diff --git a/composer.json b/composer.json
index a03178c8..299804c3 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,6 @@
     },
     "require-dev": {
         "phpspec/phpspec": "~2.1@dev",
-        "henrikbjorn/phpspec-code-coverage": "0.2.*",
         "satooshi/php-coveralls": "0.6.*"
     },
     "autoload": {
diff --git a/spec/Happyr/DoctrineSpecification/DoctrineTransformerSpec.php b/spec/Happyr/DoctrineSpecification/DoctrineTransformerSpec.php
new file mode 100644
index 00000000..cb967acf
--- /dev/null
+++ b/spec/Happyr/DoctrineSpecification/DoctrineTransformerSpec.php
@@ -0,0 +1,179 @@
+<?php
+
+namespace spec\Happyr\DoctrineSpecification;
+
+use Doctrine\ORM\Query;
+use Doctrine\ORM\Query\Expr;
+use Doctrine\ORM\QueryBuilder;
+use Happyr\DoctrineSpecification\Filter\Equals;
+use Happyr\DoctrineSpecification\Filter\GreaterOrEqualThan;
+use Happyr\DoctrineSpecification\Filter\GreaterThan;
+use Happyr\DoctrineSpecification\Filter\In;
+use Happyr\DoctrineSpecification\Filter\IsNotNull;
+use Happyr\DoctrineSpecification\Filter\IsNull;
+use Happyr\DoctrineSpecification\Filter\LessOrEqualThan;
+use Happyr\DoctrineSpecification\Filter\LessThan;
+use Happyr\DoctrineSpecification\Filter\Like;
+use Happyr\DoctrineSpecification\Filter\NotEquals;
+use Happyr\DoctrineSpecification\Logic\AndX;
+use Happyr\DoctrineSpecification\Logic\Not;
+use Happyr\DoctrineSpecification\Logic\OrX;
+use Happyr\DoctrineSpecification\ParametersBag;
+use Happyr\DoctrineSpecification\Specification;
+use Happyr\DoctrineSpecification\Transformer\DoctrineTransformer;
+use PhpSpec\ObjectBehavior;
+use Prophecy\Argument;
+
+/**
+ * @mixin DoctrineTransformer
+ */
+class DoctrineTransformerSpec extends ObjectBehavior
+{
+    function let(QueryBuilder $queryBuilder, Expr $expr)
+    {
+        $queryBuilder->expr()->willReturn($expr);
+        $this->beConstructedWith($queryBuilder);
+    }
+
+    function it_is_initializable()
+    {
+        $this->shouldHaveType('Happyr\DoctrineSpecification\DoctrineTransformer');
+    }
+
+    function it_should_transform_is_not_null(Expr $expr, ParametersBag $parameters)
+    {
+        $expr->isNotNull('field')->willReturn('field IS NOT NULL');
+        $this->getDqlPart(new IsNotNull('field'), $parameters)->shouldReturn('field IS NOT NULL');
+    }
+
+    function it_should_transform_is_null(Expr $expr, ParametersBag $parameters)
+    {
+        $expr->isNull('field')->willReturn('field IS NULL');
+
+        $this->getDqlPart(new IsNull('field'), $parameters)->shouldReturn('field IS NULL');
+    }
+
+    function it_should_transform_equals(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->getLastName()->willReturn('?1');
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $expr->eq('field', '?1')->willReturn('field = ?1');
+
+        $this->getDqlPart(new Equals('field', 'value'), $parameters)->shouldReturn('field = ?1');
+    }
+
+    function it_should_transform_greater_than_or_equals(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $parameters->getLastName()->willReturn('?1');
+        $expr->gte('field', '?1')->willReturn('field >= ?1');
+
+        $this->getDqlPart(new GreaterOrEqualThan('field', 'value'), $parameters)->shouldReturn('field >= ?1');
+    }
+
+    function it_should_transform_greater_than(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $parameters->getLastName()->willReturn('?1');
+        $expr->gt('field', '?1')->willReturn('field > ?1');
+
+        $this->getDqlPart(new GreaterThan('field', 'value'), $parameters)->shouldReturn('field > ?1');
+    }
+
+    function it_should_transform_in(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $parameters->getLastName()->willReturn('?1');
+        $expr->in('field', '?1')->willReturn('field IN (\'?1\')');
+
+        $this->getDqlPart(new In('field', [1,2,3]), $parameters)->shouldReturn('field IN (\'?1\')');
+    }
+
+    function it_should_transform_less_or_equals(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $parameters->getLastName()->willReturn('?1');
+        $expr->lte('field', '?1')->willReturn('field <= ?1');
+
+        $this->getDqlPart(new LessOrEqualThan('field', 'value'), $parameters)->shouldReturn('field <= ?1');
+    }
+
+    function it_should_transform_less_than_or_equals(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $parameters->getLastName()->willReturn('?1');
+        $expr->lt('field', '?1')->willReturn('field < ?1');
+
+        $this->getDqlPart(new LessThan('field', 'value'), $parameters)->shouldReturn('field < ?1');
+    }
+
+    function it_should_transform_like_contains(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $parameters->getLastName()->willReturn('?1');
+        $expr->like('field', '?1')->willReturn('field like ?1');
+
+        $this->getDqlPart(new Like('field', 'value', Like::CONTAINS), $parameters)->shouldReturn('field like ?1');
+    }
+
+    function it_should_transform_like_starts_with(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $parameters->getLastName()->willReturn('?1');
+        $expr->like('field', '?1')->willReturn('field like ?1');
+
+        $this->getDqlPart(new Like('field', 'value', Like::STARTS_WITH), $parameters)->shouldReturn('field like ?1');
+    }
+
+    function it_should_transform_ends_with(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $parameters->getLastName()->willReturn('?1');
+        $expr->like('field', '?1')->willReturn('field like ?1');
+
+        $this->getDqlPart(new Like('field', 'value', Like::ENDS_WITH), $parameters)->shouldReturn('field like ?1');
+    }
+
+    function it_should_transform_not_equals(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $parameters->getLastName()->willReturn('?1');
+        $expr->neq('field', '?1')->willReturn('field <> ?1');
+
+        $this->getDqlPart(new NotEquals('field', 'value'), $parameters)->shouldReturn('field <> ?1');
+    }
+
+    function it_should_transform_not(Expr $expr, ParametersBag $parameters)
+    {
+        $parameters->getLastName()->willReturn('?1');
+        $parameters->add(Argument::any())->shouldBeCalled();
+        $expr->eq('field', '?1')->willReturn('field = ?1');
+        $expr->not('field = ?1')->willReturn('NOT (field = ?1)');
+
+        $this->getDqlPart(new Not(new Equals('field', 'value')), $parameters)->shouldReturn('NOT (field = ?1)');
+    }
+
+    function it_should_transform_and(Expr $expr)
+    {
+        $parameters = new ParametersBag();
+
+        $expr->eq('field', '?1')->willReturn('field = ?1');
+        $expr->eq('field', '?2')->willReturn('field = ?2');
+        $expr->andX('field = ?1', 'field = ?2')->willReturn('field = ?1 AND field = ?2');
+
+        $this->getDqlPart(new AndX(new Equals('field', 'value1'), new Equals('field', 'value2')), $parameters)->shouldReturn('field = ?1 AND field = ?2');
+    }
+
+    function it_should_transform_or(Expr $expr)
+    {
+        $parameters = new ParametersBag();
+
+        $expr->eq('field', '?1')->willReturn('field = ?1');
+        $expr->eq('field', '?2')->willReturn('field = ?2');
+        $expr->orX('field = ?1', 'field = ?2')->willReturn('field = ?1 OR field = ?2');
+
+        $this->getDqlPart(new OrX(new Equals('field', 'value1'), new Equals('field', 'value2')), $parameters)->shouldReturn('field = ?1 OR field = ?2');
+    }
+
+
+}
diff --git a/spec/Happyr/DoctrineSpecification/EntitySpecificationRepositorySpec.php b/spec/Happyr/DoctrineSpecification/EntitySpecificationRepositorySpec.php
deleted file mode 100644
index 79573fff..00000000
--- a/spec/Happyr/DoctrineSpecification/EntitySpecificationRepositorySpec.php
+++ /dev/null
@@ -1,70 +0,0 @@
-<?php
-
-namespace spec\Happyr\DoctrineSpecification;
-
-use Doctrine\ORM\AbstractQuery;
-use Doctrine\ORM\EntityManager;
-use Doctrine\ORM\Mapping\ClassMetadata;
-use Doctrine\ORM\Query\Expr;
-use Doctrine\ORM\QueryBuilder;
-use Happyr\DoctrineSpecification\EntitySpecificationRepository;
-use Happyr\DoctrineSpecification\Result\ResultModifier;
-use Happyr\DoctrineSpecification\Specification;
-use PhpSpec\ObjectBehavior;
-use Prophecy\Argument;
-
-/**
- * @mixin EntitySpecificationRepository
- */
-class EntitySpecificationRepositorySpec extends ObjectBehavior
-{
-    private $alias = 'e';
-    private $expression = 'expression';
-    private $result = 'result';
-
-    function let(EntityManager $entityManager, ClassMetadata $classMetadata)
-    {
-        $this->beConstructedWith($entityManager, $classMetadata);
-    }
-
-    function it_matches_a_specification_without_result_modifier(
-        Specification $specification,
-        EntityManager $entityManager,
-        QueryBuilder $qb,
-        AbstractQuery $query
-    )
-    {
-        $this->prepareStubs($specification, $entityManager, $qb, $query);
-
-        $specification->modify($qb, $this->alias)->shouldBeCalled();
-
-        $this->match($specification)->shouldReturn($this->result);
-    }
-
-    function it_matches_a_specification_with_result_modifier(
-        Specification $specification,
-        EntityManager $entityManager,
-        QueryBuilder $qb,
-        AbstractQuery $query,
-        ResultModifier $modifier
-    )
-    {
-        $this->prepareStubs($specification, $entityManager, $qb, $query);
-
-        $specification->modify($qb, $this->alias)->shouldBeCalled();
-        $modifier->modify($query)->shouldBeCalled();
-
-        $this->match($specification, $modifier)->shouldReturn($this->result);
-    }
-
-    private function prepareStubs(Specification $specification, EntityManager $entityManager, QueryBuilder $qb, AbstractQuery $query)
-    {
-        $entityManager->createQueryBuilder()->willReturn($qb);
-        $specification->getFilter($qb, $this->alias)->willReturn($this->expression);
-        $qb->from(Argument::any(), $this->alias)->willReturn($qb);
-        $qb->select($this->alias)->willReturn($qb);
-        $qb->where($this->expression)->willReturn($qb);
-        $qb->getQuery()->willReturn($query);
-        $query->execute()->willReturn($this->result);
-    }
-}
diff --git a/spec/Happyr/DoctrineSpecification/Filter/ComparisonSpec.php b/spec/Happyr/DoctrineSpecification/Filter/ComparisonSpec.php
deleted file mode 100644
index fd045293..00000000
--- a/spec/Happyr/DoctrineSpecification/Filter/ComparisonSpec.php
+++ /dev/null
@@ -1,54 +0,0 @@
-<?php
-
-namespace spec\Happyr\DoctrineSpecification\Filter;
-
-use Doctrine\Common\Collections\ArrayCollection;
-use Doctrine\ORM\QueryBuilder;
-use Happyr\DoctrineSpecification\Filter\Comparison;
-use PhpSpec\ObjectBehavior;
-use Prophecy\Argument;
-
-/**
- * @mixin Comparison
- */
-class ComparisonSpec extends ObjectBehavior
-{
-    function let()
-    {
-        $this->beConstructedWith(Comparison::GT, 'age', 18, 'a');
-    }
-
-    function it_is_an_expression()
-    {
-        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Filter');
-    }
-    
-    function it_returns_comparison_object(QueryBuilder $qb, ArrayCollection $parameters)
-    {
-        $qb->getParameters()->willReturn($parameters);
-        $parameters->count()->willReturn(10);
-
-        $qb->setParameter('comparison_10', 18)->shouldBeCalled();
-
-        $comparison = $this->getFilter($qb, null);
-
-        $comparison->shouldReturn('a.age > :comparison_10');
-    }
-
-    function it_uses_comparison_specific_dql_alias_if_passed(QueryBuilder $qb, ArrayCollection $parameters)
-    {
-        $this->beConstructedWith(Comparison::GT, 'age', 18, null);
-
-        $qb->getParameters()->willReturn($parameters);
-        $parameters->count()->willReturn(10);
-
-        $qb->setParameter('comparison_10', 18)->shouldBeCalled();
-
-        $this->getFilter($qb, 'x')->shouldReturn('x.age > :comparison_10');
-    }
-
-    function it_validates_operator()
-    {
-        $this->shouldThrow('Happyr\DoctrineSpecification\Exception\InvalidArgumentException')->during('__construct', array('==', 'age', 18, null));
-    }
-}
diff --git a/spec/Happyr/DoctrineSpecification/Filter/EqualsSpec.php b/spec/Happyr/DoctrineSpecification/Filter/EqualsSpec.php
new file mode 100644
index 00000000..982472ad
--- /dev/null
+++ b/spec/Happyr/DoctrineSpecification/Filter/EqualsSpec.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace spec\Happyr\DoctrineSpecification\Filter;
+
+use Happyr\DoctrineSpecification\Filter\ComparisonInterface;
+use PhpSpec\ObjectBehavior;
+
+/**
+ * @mixin Comparison
+ */
+class EqualsSpec extends ObjectBehavior
+{
+    function let()
+    {
+        $this->beConstructedWith('field', 'value');
+    }
+
+    function it_is_a_filter()
+    {
+        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Base\FilterInterface');
+    }
+
+    function it_has_field_name()
+    {
+        $this->getField()->shouldReturn('field');
+    }
+
+    function it_has_field_value()
+    {
+        $this->getValue()->shouldReturn('value');
+    }
+}
diff --git a/spec/Happyr/DoctrineSpecification/Filter/GreaterOrEqualThanSpec.php b/spec/Happyr/DoctrineSpecification/Filter/GreaterOrEqualThanSpec.php
new file mode 100644
index 00000000..f1603e2f
--- /dev/null
+++ b/spec/Happyr/DoctrineSpecification/Filter/GreaterOrEqualThanSpec.php
@@ -0,0 +1,30 @@
+<?php
+
+
+namespace spec\Happyr\DoctrineSpecification\Filter;
+
+use PhpSpec\ObjectBehavior;
+use Prophecy\Argument;
+
+class GreaterOrEqualThanSpec extends ObjectBehavior
+{
+    function let()
+    {
+        $this->beConstructedWith('field', 'value');
+    }
+
+    function it_is_a_filter()
+    {
+        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Base\FilterInterface');
+    }
+
+    function it_has_field_name()
+    {
+        $this->getField()->shouldReturn('field');
+    }
+
+    function it_has_field_value()
+    {
+        $this->getValue()->shouldReturn('value');
+    }
+}
diff --git a/spec/Happyr/DoctrineSpecification/Filter/GreaterThanSpec.php b/spec/Happyr/DoctrineSpecification/Filter/GreaterThanSpec.php
new file mode 100644
index 00000000..3aab5cf1
--- /dev/null
+++ b/spec/Happyr/DoctrineSpecification/Filter/GreaterThanSpec.php
@@ -0,0 +1,30 @@
+<?php
+
+
+namespace spec\Happyr\DoctrineSpecification\Filter;
+
+use PhpSpec\ObjectBehavior;
+use Prophecy\Argument;
+
+class GreaterThanSpec extends ObjectBehavior
+{
+    function let()
+    {
+        $this->beConstructedWith('field', 'value');
+    }
+
+    function it_is_a_filter()
+    {
+        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Base\FilterInterface');
+    }
+
+    function it_has_field_name()
+    {
+        $this->getField()->shouldReturn('field');
+    }
+
+    function it_has_field_value()
+    {
+        $this->getValue()->shouldReturn('value');
+    }
+}
diff --git a/spec/Happyr/DoctrineSpecification/Filter/InSpec.php b/spec/Happyr/DoctrineSpecification/Filter/InSpec.php
index bf526425..0867af04 100644
--- a/spec/Happyr/DoctrineSpecification/Filter/InSpec.php
+++ b/spec/Happyr/DoctrineSpecification/Filter/InSpec.php
@@ -2,43 +2,31 @@
 
