diff --git a/benchmarks/HugeSchemaBench.php b/benchmarks/HugeSchemaBench.php
index fa26228..b9830c0 100644
--- a/benchmarks/HugeSchemaBench.php
+++ b/benchmarks/HugeSchemaBench.php
@@ -22,7 +22,7 @@ class HugeSchemaBench
     private $schemaBuilder;
 
     /**
-     * @var Schema\Descriptor
+     * @var \GraphQL\Type\Descriptor
      */
     private $descriptor;
 
@@ -47,7 +47,7 @@ class HugeSchemaBench
         $this->schema = $this->schemaBuilder->buildSchema();
 
         $queryBuilder = new QueryGenerator($this->schema, 0.05);
-        $this->descriptor = $this->schema->getDescriptor();
+        $this->descriptor = $this->schema->describe();
         $this->smallQuery = $queryBuilder->buildQuery();
     }
 
@@ -78,7 +78,7 @@ class HugeSchemaBench
     private function createLazySchema()
     {
         return new Schema(
-            Schema\Config::create()
+            \GraphQL\Config::create()
                 ->setQuery($this->schemaBuilder->buildQueryType())
                 // ->setDescriptor($this->descriptor)
                 ->setTypeLoader(function($name) {
diff --git a/src/Schema/Config.php b/src/Config.php
similarity index 71%
rename from src/Schema/Config.php
rename to src/Config.php
index c59e0b5..f908980 100644
--- a/src/Schema/Config.php
+++ b/src/Config.php
@@ -1,6 +1,8 @@
 <?php
-namespace GraphQL\Schema;
+namespace GraphQL;
 
+use GraphQL\Executor\Promise\PromiseAdapter;
+use GraphQL\Type\Descriptor;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\Type;
@@ -10,9 +12,9 @@ use GraphQL\Utils\Utils;
  * Class Config
  * Note: properties are marked as public for performance reasons. They should be considered read-only.
  *
- * @package GraphQL\Schema
+ * @package GraphQL
  */
-final class Config
+class Config
 {
     /**
      * @var ObjectType
@@ -49,6 +51,11 @@ final class Config
      */
     public $typeLoader;
 
+    /**
+     * @var PromiseAdapter
+     */
+    public $promiseAdapter;
+
     /**
      * @param array $options
      * @return Config
@@ -61,7 +68,8 @@ final class Config
             if (isset($options['query'])) {
                 Utils::invariant(
                     $options['query'] instanceof ObjectType,
-                    "Schema query must be Object Type if provided but got: " . Utils::getVariableType($options['query'])
+                    'Schema query must be Object Type if provided but got: %s',
+                    Utils::getVariableType($options['query'])
                 );
                 $config->setQuery($options['query']);
             }
@@ -69,7 +77,8 @@ final class Config
             if (isset($options['mutation'])) {
                 Utils::invariant(
                     $options['mutation'] instanceof ObjectType,
-                    "Schema mutation must be Object Type if provided but got: " . Utils::getVariableType($options['mutation'])
+                    'Schema mutation must be Object Type if provided but got: %s',
+                    Utils::getVariableType($options['mutation'])
                 );
                 $config->setMutation($options['mutation']);
             }
@@ -77,7 +86,8 @@ final class Config
             if (isset($options['subscription'])) {
                 Utils::invariant(
                     $options['subscription'] instanceof ObjectType,
-                    "Schema subscription must be Object Type if provided but got: " . Utils::getVariableType($options['subscription'])
+                    'Schema subscription must be Object Type if provided but got: %s',
+                    Utils::getVariableType($options['subscription'])
                 );
                 $config->setSubscription($options['subscription']);
             }
@@ -85,7 +95,8 @@ final class Config
             if (isset($options['types'])) {
                 Utils::invariant(
                     is_array($options['types']),
-                    "Schema types must be array if provided but got: " . Utils::getVariableType($options['types'])
+                    'Schema types must be array if provided but got: %s',
+                    Utils::getVariableType($options['types'])
                 );
                 $config->setTypes($options['types']);
             }
@@ -93,7 +104,8 @@ final class Config
             if (isset($options['directives'])) {
                 Utils::invariant(
                     is_array($options['directives']),
-                    "Schema directives must be array if provided but got: " . Utils::getVariableType($options['directives'])
+                    'Schema directives must be array if provided but got: %s',
+                    Utils::getVariableType($options['directives'])
                 );
                 $config->setDirectives($options['directives']);
             }
@@ -101,15 +113,27 @@ final class Config
             if (isset($options['typeLoader'])) {
                 Utils::invariant(
                     is_callable($options['typeLoader']),
-                    "Schema type loader must be callable if provided but got: " . Utils::getVariableType($options['typeLoader'])
+                    'Schema type loader must be callable if provided but got: %s',
+                    Utils::getVariableType($options['typeLoader'])
                 );
             }
 
