promise\ReturnPromise;
 use Prophecy\Argument;
diff --git a/test/unit/model/persistence/smoothsql/SmoothRdfTest.php b/test/integration/model/persistence/smoothsql/SmoothRdfTest.php
similarity index 98%
rename from test/unit/model/persistence/smoothsql/SmoothRdfTest.php
rename to test/integration/model/persistence/smoothsql/SmoothRdfTest.php
index b2b5128bf..1d8cdda1e 100644
--- a/test/unit/model/persistence/smoothsql/SmoothRdfTest.php
+++ b/test/integration/model/persistence/smoothsql/SmoothRdfTest.php
@@ -17,7 +17,7 @@
  * Copyright (c) (original work) 2015 Open Assessment Technologies SA
  * 
  */
-namespace oat\generis\test\unit\model\persistence\smoothsql;
+namespace oat\generis\test\integration\model\persistence\smoothsql;
 
 use \core_kernel_persistence_smoothsql_SmoothRdf;
 use Prophecy\Prophet;
@@ -171,4 +171,4 @@ public function testRemove()
     }
 }
 
-?>
\ No newline at end of file
+?>
diff --git a/test/unit/OntologyMockTest.php b/test/unit/OntologyMockTest.php
index f9b023b7e..4b1dbefee 100755
--- a/test/unit/OntologyMockTest.php
+++ b/test/unit/OntologyMockTest.php
@@ -22,24 +22,28 @@
 use oat\generis\model\data\Model;
 use oat\generis\test\GenerisTestCase;
 use oat\generis\model\data\Ontology;
+use core_kernel_persistence_smoothsql_SmoothModel as SmoothModel;
 /**
  * 
  */
 class OntologyMockTest extends GenerisTestCase
 {
-    public function testModel()
+    /** @var SmoothModel */
+    private $subject;
+    
+    public function setUp()
     {
-        $model = $this->getOntologyMock();
-        $this->assertInstanceOf(Model::class, $model);
-        return $model;
+        $this->subject = $this->getOntologyMock();
     }
 
-    /**
-     * @depends testModel
-     */
-    public function testSetLabel($model)
+    public function testOntologyMockClass()
     {
-        $resource = $model->getResource('http://testing');
+        $this->assertInstanceOf(Model::class, $this->subject);
+    }
+
+    public function testSetLabel()
+    {
+        $resource = $this->subject->getResource('http://testing');
         $this->assertInstanceOf(\core_kernel_classes_Resource::class, $resource);
         $label = $resource->getLabel();
         $this->assertEquals('', $label);
@@ -48,12 +52,9 @@ public function testSetLabel($model)
         $this->assertEquals('magic', $label);
     }
 
-    /**
-     * @depends testModel
-     */
-    public function testCreateInstance($model)
+    public function testCreateInstance()
     {
-        $class = $model->getClass('http://testing#class');
+        $class = $this->subject->getClass('http://testing#class');
         $this->assertInstanceOf(\core_kernel_classes_Class::class, $class);
         // with URI
         $resource = $class->createInstance('sample', 'comment', 'http://testing#resource');
@@ -61,15 +62,11 @@ public function testCreateInstance($model)
         // without URI
         $resource = $class->createInstance('sample');
         $this->assertInstanceOf(\core_kernel_classes_Resource::class, $resource);
-        return $resource;
     }
 
-    /**
-     * @depends testModel
-     */
-    public function testDuplicateInstance(Ontology $model)
+    public function testDuplicateInstance()
     {
-        $class = $model->getClass('http://testing#class');
+        $class = $this->subject->getClass('http://testing#class');
         $this->assertInstanceOf(\core_kernel_classes_Class::class, $class);
         $resource = $class->createInstance('original');
         $this->assertInstanceOf(\core_kernel_classes_Resource::class, $resource);
@@ -79,11 +76,11 @@ public function testDuplicateInstance(Ontology $model)
         $this->assertNotEquals($resource, $resourceClone);
     }
 
-    /**
-     * @depends testCreateInstance
-     */
-    public function testDeleteInstance(\core_kernel_classes_Resource $resource)
+    public function testDeleteInstance()
     {
+        $class = $this->subject->getClass('http://testing#class');
+        $resource = $class->createInstance('sample');
+
         $this->assertTrue($resource->exists());
         $resource->delete();
         $this->assertFalse($resource->exists());