 namespace spec\Happyr\DoctrineSpecification\Filter;
 
-use Doctrine\Common\Collections\ArrayCollection;
-use Doctrine\ORM\Query\Expr;
-use Doctrine\ORM\QueryBuilder;
 use Happyr\DoctrineSpecification\Filter\In;
 use PhpSpec\ObjectBehavior;
-use Prophecy\Argument;
 
 /**
  * @mixin In
  */
 class InSpec extends ObjectBehavior
 {
-    private $field='foobar';
-
-    private $value=array('bar', 'baz');
-
     function let()
     {
-        $this->beConstructedWith($this->field, $this->value, 'a');
+        $this->beConstructedWith('field', 'value');
     }
 
-    function it_is_an_expression()
+    function it_is_a_filter()
     {
-        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Filter');
+        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Base\FilterInterface');
     }
 
-    function it_returns_expression_func_object(QueryBuilder $qb, ArrayCollection $parameters, Expr $expr)
+    function it_has_field_name()
     {
-        $dqlAlias = 'a';
-        $qb->expr()->willReturn($expr);
-        $expr->in(sprintf('%s.%s', $dqlAlias, $this->field), ':in_10')->shouldBeCalled();
-
-        $qb->getParameters()->willReturn($parameters);
-        $parameters->count()->willReturn(10);
-
-        $qb->setParameter('in_10', $this->value)->shouldBeCalled();
+        $this->getField()->shouldReturn('field');
+    }
 
-        $this->getFilter($qb, null);
+    function it_has_field_value()
+    {
+        $this->getValue()->shouldReturn('value');
     }
 }
diff --git a/spec/Happyr/DoctrineSpecification/Filter/IsNotNullSpec.php b/spec/Happyr/DoctrineSpecification/Filter/IsNotNullSpec.php
index ef208622..f667d8c5 100644
--- a/spec/Happyr/DoctrineSpecification/Filter/IsNotNullSpec.php
+++ b/spec/Happyr/DoctrineSpecification/Filter/IsNotNullSpec.php
@@ -2,51 +2,26 @@
 
 namespace spec\Happyr\DoctrineSpecification\Filter;
 
-use Doctrine\ORM\Query\Expr;
-use Doctrine\ORM\QueryBuilder;
 use Happyr\DoctrineSpecification\Filter\IsNotNull;
 use PhpSpec\ObjectBehavior;
-use Prophecy\Argument;
 
 /**
  * @mixin IsNotNull
  */
 class IsNotNullSpec extends ObjectBehavior
 {
-    private $field='foobar';
-
-    private $dqlAlias = 'a';
-
     function let()
     {
-        $this->beConstructedWith($this->field, $this->dqlAlias);
-    }
-
-    function it_is_an_expression()
-    {
-        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Filter');
+        $this->beConstructedWith('field');
     }
 