             if (isset($options['descriptor'])) {
                 Utils::invariant(
                     $options['descriptor'] instanceof Descriptor,
-                    "Schema descriptor must be instance of GraphQL\\Schema\\Descriptor but got: " . Utils::getVariableType($options['descriptor'])
+                    'Schema descriptor must be instance of GraphQL\Type\Descriptor but got: %s',
+                    Utils::getVariableType($options['descriptor'])
                 );
+                $config->setDescriptor($options['descriptor']);
+            }
+
+            if (isset($options['promiseAdapter'])) {
+                Utils::invariant(
+                    $options['promiseAdapter'] instanceof PromiseAdapter,
+                    'Promise adapter must be an instance of GraphQL\Executor\Promise\PromiseAdapter but got: %s',
+                    Utils::getVariableType($options['promiseAdapter'])
+                );
+                $config->setPromiseAdapter($options['promiseAdapter']);
             }
         }
 
@@ -259,4 +283,22 @@ final class Config
         $this->typeLoader = $typeLoader;
         return $this;
     }
+
+    /**
+     * @return PromiseAdapter
+     */
+    public function getPromiseAdapter()
+    {
+        return $this->promiseAdapter;
+    }
+
+    /**
+     * @param PromiseAdapter $promiseAdapter
+     * @return Config
+     */
+    public function setPromiseAdapter($promiseAdapter)
+    {
+        $this->promiseAdapter = $promiseAdapter;
+        return $this;
+    }
 }
diff --git a/src/Error/UserError.php b/src/Error/UserError.php
index ad07ee9..8276c94 100644
--- a/src/Error/UserError.php
+++ b/src/Error/UserError.php
@@ -4,8 +4,7 @@ namespace GraphQL\Error;
 /**
  * Class UserError
  *
- * Note:
- * Error that can be display safely to client...
+ * Error that can be safely displayed to client...
  *
  * @package GraphQL\Error
  */
diff --git a/src/GraphQL.php b/src/GraphQL.php
index 4ec1e88..3417d49 100644
--- a/src/GraphQL.php
+++ b/src/GraphQL.php
@@ -16,20 +16,6 @@ use GraphQL\Validator\Rules\QueryComplexity;
 
 class GraphQL
 {
-    const WARNING_ON_IMPLEMENTATION_RESOLUTION = 1;
-
-    private static $ignoredErrors = [];
-
-    public static function setIgnoreError($errorCode, $set = true)
-    {
-        self::$ignoredErrors[$errorCode] = $set ? true : null;
-    }
-
-    public static function isIgnoredError($errorCode)
-    {
-        return isset(self::$ignoredErrors[$errorCode]);
-    }
-
     /**
      * This is the primary entry point function for fulfilling GraphQL operations
      * by parsing, validating, and executing a GraphQL document along side a
@@ -73,7 +59,7 @@ class GraphQL
         $contextValue = null,
         $variableValues = null,
         $operationName = null,
-        $fieldResolver = null
+        callable $fieldResolver = null
     )
     {
         $result = self::executeAndReturnResult(
@@ -104,6 +90,7 @@ class GraphQL
      * @param Schema $schema
      * @param string|DocumentNode $source
      * @param mixed $rootValue
+     * @param mixed $contextValue
      * @param array|null $variableValues
      * @param string|null $operationName
      * @param callable $fieldResolver
@@ -116,7 +103,7 @@ class GraphQL
         $contextValue = null,
         $variableValues = null,
         $operationName = null,
-        $fieldResolver = null
+        callable $fieldResolver = null
     )
     {
         try {
diff --git a/src/Schema.php b/src/Schema.php
index 01fc3b5..51c34bb 100644
--- a/src/Schema.php
+++ b/src/Schema.php
@@ -1,8 +1,7 @@
 <?php
 namespace GraphQL;
 
-use GraphQL\Schema\Config;
-use GraphQL\Schema\Descriptor;
+use GraphQL\Type\Descriptor;
 use GraphQL\Type\Definition\AbstractType;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\InterfaceType;
@@ -83,12 +82,13 @@ class Schema
             );
             list($queryType, $mutationType, $subscriptionType) = func_get_args() + [null, null, null];
 
