diff --git a/src/Server/AuthorizationServer.php b/src/Server/AuthorizationServer.php
index 9e84360..a5d8637 100644
--- a/src/Server/AuthorizationServer.php
+++ b/src/Server/AuthorizationServer.php
@@ -39,7 +39,7 @@
  * @author  Michaël Gallego <mic.gallego@gmail.com>
  * @licence MIT
  */
-class AuthorizationServer implements EventManagerAwareInterface
+class AuthorizationServer implements AuthorizationServerInterface, EventManagerAwareInterface
 {
     use EventManagerAwareTrait;
 
diff --git a/src/Server/AuthorizationServerInterface.php b/src/Server/AuthorizationServerInterface.php
new file mode 100644
index 0000000..ce80018
--- /dev/null
+++ b/src/Server/AuthorizationServerInterface.php
@@ -0,0 +1,69 @@
+<?php
+/*
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * This software consists of voluntary contributions made by many individuals
+ * and is licensed under the MIT license.
+ */
+
+namespace ZfrOAuth2\Server;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use ZfrOAuth2\Server\Entity\TokenOwnerInterface;
+use ZfrOAuth2\Server\Exception\OAuth2Exception;
+
+/**
+ * The authorization server main role is to create access tokens or refresh tokens
+ */
+interface AuthorizationServerInterface
+{
+    /**
+     * Check if the authorization server supports this grant
+     *
+     * @param  string $grant
+     * @return bool
+     */
+    public function hasGrant($grant);
+
+    /**
+     * Check if the authorization server supports this response type
+     *
+     * @param  string $responseType
+     * @return bool
+     */
+    public function hasResponseType($responseType);
+
+    /**
+     * @param  ServerRequestInterface   $request
+     * @param  TokenOwnerInterface|null $owner
+     * @return ResponseInterface
+     * @throws OAuth2Exception If no "response_type" could be found in the GET parameters
+     */
+    public function handleAuthorizationRequest(ServerRequestInterface $request, TokenOwnerInterface $owner = null);
+
+    /**
+     * @param  ServerRequestInterface   $request
+     * @param  TokenOwnerInterface|null $owner
+     * @return ResponseInterface
+     * @throws OAuth2Exception If no "grant_type" could be found in the POST parameters
+     */
+    public function handleTokenRequest(ServerRequestInterface $request, TokenOwnerInterface $owner = null);
+
+    /**
+     * @param  ServerRequestInterface $request
+     * @return ResponseInterface
+     * @throws OAuth2Exception If no "token" is present
+     */
+    public function handleRevocationRequest(ServerRequestInterface $request);
+}
\ No newline at end of file
diff --git a/src/Server/Grant/AuthorizationServerAwareInterface.php b/src/Server/Grant/AuthorizationServerAwareInterface.php
index a8cfec0..1d9c702 100644
--- a/src/Server/Grant/AuthorizationServerAwareInterface.php
+++ b/src/Server/Grant/AuthorizationServerAwareInterface.php
@@ -18,7 +18,7 @@
 
 namespace ZfrOAuth2\Server\Grant;
 
-use ZfrOAuth2\Server\AuthorizationServer;
+use ZfrOAuth2\Server\AuthorizationServerInterface;
 
 /**
  * Interface for grant that need to have access to the authorization server
@@ -31,8 +31,8 @@ interface AuthorizationServerAwareInterface
     /**
      * Set the authorization server
      *
-     * @param  AuthorizationServer $authorizationServer
+     * @param  AuthorizationServerInterface $authorizationServer
      * @return void
      */
-    public function setAuthorizationServer(AuthorizationServer $authorizationServer);
+    public function setAuthorizationServer(AuthorizationServerInterface $authorizationServer);
 }
diff --git a/src/Server/Grant/AuthorizationServerAwareTrait.php b/src/Server/Grant/AuthorizationServerAwareTrait.php
index 8207b9e..145d95d 100644
--- a/src/Server/Grant/AuthorizationServerAwareTrait.php
+++ b/src/Server/Grant/AuthorizationServerAwareTrait.php
@@ -18,7 +18,7 @@
 
 namespace ZfrOAuth2\Server\Grant;
 
-use ZfrOAuth2\Server\AuthorizationServer;
+use ZfrOAuth2\Server\AuthorizationServerInterface;
 
 /**
  * @author  Michaël Gallego <mic.gallego@gmail.com>
@@ -27,14 +27,14 @@
 trait AuthorizationServerAwareTrait
 {
     /**
-     * @var AuthorizationServer
+     * @var AuthorizationServerInterface
      */
     protected $authorizationServer;
 
     /**
      * {@inheritDoc}
      */
-    public function setAuthorizationServer(AuthorizationServer $authorizationServer)
+    public function setAuthorizationServer(AuthorizationServerInterface $authorizationServer)
     {
         $this->authorizationServer = $authorizationServer;
     }
diff --git a/src/Server/ResourceServer.php b/src/Server/ResourceServer.php
index 17f1630..b19a2a8 100644
--- a/src/Server/ResourceServer.php
+++ b/src/Server/ResourceServer.php
@@ -33,7 +33,7 @@
  * @author  Michaël Gallego <mic.gallego@gmail.com>
  * @licence MIT
  */
-class ResourceServer
+class ResourceServer implements ResourceServerInterface
 {
     /**
      * @var TokenService
diff --git a/src/Server/ResourceServerInterface.php b/src/Server/ResourceServerInterface.php
new file mode 100644
index 0000000..1adbd42
--- /dev/null
+++ b/src/Server/ResourceServerInterface.php
@@ -0,0 +1,43 @@
+<?php
+/*
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * This software consists of voluntary contributions made by many individuals
+ * and is licensed under the MIT license.
+ */
+
+namespace ZfrOAuth2\Server;
+
+use Psr\Http\Message\ServerRequestInterface;
+use ZfrOAuth2\Server\Entity\AccessToken;
+use ZfrOAuth2\Server\Entity\Scope;
+
+/**
+ * The resource server main role is to validate the access token and that its scope covers the
+ * requested resource
+ *
+ * Currently, the resource server only implements the Bearer token usage, as described in the
+ * RFC 6750 (http://tools.ietf.org/html/rfc6750)
+ */
+interface ResourceServerInterface
+{
+    /**
+     * Get the access token
+     *
+     * @param  ServerRequestInterface $request
+     * @param  array|string|Scope[] $scopes
+     * @return AccessToken|null
+     * @throws Exception\InvalidAccessTokenException If given access token is invalid or expired
+     */
+    public function getAccessToken(ServerRequestInterface $request, $scopes = []);
+}
\ No newline at end of file