-    /**
-     * returns expression func object
-     */
-    function it_calls_not_null(QueryBuilder $qb, Expr $expr)
+    function it_is_a_filter()
     {
-        $expression = 'a.foobar is not null';
-
-        $qb->expr()->willReturn($expr);
-        $expr->isNotNull(sprintf('%s.%s', $this->dqlAlias, $this->field))->willReturn($expression);
-
-        $this->getFilter($qb, null)->shouldReturn($expression);
+        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Base\FilterInterface');
     }
 
-    function it_uses_dql_alias_if_passed(QueryBuilder $qb, Expr $expr)
+    function it_has_field_name()
     {
-        $dqlAlias='x';
-        $this->beConstructedWith($this->field, null);
-        $qb->expr()->willReturn($expr);
-
-        $expr->isNotNull(sprintf('%s.%s', $dqlAlias, $this->field))->shouldBeCalled();
-        $this->getFilter($qb, $dqlAlias);
+        $this->getField()->shouldReturn('field');
     }
 }
diff --git a/spec/Happyr/DoctrineSpecification/Filter/IsNullSpec.php b/spec/Happyr/DoctrineSpecification/Filter/IsNullSpec.php
index 74de981a..be0c22ca 100644
--- a/spec/Happyr/DoctrineSpecification/Filter/IsNullSpec.php
+++ b/spec/Happyr/DoctrineSpecification/Filter/IsNullSpec.php
@@ -2,51 +2,26 @@
 
 namespace spec\Happyr\DoctrineSpecification\Filter;
 
-use Doctrine\ORM\Query\Expr;
-use Doctrine\ORM\QueryBuilder;
 use Happyr\DoctrineSpecification\Filter\IsNull;
 use PhpSpec\ObjectBehavior;
-use Prophecy\Argument;
 
 /**
  * @mixin IsNull
  */
 class IsNullSpec extends ObjectBehavior
 {
-    private $field='foobar';
-
-    private $dqlAlias = 'a';
-
     function let()
     {
-        $this->beConstructedWith($this->field, $this->dqlAlias);
-    }
-
-    function it_is_an_expression()
-    {
-        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Filter');
+        $this->beConstructedWith('field');
     }
 
-    /**
-     * returns expression func object
-     */
-    function it_calls_null(QueryBuilder $qb, Expr $expr)
+    function it_is_a_filter()
     {
-        $expression = 'a.foobar is null';
-
-        $qb->expr()->willReturn($expr);
-        $expr->isNull(sprintf('%s.%s', $this->dqlAlias, $this->field))->willReturn($expression);
-
-        $this->getFilter($qb, 'b')->shouldReturn($expression);
+        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Base\FilterInterface');
     }
 
-    function it_uses_dql_alias_if_passed(QueryBuilder $qb, Expr $expr)
+    function it_has_field_name()
     {
-        $dqlAlias = 'x';
-        $this->beConstructedWith($this->field, null);
-        $qb->expr()->willReturn($expr);
-
-        $expr->isNull(sprintf('%s.%s', $dqlAlias, $this->field))->shouldBeCalled();
-        $this->getFilter($qb, $dqlAlias);
+        $this->getField()->shouldReturn('field');
     }
 }
diff --git a/spec/Happyr/DoctrineSpecification/Filter/LessOrEqualThanSpec.php b/spec/Happyr/DoctrineSpecification/Filter/LessOrEqualThanSpec.php
new file mode 100644
index 00000000..74dd0ff4
--- /dev/null
+++ b/spec/Happyr/DoctrineSpecification/Filter/LessOrEqualThanSpec.php
@@ -0,0 +1,30 @@
+<?php
+
+
+namespace spec\Happyr\DoctrineSpecification\Filter;
+
+use PhpSpec\ObjectBehavior;
+use Prophecy\Argument;
+
+class LessOrEqualThanSpec extends ObjectBehavior
+{
+    function let()
+    {
+        $this->beConstructedWith('field', 'value');
+    }
+
+    function it_is_a_filter()
+    {
+        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Base\FilterInterface');
+    }
+
+    function it_has_field_name()
+    {
+        $this->getField()->shouldReturn('field');
+    }
+
+    function it_has_field_value()
+    {
+        $this->getValue()->shouldReturn('value');
+    }
+}
diff --git a/spec/Happyr/DoctrineSpecification/Filter/LessThanSpec.php b/spec/Happyr/DoctrineSpecification/Filter/LessThanSpec.php
new file mode 100644
index 00000000..b034a40f
--- /dev/null
+++ b/spec/Happyr/DoctrineSpecification/Filter/LessThanSpec.php
@@ -0,0 +1,30 @@
+<?php
+
+
+namespace spec\Happyr\DoctrineSpecification\Filter;
+
+use PhpSpec\ObjectBehavior;
+use Prophecy\Argument;
+
+class LessThanSpec extends ObjectBehavior
+{
+    function let()
+    {
+        $this->beConstructedWith('field', 'value');
+    }
+
+    function it_is_a_filter()
+    {
+        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Base\FilterInterface');
+    }
+
+    function it_has_field_name()
+    {
+        $this->getField()->shouldReturn('field');
+    }
+
+    function it_has_field_value()
+    {
+        $this->getValue()->shouldReturn('value');
+    }
+}
diff --git a/spec/Happyr/DoctrineSpecification/Filter/LikeSpec.php b/spec/Happyr/DoctrineSpecification/Filter/LikeSpec.php
index 1b237c21..eb7be5a1 100644
--- a/spec/Happyr/DoctrineSpecification/Filter/LikeSpec.php
+++ b/spec/Happyr/DoctrineSpecification/Filter/LikeSpec.php
@@ -11,50 +11,28 @@
 
 class LikeSpec extends ObjectBehavior
 {
-    private $field = "foo";
-
-    private $value = "bar";
-
-    public function let()
+    function let()
     {
-        $this->beConstructedWith($this->field, $this->value, Like::CONTAINS, "dqlAlias");
+        $this->beConstructedWith('field', 'value', Like::CONTAINS);
     }
 
-    public function it_is_a_specification()
+    function it_is_a_filter()
     {
-        $this->shouldHaveType('Happyr\DoctrineSpecification\Specification');
+        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Base\FilterInterface');
     }
 
-    public function it_surrounds_with_wildcards_when_using_contains(QueryBuilder $qb, ArrayCollection $parameters)
+    function it_has_field_name()
     {
-        $this->beConstructedWith($this->field, $this->value, Like::CONTAINS, "dqlAlias");
-        $qb->getParameters()->willReturn($parameters);
-        $parameters->count()->willReturn(1);
-
-        $qb->setParameter("comparison_1", "%bar%")->shouldBeCalled();
-
-        $this->match($qb, null);
+        $this->getField()->shouldReturn('field');
     }
 
-    public function it_starts_with_wildcard_when_using_ends_with(QueryBuilder $qb, ArrayCollection $parameters)
+    function it_has_field_value()
     {
-        $this->beConstructedWith($this->field, $this->value, Like::ENDS_WITH, "dqlAlias");
-        $qb->getParameters()->willReturn($parameters);
-        $parameters->count()->willReturn(1);
-
-        $qb->setParameter("comparison_1", "%bar")->shouldBeCalled();
-
-        $this->match($qb, null);
+        $this->getValue()->shouldReturn('value');
     }
 