-            $config = Config::create()
-                ->setQuery($queryType)
-                ->setMutation($mutationType)
-                ->setSubscription($subscriptionType)
-            ;
-        } else if (is_array($config)) {
+            $config = [
+                'query' => $queryType,
+                'mutation' => $mutationType,
+                'subscription' => $subscriptionType
+            ];
+        }
+        if (is_array($config)) {
             $config = Config::create($config);
         }
 
@@ -101,8 +101,8 @@ class Schema
                 'subscription',
                 'types',
                 'directives',
-                'descriptor',
-                'typeLoader'
+                'typeLoader',
+                'descriptor'
             ]),
             Utils::getVariableType($config)
         );
@@ -116,6 +116,8 @@ class Schema
     }
 
     /**
+     * Returns schema query type
+     *
      * @return ObjectType
      */
     public function getQueryType()
@@ -124,6 +126,8 @@ class Schema
     }
 
     /**
+     * Returns schema mutation type
+     *
      * @return ObjectType|null
      */
     public function getMutationType()
@@ -132,6 +136,8 @@ class Schema
     }
 
     /**
+     * Returns schema subscription
+     *
      * @return ObjectType|null
      */
     public function getSubscriptionType()
@@ -148,7 +154,8 @@ class Schema
     }
 
     /**
-     * Returns full map of types in this schema.
+     * Returns array of all types in this schema. Keys of this array represent type names, values are instances
+     * of corresponding type definitions
      *
      * @return Type[]
      */
@@ -156,6 +163,7 @@ class Schema
     {
         if (!$this->fullyLoaded) {
             if ($this->config->descriptor && $this->config->typeLoader) {
+                // Following is still faster than $this->collectAllTypes() because it won't init fields
                 $typesToResolve = array_diff_key($this->config->descriptor->typeMap, $this->resolvedTypes);
                 foreach ($typesToResolve as $typeName => $_) {
                     $this->resolvedTypes[$typeName] = $this->loadType($typeName);
@@ -185,22 +193,12 @@ class Schema
      *
      * @return Descriptor
      */
-    public function getDescriptor()
+    public function describe()
     {
         if ($this->descriptor) {
             return $this->descriptor;
         }
-        if ($this->config->descriptor) {
-            return $this->config->descriptor;
-        }
-        return $this->descriptor = $this->buildDescriptor();
-    }
 
-    /**
-     * @return Descriptor
-     */
-    public function buildDescriptor()
-    {
         $this->resolvedTypes = $this->collectAllTypes();
         $this->fullyLoaded = true;
 
@@ -243,6 +241,9 @@ class Schema
     }
 
     /**
+     * Returns all possible concrete types for given abstract type
+     * (implementations for interfaces and members of union type for unions)
+     *
      * @param AbstractType $abstractType
      * @return ObjectType[]
      */
@@ -253,7 +254,7 @@ class Schema
         }
 
         /** @var InterfaceType $abstractType */
-        $descriptor = $this->getDescriptor();
+        $descriptor = $this->config->descriptor ?: $this->describe();
 
         $result = [];
         if (isset($descriptor->possibleTypeMap[$abstractType->name])) {
@@ -264,6 +265,13 @@ class Schema
         return $result;
     }
 
+    /**
+     * Accepts name of type or type instance and returns type instance. If type with given name is not loaded yet -
+     * will load it first.
+     *
+     * @param $typeOrName
+     * @return Type
+     */
     public function resolveType($typeOrName)
     {
         if ($typeOrName instanceof Type) {
@@ -292,6 +300,9 @@ class Schema
     }
 
     /**
+     * Returns true if object type is concrete type of given abstract type
+     * (implementation for interfaces and members of union type for unions)
+     *
      * @param AbstractType $abstractType
      * @param ObjectType $possibleType
      * @return bool
@@ -311,6 +322,8 @@ class Schema
     }
 
     /**
+     * Returns a list of directives supported by this schema
+     *
      * @return Directive[]
      */
     public function getDirectives()
@@ -319,6 +332,8 @@ class Schema
     }
 