-    public function it_ends_with_wildcard_when_using_starts_with(QueryBuilder $qb, ArrayCollection $parameters)
+    function it_has_format()
     {
-        $this->beConstructedWith($this->field, $this->value, Like::STARTS_WITH, "dqlAlias");
-        $qb->getParameters()->willReturn($parameters);
-        $parameters->count()->willReturn(1);
-
-        $qb->setParameter("comparison_1", "bar%")->shouldBeCalled();
-
-        $this->match($qb, null);
+        $this->getFormat()->shouldReturn(Like::CONTAINS);
     }
-} 
+}
diff --git a/spec/Happyr/DoctrineSpecification/Filter/NotEqualsSpec.php b/spec/Happyr/DoctrineSpecification/Filter/NotEqualsSpec.php
new file mode 100644
index 00000000..3dbb7838
--- /dev/null
+++ b/spec/Happyr/DoctrineSpecification/Filter/NotEqualsSpec.php
@@ -0,0 +1,30 @@
+<?php
+
+
+namespace spec\Happyr\DoctrineSpecification\Filter;
+
+use PhpSpec\ObjectBehavior;
+use Prophecy\Argument;
+
+class NotEqualsSpec extends ObjectBehavior
+{
+    function let()
+    {
+        $this->beConstructedWith('field', 'value');
+    }
+
+    function it_is_a_filter()
+    {
+        $this->shouldBeAnInstanceOf('Happyr\DoctrineSpecification\Filter\Base\FilterInterface');
+    }
+
+    function it_has_field_name()
+    {
+        $this->getField()->shouldReturn('field');
+    }
+
+    function it_has_field_value()
+    {
+        $this->getValue()->shouldReturn('value');
+    }
+}
diff --git a/spec/Happyr/DoctrineSpecification/Logic/LogicXSpec.php b/spec/Happyr/DoctrineSpecification/Logic/LogicXSpec.php
deleted file mode 100644
index f506b56d..00000000
--- a/spec/Happyr/DoctrineSpecification/Logic/LogicXSpec.php
+++ /dev/null
@@ -1,67 +0,0 @@
-<?php
-
-namespace spec\Happyr\DoctrineSpecification\Logic;
-
-use Doctrine\ORM\Query\Expr;
-use Doctrine\ORM\QueryBuilder;
-use Happyr\DoctrineSpecification\Filter\Filter;
-use Happyr\DoctrineSpecification\Logic\LogicX;
-use Happyr\DoctrineSpecification\Specification;
-use PhpSpec\ObjectBehavior;
-use Prophecy\Argument;
-
-/**
- * @mixin LogicX
- */
-class LogicXSpec extends ObjectBehavior
-{
-    const EXPRESSION = 'andX';
-
-    function let(Specification $specificationA, Specification $specificationB)
-    {
-        $this->beConstructedWith(self::EXPRESSION, array($specificationA, $specificationB));
-    }
-
-    function it_is_a_specification()
-    {
-        $this->shouldHaveType('Happyr\DoctrineSpecification\Specification');
-    }
-
-    function it_modifies_all_child_queries(QueryBuilder $queryBuilder, Specification $specificationA, Specification $specificationB)
-    {
-        $dqlAlias = 'a';
-
-        $specificationA->modify($queryBuilder, $dqlAlias)->shouldBeCalled();
-        $specificationB->modify($queryBuilder, $dqlAlias)->shouldBeCalled();
-
-        $this->modify($queryBuilder, $dqlAlias);
-    }
-
-    function it_composes_and_child_with_expression(QueryBuilder $qb, Expr $expression, Specification $specificationA, Specification $specificationB, $x, $y)
-    {
-        $dqlAlias = 'a';
-
-        $specificationA->getFilter($qb, $dqlAlias)->willReturn($x);
-        $specificationB->getFilter($qb, $dqlAlias)->willReturn($y);
-        $qb->expr()->willReturn($expression);
-
-        $expression->{self::EXPRESSION}($x, $y)->shouldBeCalled();
-
-        $this->getFilter($qb, $dqlAlias);
-    }
-
-    function it_supports_expressions(QueryBuilder $qb, Expr $expression, Filter $exprA, Filter $exprB, $x, $y)
-    {
-        $this->beConstructedWith(self::EXPRESSION, array($exprA, $exprB));
-
-        $dqlAlias = 'a';
-
-        $exprA->getFilter($qb, $dqlAlias)->willReturn($x);
-        $exprB->getFilter($qb, $dqlAlias)->willReturn($y);
-        $qb->expr()->willReturn($expression);
-
-        $expression->{self::EXPRESSION}($x, $y)->shouldBeCalled();
-
-        $this->getFilter($qb, $dqlAlias);
-    }
-}
diff --git a/spec/Happyr/DoctrineSpecification/Logic/NotSpec.php b/spec/Happyr/DoctrineSpecification/Logic/NotSpec.php
index 6c21f38f..72665b25 100644
--- a/spec/Happyr/DoctrineSpecification/Logic/NotSpec.php
+++ b/spec/Happyr/DoctrineSpecification/Logic/NotSpec.php
@@ -3,11 +3,8 @@
 namespace spec\Happyr\DoctrineSpecification\Logic;
 
 use Doctrine\ORM\Query\Expr;
-use Doctrine\ORM\QueryBuilder;
 use Happyr\DoctrineSpecification\Filter\Filter;
 use Happyr\DoctrineSpecification\Logic\Not;
-use Happyr\DoctrineSpecification\Spec;
-use Happyr\DoctrineSpecification\Specification;
 use PhpSpec\ObjectBehavior;
 use Prophecy\Argument;
 
@@ -21,36 +18,8 @@ function let(Filter $filterExpr)
         $this->beConstructedWith($filterExpr, null);
     }
 
-    /**
-     * calls parent
-     */
-    function it_calls_parent_match(QueryBuilder $qb, Expr $expr, Filter $filterExpr)
-    {
-        $dqlAlias = 'a';
-        $expression = 'expression';
-        $parentExpression = 'foobar';
-
-        $qb->expr()->willReturn($expr);
-        $filterExpr->getFilter($qb, $dqlAlias)->willReturn($parentExpression);
-
-        $expr->not($parentExpression)->willReturn($expression);
-
-        $this->getFilter($qb, $dqlAlias)->shouldReturn($expression);
-    }
-
-    /**
-     * modifies parent query
-     */
-    function it_modifies_parent_query(QueryBuilder $qb, Specification $spec)
-    {
-        $this->beConstructedWith($spec, null);
-
-        $spec->modify($qb, 'a')->shouldBeCalled();
-        $this->modify($qb, 'a');
-    }
-
-    function it_does_not_modify_parent_query(QueryBuilder $qb)
-    {
-        $this->modify($qb, 'a');
-    }
+//    function it_is_a_specification()
+//    {
+//        $this->shouldHaveType('Happyr\DoctrineSpecification\Specification');
+//    }
 }
diff --git a/spec/Happyr/DoctrineSpecification/ParametersBagSpec.php b/spec/Happyr/DoctrineSpecification/ParametersBagSpec.php
new file mode 100644
index 00000000..4e83b85d
--- /dev/null
+++ b/spec/Happyr/DoctrineSpecification/ParametersBagSpec.php
@@ -0,0 +1,43 @@
+<?php
+
+
+namespace spec\Happyr\DoctrineSpecification;
+
+use Happyr\DoctrineSpecification\ParametersBag;
+use PhpSpec\ObjectBehavior;
+use Prophecy\Argument;
+
+/**
+ * Class ParametersBagSpec
+ * @mixin ParametersBag
+ */
+class ParametersBagSpec extends ObjectBehavior
+{
+    function it_keep_parameters()
+    {
+        $this->add('value');
+        $this->getLastName()->shouldReturn('?1');
+        $this->add('value2');
+        $this->getLastName()->shouldReturn('?2');
+    }
+
+    function it_can_hold_parameters()
+    {
+        $this->hasAny()->shouldReturn(false);
+        $this->add('value');
+        $this->hasAny()->shouldReturn(true);
+    }
+
+    function it_should_be_able_to_reset_itself()
+    {
+        $this->add('value');
+        $this->clearAll();
+        $this->hasAny()->shouldReturn(false);
+    }
+
+    function it_should_return_values()
+    {
+        $this->add('value');
+        $this->getAll()->shouldReturn([1 => 'value']);
+    }
+}
diff --git a/spec/Happyr/DoctrineSpecification/SpecSpec.php b/spec/Happyr/DoctrineSpecification/SpecSpec.php
deleted file mode 100644
index aed42ef3..00000000
--- a/spec/Happyr/DoctrineSpecification/SpecSpec.php
+++ /dev/null
@@ -1,18 +0,0 @@
-<?php
-
-namespace spec\Happyr\DoctrineSpecification;
-
-use Happyr\DoctrineSpecification\Spec;
-use PhpSpec\ObjectBehavior;
-use Prophecy\Argument;
-
-/**
- * @mixin Spec
- */
-class SpecSpec extends ObjectBehavior
-{
-    function it_creates_an_x_specification()
-    {
-        $this->andX()->shouldReturnAnInstanceOf('Happyr\DoctrineSpecification\Logic\LogicX');
-    }
-}
diff --git a/src/BaseSpecification.php b/src/BaseSpecification.php
deleted file mode 100644
index fdd54cf2..00000000
--- a/src/BaseSpecification.php
+++ /dev/null
@@ -1,122 +0,0 @@
-<?php
-
-namespace Happyr\DoctrineSpecification;
-
-use Doctrine\ORM\QueryBuilder;
-use Happyr\DoctrineSpecification\Exception\LogicException;
-use Happyr\DoctrineSpecification\Filter\Filter;
-use Happyr\DoctrineSpecification\Query\QueryModifier;
-
-/**
- * Extend this abstract class if you want to build a new spec with your domain logic
- */
-abstract class BaseSpecification implements Specification
-{
-    /**
-     * @var string|null dqlAlias
-     */
-    private $dqlAlias = null;
-
-    /**
-     * You may assign a Specification to this property. If you do, you do not *need* to overwrite the getFilterInstance
-     * or getQueryModifierInstance
-     *
-     * @var Specification spec
-     */
-    protected $spec = null;
-
-    /**
-     * @param string $dqlAlias
-     */
-    public function __construct($dqlAlias = null)
-    {
-        $this->dqlAlias = $dqlAlias;
-    }
-
-    /**
-     * This method should return a Filter. You should overwrite this if you're not using BaseSpecification::$spec
-     *
-     * @return Filter
-     */
-    protected function getFilterInstance()
-    {
-        return $this->spec;
-    }
-
-    /**
-     * This method should return a QueryModifier. You should overwrite this if you're not using BaseSpecification::$spec
-     *
-     * @return QueryModifier
-     */
-    protected function getQueryModifierInstance()
-    {
-        return $this->spec;
-    }
-
-    /**
-     * @param QueryBuilder $qb
-     * @param string       $dqlAlias
-     *
-     * @return string
-     */
-    public function getFilter(QueryBuilder $qb, $dqlAlias)
-    {
-        $this->validate('getFilterInstance', 'Happyr\DoctrineSpecification\Filter\Filter');
-
-        if (null === $filter = $this->getFilterInstance()) {
-            return;
-        }
-
-        return $filter->getFilter($qb, $this->getAlias($dqlAlias));
-    }
-
-    /**
-     * @param QueryBuilder $qb
-     * @param string       $dqlAlias
-     */
-    public function modify(QueryBuilder $qb, $dqlAlias)
-    {
-        $this->validate('getQueryModifierInstance', 'Happyr\DoctrineSpecification\Query\QueryModifier');
-
-        if (null === $queryModifier = $this->getQueryModifierInstance()) {
-            return;
-        }
-
-        $queryModifier->modify($qb, $this->getAlias($dqlAlias));
-    }
-
-    /**
-     * @param string $getter
-     * @param string $class
-     *
-     * @throws LogicException
-     */
-    private function validate($getter, $class)
-    {
-        $object = $this->$getter();
-        // if $object is an object but not instance of $class
-        if (!is_null($object) && !is_a($object, $class)) {
-            throw new LogicException(sprintf(
-                'Returned object must be an instance of %s. Please validate the %s::%s function and make it return instance of %s.',
-                $class,
-                get_class($this),
-                $getter,
-                $class
-            ));
-        }
-    }
-
-    /**
-     * @param string $dqlAlias
-     *
-     * @return string
-     */
-    private function getAlias($dqlAlias)
-    {
-        if ($this->dqlAlias !== null) {
-            return $this->dqlAlias;
-        }
-
-        return $dqlAlias;
-    }
-}
\ No newline at end of file
diff --git a/src/DoctrineTransformer.php b/src/DoctrineTransformer.php
new file mode 100644
index 00000000..b2eb4170
--- /dev/null
+++ b/src/DoctrineTransformer.php
@@ -0,0 +1,211 @@
+<?php
+
+namespace Happyr\DoctrineSpecification;
+
+use Doctrine\ORM\Query\Expr;
+use Doctrine\ORM\QueryBuilder;
+use Happyr\DoctrineSpecification\Exception\InvalidArgumentException;
+use Happyr\DoctrineSpecification\Filter\Base\FilterInterface;
+use Happyr\DoctrineSpecification\Filter\Equals;
+use Happyr\DoctrineSpecification\Filter\GreaterOrEqualThan;
+use Happyr\DoctrineSpecification\Filter\GreaterThan;
+use Happyr\DoctrineSpecification\Filter\In;
+use Happyr\DoctrineSpecification\Filter\IsNotNull;
+use Happyr\DoctrineSpecification\Filter\IsNull;
+use Happyr\DoctrineSpecification\Filter\LessOrEqualThan;
+use Happyr\DoctrineSpecification\Filter\LessThan;
+use Happyr\DoctrineSpecification\Filter\Like;
+use Happyr\DoctrineSpecification\Filter\NotEquals;
+use Happyr\DoctrineSpecification\Logic\AndX;
+use Happyr\DoctrineSpecification\Logic\Not;
+use Happyr\DoctrineSpecification\Logic\OrX;
+
+class DoctrineTransformer
+{
+    /**
+     * @var QueryBuilder
+     */
+    private $queryBuilder;
+
+    public function __construct(QueryBuilder $queryBuilder)
+    {
+        $this->queryBuilder = $queryBuilder;
+        $this->expression = $this->queryBuilder->expr();
+    }
+
+    /**
+     * Modify query builder according to specification
+     *
+     * @param FilterInterface $specification
+     * @return QueryBuilder modified query builder
+     */
+    public function getQueryBuilder(FilterInterface $specification)
+    {
+        $parameters = new ParametersBag();
+        $queryBuilder = clone $this->queryBuilder;
+
+        $result = $this->getDQLPart($specification->getFilter(), $parameters);
+        $queryBuilder->add('where', $result);
+
+        return $queryBuilder;
+    }
+
+    /**
+     * Transform specification to DQL part
+     *
+     * @param FilterInterface $specification
+     * @param ParametersBag $parameters
+     * @return QueryBuilder modified query builder
+     */
+    public function getDQLPart(FilterInterface $specification, ParametersBag $parameters)
+    {
+        return $this->getFilterDqlPart($specification, $parameters);
+    }
+
+    private function getFilterDqlPart(FilterInterface $specification, ParametersBag $parameters)
+    {
+        switch (get_class($specification)) {
+            case 'Happyr\DoctrineSpecification\Filter\Equals':
+
+                return $this->getDqlFromEquals($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Filter\GreaterOrEqualThan':
+
+                return $this->getDqlFromGreaterOrEqualThan($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Filter\GreaterThan':
+
+                return $this->getDqlFromGreaterThan($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Filter\In':
+
+                return $this->getDqlFromIn($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Filter\IsNotNull':
+
+                return $this->getDqlFromIsNotNull($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Filter\IsNull':
+
+                return $this->getDqlFromIsNull($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Filter\LessOrEqualThan':
+                return $this->getDqlFromLessOrEqualThan($specification, $parameters);
+
+            case 'Happyr\DoctrineSpecification\Filter\LessThan':
+
+                return $this->getDqlFromLessThan($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Filter\Like':
+
+                return $this->getDqlFromLike($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Filter\NotEquals':
+
+                return $this->getDqlFromNotEquals($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Logic\AndX':
+
+                return $this->getDqlFromAndX($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Logic\Not':
+
+                return $this->getDqlFromNot($specification, $parameters);
+            case 'Happyr\DoctrineSpecification\Logic\OrX':
+
+                return $this->getDqlFromOrX($specification, $parameters);
+            default:
+                throw new InvalidArgumentException(sprintf("Specification %s is not supported", get_class($specification)));
+        }
+    }
+
+    private function getDqlFromIsNotNull(IsNotNull $filter)
+    {
+        return (string)($this->expression->isNotNull($filter->getField()));
+    }
+
+    private function getDqlFromIsNull(IsNull $filter)
+    {
+        return (string)($this->expression->isNull($filter->getField()));
+    }
+
+    private function getDqlFromEquals(Equals $filter, ParametersBag $parameters)
+    {
+        $parameters->add($filter->getValue());
+
+        return (string)($this->expression->eq($filter->getField(), $parameters->getLastName()));
+    }
+
+    private function getDqlFromGreaterOrEqualThan(GreaterOrEqualThan $filter, ParametersBag $parameters)
+    {
+        $parameters->add($filter->getValue());
+
+        return (string)($this->expression->gte($filter->getField(), $parameters->getLastName()));
+    }
+
+    private function getDqlFromNotEquals(NotEquals $filter, ParametersBag $parameters)
+    {
+        $parameters->add($filter->getValue());
+
+        return (string)($this->expression->neq($filter->getField(), $parameters->getLastName()));
+    }
+
+    private function getDqlFromGreaterThan(GreaterThan $filter, ParametersBag $parameters)
+    {
+        $parameters->add($filter->getValue());
+
+        return (string)($this->expression->gt($filter->getField(), $parameters->getLastName()));
+    }
+
+    private function getDqlFromLessOrEqualThan(LessOrEqualThan $filter, ParametersBag $parameters)
+    {
+        $parameters->add($filter->getValue());
+
+        return (string)($this->expression->lte($filter->getField(), $parameters->getLastName()));
+    }
+
+    private function getDqlFromLessThan(LessThan $filter, ParametersBag $parameters)
+    {
+        $parameters->add($filter->getValue());
+
+        return (string)($this->expression->lt($filter->getField(), $parameters->getLastName()));
+    }
+
+    private function getDqlFromIn(In $filter, ParametersBag $parameters)
+    {
+        $parameters->add($filter->getValue());
+
+        return (string)($this->expression->in($filter->getField(), $parameters->getLastName()));
+    }
+
+    private function getDqlFromLike(Like $filter, ParametersBag $parameters)
+    {
+        /** @var $filter Like */
+        $format = $filter->getFormat();
+        $value = null;
+        if (Like::CONTAINS === $format) {
+            $value = "%" . $filter->getValue() . "%";
+        } elseif (Like::STARTS_WITH === $format) {
+            $value = "%" . $filter->getValue();
+        } elseif (Like::ENDS_WITH === $format) {
+            $value = $filter->getValue() . "%";
+        } else {
+            throw new InvalidArgumentException(sprintf("Unsupported filter like format %s.", $format));
+        }
+        $parameters->add($value);
+
+        return (string)($this->expression->like($filter->getField(), $parameters->getLastName()));
+    }
+
+    private function getDqlFromNot(Not $logic, ParametersBag $parameters)
+    {
+        $restriction = $this->getDQLPart($logic->getExpression(), $parameters);
+        return $this->expression->not($restriction);
+    }
+
+    private function getDqlFromAndX(AndX $logic, ParametersBag $parameters)
+    {
+        $left = $this->getDQLPart($logic->getLeft(), $parameters);
+        $right = $this->getDQLPart($logic->getRight(), $parameters);
+
+        return $this->expression->andX($left, $right);
+    }
+
+    private function getDqlFromOrX(OrX $logic, ParametersBag $parameters)
+    {
+        $left = $this->getDQLPart($logic->getLeft(), $parameters);
+        $right = $this->getDQLPart($logic->getRight(), $parameters);
+
+        return $this->expression->orX($left, $right);
+    }
+}
diff --git a/src/EntitySpecificationRepository.php b/src/EntitySpecificationRepository.php
deleted file mode 100644
index e7db8f8f..00000000
--- a/src/EntitySpecificationRepository.php
+++ /dev/null
@@ -1,32 +0,0 @@
-<?php
-
-namespace Happyr\DoctrineSpecification;
-
-use Doctrine\ORM\EntityRepository;
-
-class EntitySpecificationRepository extends EntityRepository
-{
-    private $alias = 'e';
-
-    /**
-     * Get result when you match with a Specification
-     *
-     * @param Specification   $specification
-     * @param Result\ResultModifier $modifier
-     *
-     * @return mixed
-     */
-    public function match(Specification $specification, Result\ResultModifier $modifier = null)
-    {
-        $qb = $this->createQueryBuilder($this->alias);
-
-        $specification->modify($qb, $this->alias);
-        $query = $qb->where($specification->getFilter($qb, $this->alias))->getQuery();
-
-        if ($modifier instanceof Result\ResultModifier) {
-            $modifier->modify($query);
-        }
-
-        return $query->execute();
-    }
-}
diff --git a/src/Filter/Base/Comparison.php b/src/Filter/Base/Comparison.php
new file mode 100644
index 00000000..172b5ab1
--- /dev/null
+++ b/src/Filter/Base/Comparison.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace Happyr\DoctrineSpecification\Filter\Base;
+
+abstract class Comparison extends Filter
+{
+    /**
+     * @var mixed value
+     */
+    protected $value;
+
+    /**
+     * @param string $field
+     * @param mixed  $value
+     */
+    public function __construct($field, $value)
+    {
+        $this->field = $field;
+        $this->value = $value;
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function getValue()
+    {
+        return $this->value;
+    }
+}
diff --git a/src/Filter/Base/Filter.php b/src/Filter/Base/Filter.php
new file mode 100644
index 00000000..c999a292
--- /dev/null
+++ b/src/Filter/Base/Filter.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace Happyr\DoctrineSpecification\Filter\Base;
+
+abstract class Filter implements FilterInterface
+{
+    /**
+     * @var string field
+     */
+    protected $field;
+
+    /**
+     * @param string $field
+     */
+    public function __construct($field)
+    {
+        $this->field = $field;
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function getField()
+    {
+        return $this->field;
+    }
+}
diff --git a/src/Filter/Base/FilterInterface.php b/src/Filter/Base/FilterInterface.php
new file mode 100644
index 00000000..c7bed9d2
--- /dev/null
+++ b/src/Filter/Base/FilterInterface.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Happyr\DoctrineSpecification\Filter\Base;
+
+interface FilterInterface
+{
+    /**
+     * @return mixed Return field name to filter
+     */
+    public function getField();
+}
diff --git a/src/Filter/Comparison.php b/src/Filter/Comparison.php
deleted file mode 100644
index 3495b703..00000000
--- a/src/Filter/Comparison.php
+++ /dev/null
@@ -1,113 +0,0 @@
-<?php
-
-namespace Happyr\DoctrineSpecification\Filter;
-
-use Doctrine\ORM\QueryBuilder;
-use Doctrine\ORM\Query\Expr\Comparison as DoctrineComparison;
-use Happyr\DoctrineSpecification\Exception\InvalidArgumentException;
-
-/**
- * Comparison class
- *
- * This is used when you need to compare two values
- */
-class Comparison implements Filter
-{
-    const EQ = '=';
-    const NEQ = '<>';
-    const LT = '<';
-    const LTE = '<=';
-    const GT = '>';
-    const GTE = '>=';
-    const LIKE = 'LIKE';
-
-    private static $operators = array(
-        self::EQ, self::NEQ,
-        self::LT, self::LTE,
-        self::GT, self::GTE,
-        self::LIKE
-    );
-
-    /**
-     * @var string field
-     *
-     */
-    protected $field;
-
-    /**
-     * @var string value
-     *
-     */
-    protected $value;
-
-    /**
-     * @var string dqlAlias
-     *
-     */
-    protected $dqlAlias;
-    /**
-     * @var string
-     */
-    private $operator;
-
-    /**
-     * Make sure the $field has a value equals to $value
-     *
-     * @param string $operator
-     * @param string $field
-     * @param string $value
-     * @param string $dqlAlias
-     *
-     * @throws InvalidArgumentException
-     */
-    public function __construct($operator, $field, $value, $dqlAlias = null)
-    {
-        if (!in_array($operator, self::$operators)) {
-            throw new InvalidArgumentException(
-                sprintf('"%s" is not a valid comparison operator. Valid operators are: "%s"',
-                        $operator,
-                        implode(', ', self::$operators)
-                )
-            );
-        }
-
-        $this->operator = $operator;
-        $this->field = $field;
-        $this->value = $value;
-        $this->dqlAlias = $dqlAlias;
-    }
-
-    /**
-     * @param QueryBuilder $qb
-     * @param string       $dqlAlias
-     *
-     * @return string
-     */
-    public function getFilter(QueryBuilder $qb, $dqlAlias)
-    {
-        if ($this->dqlAlias !== null) {
-            $dqlAlias = $this->dqlAlias;
-        }
-
-        $paramName = $this->getParameterName($qb);
-        $qb->setParameter($paramName, $this->value);
-
-        return (string) new DoctrineComparison(
-            sprintf('%s.%s', $dqlAlias, $this->field),
-            $this->operator,
-            sprintf(':%s', $paramName)
-        );
-    }
-
-    /**
-     * Get a good unique parameter name
-     *
-     * @param QueryBuilder $qb
-     *
-     * @return string
-     */
-    protected function getParameterName(QueryBuilder $qb)
-    {
-        return sprintf('comparison_%d', $qb->getParameters()->count());
-    }
-}
diff --git a/src/Filter/Equals.php b/src/Filter/Equals.php
index 4daeee91..fb56a89e 100644
--- a/src/Filter/Equals.php
+++ b/src/Filter/Equals.php
@@ -2,10 +2,8 @@
 