     /**
+     * Returns instance of directive by name
+     *
      * @param $name
      * @return Directive
      */
diff --git a/src/Schema/Descriptor.php b/src/Type/Descriptor.php
similarity index 98%
rename from src/Schema/Descriptor.php
rename to src/Type/Descriptor.php
index b41029c..39e98cf 100644
--- a/src/Schema/Descriptor.php
+++ b/src/Type/Descriptor.php
@@ -1,5 +1,5 @@
 <?php
-namespace GraphQL\Schema;
+namespace GraphQL\Type;
 
 use GraphQL\Utils\Utils;
 
diff --git a/src/Utils/MixedStore.php b/src/Utils/MixedStore.php
index 124dd70..89f183f 100644
--- a/src/Utils/MixedStore.php
+++ b/src/Utils/MixedStore.php
@@ -1,6 +1,5 @@
 <?php
 namespace GraphQL\Utils;
-use GraphQL\Utils\Utils;
 
 /**
  * Similar to PHP array, but allows any type of data to act as key (including arrays, objects, scalars)
diff --git a/src/Utils/SchemaPrinter.php b/src/Utils/SchemaPrinter.php
index 37444fe..15101bb 100644
--- a/src/Utils/SchemaPrinter.php
+++ b/src/Utils/SchemaPrinter.php
@@ -12,7 +12,6 @@ use GraphQL\Type\Definition\ScalarType;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Definition\UnionType;
 use GraphQL\Type\Definition\Directive;
-use GraphQL\Utils\Utils;
 
 /**
  * Class SchemaPrinter
diff --git a/src/Utils/TypeInfo.php b/src/Utils/TypeInfo.php
index 0b991df..9d137f8 100644
--- a/src/Utils/TypeInfo.php
+++ b/src/Utils/TypeInfo.php
@@ -24,7 +24,6 @@ use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Definition\UnionType;
 use GraphQL\Type\Definition\WrappingType;
 use GraphQL\Type\Introspection;
-use GraphQL\Utils\Utils;
 
 /**
  * Class TypeInfo
diff --git a/tests/Executor/UnionInterfaceTest.php b/tests/Executor/UnionInterfaceTest.php
index 7d6ac5c..4a9f0f2 100644
--- a/tests/Executor/UnionInterfaceTest.php
+++ b/tests/Executor/UnionInterfaceTest.php
@@ -3,6 +3,7 @@ namespace GraphQL\Tests\Executor;
 
 require_once __DIR__ . '/TestClasses.php';
 
+use GraphQL\Error\Warning;
 use GraphQL\Executor\Executor;
 use GraphQL\GraphQL;
 use GraphQL\Language\Parser;
@@ -256,9 +257,9 @@ class UnionInterfaceTest extends \PHPUnit_Framework_TestCase
             ]
         ];
 
-        GraphQL::setIgnoreError(GraphQL::WARNING_ON_IMPLEMENTATION_RESOLUTION);
+        Warning::suppress(Warning::RESOLVE_TYPE_WARNING);
         $this->assertEquals($expected, Executor::execute($this->schema, $ast, $this->john)->toArray());
-        GraphQL::setIgnoreError(GraphQL::WARNING_ON_IMPLEMENTATION_RESOLUTION, false);
+        Warning::enable(Warning::RESOLVE_TYPE_WARNING);
     }
 
     /**
@@ -294,9 +295,9 @@ class UnionInterfaceTest extends \PHPUnit_Framework_TestCase
             ]
         ];
 
-        GraphQL::setIgnoreError(GraphQL::WARNING_ON_IMPLEMENTATION_RESOLUTION);
+        Warning::suppress(Warning::RESOLVE_TYPE_WARNING);
         $this->assertEquals($expected, Executor::execute($this->schema, $ast, $this->john)->toArray());
-        GraphQL::setIgnoreError(GraphQL::WARNING_ON_IMPLEMENTATION_RESOLUTION, false);
+        Warning::enable(Warning::RESOLVE_TYPE_WARNING);
     }
 
     /**
@@ -351,9 +352,9 @@ class UnionInterfaceTest extends \PHPUnit_Framework_TestCase
             ]
         ];
 
-        GraphQL::setIgnoreError(GraphQL::WARNING_ON_IMPLEMENTATION_RESOLUTION);
+        Warning::suppress(Warning::RESOLVE_TYPE_WARNING);
         $this->assertEquals($expected, Executor::execute($this->schema, $ast, $this->john)->toArray());
-        GraphQL::setIgnoreError(GraphQL::WARNING_ON_IMPLEMENTATION_RESOLUTION, false);
+        Warning::enable(Warning::RESOLVE_TYPE_WARNING);
     }
 
     /**