 namespace Happyr\DoctrineSpecification\Filter;
 
+use Happyr\DoctrineSpecification\Filter\Base\Comparison;
+
 class Equals extends Comparison
 {
-    public function __construct($field, $value, $dqlAlias = null)
-    {
-        parent::__construct(self::EQ, $field, $value, $dqlAlias);
-    }
 }
diff --git a/src/Filter/Filter.php b/src/Filter/Filter.php
deleted file mode 100644
index c0d8f7ce..00000000
--- a/src/Filter/Filter.php
+++ /dev/null
@@ -1,16 +0,0 @@
-<?php
-
-namespace Happyr\DoctrineSpecification\Filter;
-
-use Doctrine\ORM\QueryBuilder;
-
-interface Filter
-{
-    /**
-     * @param QueryBuilder $qb
-     * @param string       $dqlAlias
-     *
-     * @return string
-     */
-    public function getFilter(QueryBuilder $qb, $dqlAlias);
-} 
diff --git a/src/Filter/GreaterOrEqualThan.php b/src/Filter/GreaterOrEqualThan.php
index 7468c50e..3672e98e 100644
--- a/src/Filter/GreaterOrEqualThan.php
+++ b/src/Filter/GreaterOrEqualThan.php
@@ -2,10 +2,8 @@
 
 namespace Happyr\DoctrineSpecification\Filter;
 
+use Happyr\DoctrineSpecification\Filter\Base\Comparison;
+
 class GreaterOrEqualThan extends Comparison
 {
-    public function __construct($field, $value, $dqlAlias = null)
-    {
-        parent::__construct(self::GTE, $field, $value, $dqlAlias);
-    }
 }
diff --git a/src/Filter/GreaterThan.php b/src/Filter/GreaterThan.php
index 4ba20345..53b251a1 100644
--- a/src/Filter/GreaterThan.php
+++ b/src/Filter/GreaterThan.php
@@ -2,10 +2,8 @@
 
 namespace Happyr\DoctrineSpecification\Filter;
 
+use Happyr\DoctrineSpecification\Filter\Base\Comparison;
+
 class GreaterThan extends Comparison
 {
-    public function __construct($field, $value, $dqlAlias = null)
-    {
-        parent::__construct(self::GT, $field, $value, $dqlAlias);
-    }
 }
diff --git a/src/Filter/In.php b/src/Filter/In.php
index 270d07f4..5efb70c9 100644
--- a/src/Filter/In.php
+++ b/src/Filter/In.php
@@ -2,70 +2,8 @@
 
 namespace Happyr\DoctrineSpecification\Filter;
 
-use Doctrine\ORM\QueryBuilder;
+use Happyr\DoctrineSpecification\Filter\Base\Comparison;
 
-class In implements Filter
+class In extends Comparison
 {
-    /**
-     * @var string field
-     */
-    protected $field;
-
-    /**
-     * @var string value
-     */
-    protected $value;
-
-    /**
-     * @var string dqlAlias
-     */
-    protected $dqlAlias;
-
-    /**
-     * Make sure the $field has a value equals to $value
-     *
-     * @param string $field
-     * @param string $value
-     * @param string $dqlAlias
-     */
-    public function __construct($field, $value, $dqlAlias = null)
-    {
-        $this->field = $field;
-        $this->value = $value;
-        $this->dqlAlias = $dqlAlias;
-    }
-
-
-    /**
-     * @param QueryBuilder $qb
-     * @param string $dqlAlias
-     *
-     * @return string
-     */
-    public function getFilter(QueryBuilder $qb, $dqlAlias)
-    {
-        if ($this->dqlAlias !== null) {
-            $dqlAlias = $this->dqlAlias;
-        }
-
-        $paramName = $this->getParameterName($qb);
-        $qb->setParameter($paramName, $this->value);
-
-        return (string) $qb->expr()->in(
-            sprintf('%s.%s', $dqlAlias, $this->field),
-            sprintf(':%s', $paramName)
-        );
-    }
-
-    /**
-     * Get a good unique parameter name
-     *
-     * @param QueryBuilder $qb
-     *
-     * @return string
-     */
-    protected function getParameterName(QueryBuilder $qb)
-    {
-        return sprintf('in_%d', $qb->getParameters()->count());
-    }
 }
diff --git a/src/Filter/IsNotNull.php b/src/Filter/IsNotNull.php
index 1311e6f3..fbc3f27d 100644
--- a/src/Filter/IsNotNull.php
+++ b/src/Filter/IsNotNull.php
@@ -2,22 +2,8 @@
 
 namespace Happyr\DoctrineSpecification\Filter;
 
-use Doctrine\ORM\QueryBuilder;
+use Happyr\DoctrineSpecification\Filter\Base\Filter;
 
-class IsNotNull extends IsNull
+class IsNotNull extends Filter
 {
-    /**
-     * @param QueryBuilder $qb
-     * @param string $dqlAlias
-     *
-     * @return string
-     */
-    public function getFilter(QueryBuilder $qb, $dqlAlias)
-    {
-        if ($this->dqlAlias !== null) {
-            $dqlAlias = $this->dqlAlias;
-        }
-
-        return (string) $qb->expr()->isNotNull(sprintf('%s.%s', $dqlAlias, $this->field));
-    }
-}
\ No newline at end of file
+}
diff --git a/src/Filter/IsNull.php b/src/Filter/IsNull.php
index 8e6646e6..b78376c3 100644
--- a/src/Filter/IsNull.php
+++ b/src/Filter/IsNull.php
@@ -2,42 +2,8 @@
 
 namespace Happyr\DoctrineSpecification\Filter;
 
-use Doctrine\ORM\QueryBuilder;
+use Happyr\DoctrineSpecification\Filter\Base\Filter;
 
-class IsNull implements Filter
+class IsNull extends Filter
 {
-    /**
-     * @var string field
-     */
-    protected $field;
-
-    /**
-     * @var null|string dqlAlias
-     */
-    protected $dqlAlias;
-
-    /**
-     * @param string      $field
-     * @param string|null $dqlAlias
-     */
-    public function __construct($field, $dqlAlias = null)
-    {
-        $this->field = $field;
-        $this->dqlAlias = $dqlAlias;
-    }
-
-    /**
-     * @param QueryBuilder $qb
-     * @param string $dqlAlias
-     *
-     * @return string
-     */
-    public function getFilter(QueryBuilder $qb, $dqlAlias)
-    {
-        if ($this->dqlAlias !== null) {
-            $dqlAlias = $this->dqlAlias;
-        }
-
-        return (string) $qb->expr()->isNull(sprintf('%s.%s', $dqlAlias, $this->field));
-    }
 }
diff --git a/src/Filter/LessOrEqualThan.php b/src/Filter/LessOrEqualThan.php
index b479f2b9..72b203a4 100644
--- a/src/Filter/LessOrEqualThan.php
+++ b/src/Filter/LessOrEqualThan.php
@@ -2,10 +2,8 @@
 
 namespace Happyr\DoctrineSpecification\Filter;
 
+use Happyr\DoctrineSpecification\Filter\Base\Comparison;
+
 class LessOrEqualThan extends Comparison
 {
-    public function __construct($field, $value, $dqlAlias = null)
-    {
-        parent::__construct(self::LTE, $field, $value, $dqlAlias);
-    }
 }
diff --git a/src/Filter/LessThan.php b/src/Filter/LessThan.php
index 6a87a2bd..be29e044 100644
--- a/src/Filter/LessThan.php
+++ b/src/Filter/LessThan.php
@@ -2,10 +2,8 @@
 
 namespace Happyr\DoctrineSpecification\Filter;
 
+use Happyr\DoctrineSpecification\Filter\Base\Comparison;
+
 class LessThan extends Comparison
 {
-    public function __construct($field, $value, $dqlAlias = null)
-    {
-        parent::__construct(self::LT, $field, $value, $dqlAlias);
-    }
 }
diff --git a/src/Filter/Like.php b/src/Filter/Like.php
index 8fad640d..ad820a88 100644
--- a/src/Filter/Like.php
+++ b/src/Filter/Like.php
@@ -2,23 +2,30 @@
 
 namespace Happyr\DoctrineSpecification\Filter;
 
+use Happyr\DoctrineSpecification\Filter\Base\Comparison;
+
 class Like extends Comparison
 {
-    const CONTAINS = "%%%s%%";
-    const ENDS_WITH = "%%%s";
-    const STARTS_WITH = "%s%%";
+    const CONTAINS = 1;
+    const ENDS_WITH = 2;
+    const STARTS_WITH = 3;
 
-    public function __construct($field, $value, $format = self::CONTAINS, $dqlAlias = null)
+    /**
+     * @param string $field
+     * @param mixed  $value
+     * @param int    $format
+     */
+    public function __construct($field, $value, $format = self::CONTAINS)
     {
-        $formattedValue = $this->formatValue($format, $value);
-        parent::__construct(self::LIKE, $field, $formattedValue, $dqlAlias);
+        parent::__construct($field, $value);
+        $this->format = $format;
     }
 
     /**
-     * @param string $format
+     * @return int
      */
-    private function formatValue($format, $value)
+    public function getFormat()
     {
-        return sprintf($format, $value);
+        return $this->format;
     }
 }
diff --git a/src/Filter/NotEquals.php b/src/Filter/NotEquals.php
index 474b6716..dafc85be 100644
--- a/src/Filter/NotEquals.php
+++ b/src/Filter/NotEquals.php
@@ -2,10 +2,8 @@
 
 namespace Happyr\DoctrineSpecification\Filter;
 
+use Happyr\DoctrineSpecification\Filter\Base\Comparison;
+
 class NotEquals extends Comparison
 {
-    public function __construct($field, $value, $dqlAlias = null)
-    {
-        parent::__construct(self::NEQ, $field, $value, $dqlAlias);
-    }
 }
diff --git a/src/Logic/AndX.php b/src/Logic/AndX.php
index 0d48de2c..a9411a7c 100644
--- a/src/Logic/AndX.php
+++ b/src/Logic/AndX.php
@@ -2,10 +2,40 @@
 
 namespace Happyr\DoctrineSpecification\Logic;
 
-class AndX extends LogicX
+
+use Happyr\DoctrineSpecification\Filter\Base\FilterInterface;
+
+class AndX implements LogicX
 {
-    function __construct()
+    private $left;
+    private $right;
+
+    public function __construct(FilterInterface $left, FilterInterface $right)
+    {
+        $this->left = $left;
+        $this->right = $right;
+    }
+
+    /**
+     * @return mixed
+     */
+    public function getLeft()
+    {
+        return $this->left;
+    }
+
+    /**
+     * @return mixed
+     */
+    public function getRight()
+    {
+        return $this->right;
+    }
+
+    /**
+     * @return mixed Return field name to filter
+     */
+    public function getField()
     {
-        parent::__construct(self::AND_X, func_get_args());
     }
 }
diff --git a/src/Logic/LogicX.php b/src/Logic/LogicX.php
index c7e9d07c..beb3a431 100644
--- a/src/Logic/LogicX.php
+++ b/src/Logic/LogicX.php
@@ -2,69 +2,8 @@
 
 namespace Happyr\DoctrineSpecification\Logic;
 
-use Doctrine\ORM\QueryBuilder;
-use Happyr\DoctrineSpecification\Filter\Filter;
-use Happyr\DoctrineSpecification\Specification;
+use Happyr\DoctrineSpecification\Filter\Base\FilterInterface;
 
-/**
- * This class should be used when you combine two or more Expressions
- */
-class LogicX implements Specification
+interface LogicX extends FilterInterface
 {
-    const AND_X = 'andX';
-    const OR_X = 'orX';
-
-    /**
-     * @var Filter[] children
-     */
-    private $children;
-
-    /**
-     * @var string
-     */
-    private $expression;
-
-    /**
-     * Take two or more Expression as parameters
-     *
-     * @param string $expression
-     * @param Filter[] $children
-     */
-    public function __construct($expression, array $children)
-    {
-        $this->expression = $expression;
-        $this->children = $children;
-    }
-
-    /**
-     * @param QueryBuilder $qb
-     * @param string $dqlAlias
-     *
-     * @return string
-     */
-    public function getFilter(QueryBuilder $qb, $dqlAlias)
-    {
-        return call_user_func_array(
-            array($qb->expr(), $this->expression),
-            array_map(
-                function (Filter $expr) use ($qb, $dqlAlias) {
-                    return $expr->getFilter($qb, $dqlAlias);
-                },
-                $this->children
-            )
-        );
-    }
-
-    /**
-     * @param QueryBuilder $query
-     * @param string       $dqlAlias
-     */
-    public function modify(QueryBuilder $query, $dqlAlias)
-    {
-        foreach ($this->children as $child) {
-            if ($child instanceof Specification) {
-                $child->modify($query, $dqlAlias);
-            }
-        }
-    }
 }
diff --git a/src/Logic/Not.php b/src/Logic/Not.php
index 9da50f36..acdef4e4 100644
--- a/src/Logic/Not.php
+++ b/src/Logic/Not.php
@@ -2,44 +2,36 @@
 
 namespace Happyr\DoctrineSpecification\Logic;
 
-use Doctrine\ORM\QueryBuilder;
-use Happyr\DoctrineSpecification\Filter\Filter;
-use Happyr\DoctrineSpecification\Specification;
+use Happyr\DoctrineSpecification\Filter\Base\FilterInterface;
+use Happyr\DoctrineSpecification\SpecificationInterface;
 
-class Not implements Specification
+class Not implements LogicX
 {
     /**
-     * @var Filter parent
+     * @var FilterInterface
      */
-    private $parent;
+    private $expression;
 
     /**
-     * @param Filter $expr
+     * @param FilterInterface $expression
      */
-    public function __construct(Filter $expr)
+    public function __construct(FilterInterface $expression)
     {
-        $this->parent = $expr;
+        $this->expression = $expression;
     }
 
     /**
-     * @param QueryBuilder $qb
-     * @param string $dqlAlias
-     *
-     * @return string
+     * @return SpecificationInterface
      */
-    public function getFilter(QueryBuilder $qb, $dqlAlias)
+    public function getExpression()
     {
-        return (string) $qb->expr()->not($this->parent->getFilter($qb, $dqlAlias));
+        return $this->expression;
     }
 
     /**
-     * @param QueryBuilder $query
-     * @param string       $dqlAlias
+     * @return mixed Return field name to filter
      */
-    public function modify(QueryBuilder $query, $dqlAlias)
+    public function getField()
     {
-        if ($this->parent instanceof Specification) {
-            $this->parent->modify($query, $dqlAlias);
-        }
     }
 }
diff --git a/src/Logic/OrX.php b/src/Logic/OrX.php
index 13cc36c2..85fb4662 100644
--- a/src/Logic/OrX.php
+++ b/src/Logic/OrX.php
@@ -2,10 +2,39 @@
 
 namespace Happyr\DoctrineSpecification\Logic;
 
-class OrX extends LogicX
+use Happyr\DoctrineSpecification\Filter\Base\FilterInterface;
+
+class OrX implements  LogicX
 {
-    function __construct()
+    private $left;
+    private $right;
+
+    public function __construct(FilterInterface $left, FilterInterface $right)
+    {
+        $this->left = $left;
+        $this->right = $right;
+    }
+
+    /**
+     * @return mixed
+     */
+    public function getLeft()
+    {
+        return $this->left;
+    }
+
+    /**
+     * @return mixed
+     */
+    public function getRight()
+    {
+        return $this->right;
+    }
+
+    /**
+     * @return mixed Return field name to filter
+     */
+    public function getField()
     {
-        parent::__construct(self::OR_X, func_get_args());
     }
 }
diff --git a/src/ParametersBag.php b/src/ParametersBag.php
new file mode 100644
index 00000000..59fa560e
--- /dev/null
+++ b/src/ParametersBag.php
@@ -0,0 +1,67 @@
+<?php
+
+namespace Happyr\DoctrineSpecification;
+
+class ParametersBag
+{
+    /**
+     * @var array DQL Parameters array
+     */
+    private $parameters = [];
+
+    /**
+     * @var string
+     */
+    private $lastName = '';
+
+    /**
+     * Clears parameters array
+     */
+    public function clearAll()
+    {
+        $this->parameters = [];
+    }
+
+    /**
+     * Returns parameters array
+     *
+     * @return array
+     */
+    public function getAll()
+    {
+        return $this->parameters;
+    }
+
+    /**
+     * Add new parameter to collection and returns it's name
+     *
+     * @param $value mixed parameter value
+     *
+     * @return string DQL Parameter name
+     */
+    public function add($value)
+    {
+        $key = count($this->parameters) + 1;
+        $this->parameters[$key] = $value;
+
+        $this->lastName = '?' . $key;
+    }
+
+    /**
+     * Checks whether the parameters array is non empty
+     *
+     * @return bool
+     */
+    public function hasAny()
+    {
+        return (boolean)count($this->parameters);
+    }
+
+    /**
+     * @return string
+     */
+    public function getLastName()
+    {
+        return $this->lastName;
+    }
+}
diff --git a/src/Query/QueryModifier.php b/src/Query/QueryModifier.php
index 25c1ff41..615eb4cd 100644
--- a/src/Query/QueryModifier.php
+++ b/src/Query/QueryModifier.php
@@ -6,10 +6,4 @@
 
 interface QueryModifier
 {
-    /**
-     * @param QueryBuilder $qb
-     * @param string       $dqlAlias
-     * @return void
-     */
-    public function modify(QueryBuilder $qb, $dqlAlias);
-} 
+}
diff --git a/src/RepositoryFactory.php b/src/RepositoryFactory.php
deleted file mode 100644
index 1d9c209a..00000000
--- a/src/RepositoryFactory.php
+++ /dev/null
@@ -1,31 +0,0 @@
-<?php
-
-namespace Happyr\DoctrineSpecification;
-
-use Doctrine\ORM\EntityManagerInterface;
-use Doctrine\ORM\EntityRepository;
-
-/**
- * Factory class for creating EntitySpecificationRepository instances.
- *
- * Provides an implementation of RepositoryFactory so that the
- * default repository type in Doctrine can easily be replaced.
- */
-class RepositoryFactory implements \Doctrine\ORM\Repository\RepositoryFactory
-{
-    /**
-     * Gets the repository for an entity class.
-     *
-     * @param EntityManagerInterface $entityManager The EntityManager instance.
-     * @param string                 $entityName    The name of the entity.
-     *
-     * @return EntityRepository
-     */
-    public function getRepository(EntityManagerInterface $entityManager, $entityName)
-    {
-        return new EntitySpecificationRepository(
-            $entityManager,
-            $entityManager->getClassMetadata($entityName)
-        );
-    }
-}
diff --git a/src/Spec.php b/src/Spec.php
deleted file mode 100644
index b071929a..00000000
--- a/src/Spec.php
+++ /dev/null
@@ -1,95 +0,0 @@
-<?php
-
-namespace Happyr\DoctrineSpecification;
-
-use Happyr\DoctrineSpecification\Filter\Filter;
-use Happyr\DoctrineSpecification\Filter\IsNotNull;
-use Happyr\DoctrineSpecification\Result\AsArray;
-use Happyr\DoctrineSpecification\Filter\Comparison;
-use Happyr\DoctrineSpecification\Filter\In;
-use Happyr\DoctrineSpecification\Filter\Like;
-use Happyr\DoctrineSpecification\Filter\IsNull;
-use Happyr\DoctrineSpecification\Logic\LogicX;
-use Happyr\DoctrineSpecification\Logic\Not;
-use Happyr\DoctrineSpecification\Query\Join;
-
-/**
- * Factory class for the specifications
- */
-class Spec
-{
-    public static function andX()
-    {
-        return new LogicX(LogicX::AND_X, func_get_args());
-    }
-
-    public static function orX()
-    {
-        return new LogicX(LogicX::OR_X, func_get_args());
-    }
-
-    public static function join($field, $newAlias, $dqlAlias = null)
-    {
-        return new Join($field, $newAlias, $dqlAlias);
-    }
-
-    public static function asArray()
-    {
-        return new AsArray();
-    }
-
-    public static function not(Filter $spec)
-    {
-        return new Not($spec);
-    }
-
-    public static function isNull($field, $dqlAlias = null)
-    {
-        return new IsNull($field, $dqlAlias);
-    }
-
-    public static function isNotNull($field, $dqlAlias = null)
-    {
-        return new IsNotNull($field, $dqlAlias);
-    }
-
-    public static function in($field, $value, $dqlAlias = null)
-    {
-        return new In($field, $value, $dqlAlias);
-    }
-
-    public static function eq($field, $value, $dqlAlias = null)
-    {
-        return new Comparison(Comparison::EQ, $field, $value, $dqlAlias);
-    }
-
-    public static function neq($field, $value, $dqlAlias = null)
-    {
-        return new Comparison(Comparison::NEQ, $field, $value, $dqlAlias);
-    }
-
-    public static function lt($field, $value, $dqlAlias = null)
-    {
-        return new Comparison(Comparison::LT, $field, $value, $dqlAlias);
-    }
-
-    public static function lte($field, $value, $dqlAlias = null)
-    {
-        return new Comparison(Comparison::LTE, $field, $value, $dqlAlias);
-    }
-
-    public static function gt($field, $value, $dqlAlias = null)
-    {
-        return new Comparison(Comparison::GT, $field, $value, $dqlAlias);
-    }
-
-    public static function gte($field, $value, $dqlAlias = null)
-    {
-        return new Comparison(Comparison::GTE, $field, $value, $dqlAlias);
-    }
-
-    public static function like($field, $value, $format = Like::CONTAINS, $dqlAlias = null)
-    {
-        return new Like($field, $value, $format, $dqlAlias);
-    }
-}
diff --git a/src/Specification.php b/src/Specification.php
deleted file mode 100644
index dcda7e90..00000000
--- a/src/Specification.php
+++ /dev/null
@@ -1,11 +0,0 @@
-<?php
-
-namespace Happyr\DoctrineSpecification;
-
-use Happyr\DoctrineSpecification\Filter\Filter;
-use Happyr\DoctrineSpecification\Query\QueryModifier;
-
-interface Specification extends Filter, QueryModifier
-{
-
-}
diff --git a/src/SpecificationInterface.php b/src/SpecificationInterface.php
new file mode 100644
index 00000000..59861847
--- /dev/null
+++ b/src/SpecificationInterface.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Happyr\DoctrineSpecification;
+
+use Happyr\DoctrineSpecification\Filter\Filter;
+
+interface SpecificationInterface
+{
+    public function getFilter();
+}
diff --git a/src/Transformer/LogicTransformer.php b/src/Transformer/LogicTransformer.php
new file mode 100644
index 00000000..d7a19171
--- /dev/null
+++ b/src/Transformer/LogicTransformer.php
@@ -0,0 +1,62 @@
+<?php
+
+namespace Transformer;
+
+use Doctrine\ORM\Query\Expr;
+use Doctrine\ORM\QueryBuilder;
+use Happyr\DoctrineSpecification\DoctrineTransformer;
+use Happyr\DoctrineSpecification\Filter\Base\FilterInterface;
+use Happyr\DoctrineSpecification\Logic\Not;
+use Happyr\DoctrineSpecification\ParametersBag;
+use Happyr\DoctrineSpecification\Transformer\FilterTransformerInterface;
+
+class LogicTransformer implements FilterTransformerInterface
+{
+    /**
+     * @var Expr
+     */
+    private $expression;
+
+    /**
+     * @var DoctrineTransformer
+     */
+    private $rootTransformer;
+
+    /**
+     * @inheritdoc
+     */
+    public function setExpression(Expr $expression)
+    {
+        $this->expression = $expression;
+    }
+
+    public function __construct(DoctrineTransformer $rootTransformer)
+    {
+        $this->rootTransformer = $rootTransformer;
+    }
+
+    public function supports(FilterInterface $filter)
+    {
+        return $filter instanceof Not;
+    }
+
+    /**
+     * Transform filter to DQL part
+     * @param FilterInterface $filter
+     * @param ParametersBag $parameters
+     *
+     * @return string
+     */
+    public function transform(FilterInterface $filter, ParametersBag $parameters)
+    {
+        if ($filter instanceof Not) {
+            return $this->transformNot($filter);
+        }
+    }
+
+
+    private function transformNot(Not $filter)
+    {
+        return $this->expression->not($this->rootTransformer->transform($filter->getExpression()));
+    }
+}