diff --git a/README.md b/README.md
index 429587b..ee24a25 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,98 @@
 # OWC IDP UserData
 
-This repository contains interfaces for userdata objects to be used by IDP plugins (e.g. DigiD, eHerkenning)
\ No newline at end of file
+This package provides common `UserData` and `Session` classes for identity provider (IDP) plugins such as DigiD, eHerkenning, and eIDAS.
+
+## Installation
+
+Install via Composer:
+
+```bash
+composer require owc/idp-userdata
+```
+
+### Example: Providing User Data via IDP-Specific Filters
+
+To provide user data to the session classes, use the IDP-specific WordPress filters in your plugin or theme:
+
+```php
+use OWC\IdpUserData\DigiDUserData;
+
+add_filter('owc_digid_is_logged_in', function (bool $isLoggedIn): bool {
+    // Your logic to determine if the user is logged in with DigiD
+    return true;
+});
+
+add_filter('owc_digid_userdata', function (?DigiDUserData $userData): ?DigiDUserData {
+    return new DigiDUserData([
+        'bsn' => '123456789',
+    ]);
+});
+```
+
+### Example: Providing User Data via Generic Filter (with switch)
+
+You can also use the generic filters and handle multiple IDPs with a switch statement:
+
+```php
+
+use OWC\IdpUserData\DigiDUserData;
+use OWC\IdpUserData\eHerkenningUserData;
+use OWC\IdpUserData\eIDASUserData;
+use OWC\IdpUserData\IdpSession;
+use OWC\IdpUserData\Idp;
+use OWC\IdpUserData\UserData;
+
+
+add_filter('owc_idp_is_logged_in', function (bool $isLoggedIn, string $idp): bool {
+    switch ($idp) {
+        case Idp::DIGID:
+            // Your logic for DigiD
+            return true;
+        case Idp::EHERKENNING:
+            // Your logic for eHerkenning
+            return false;
+        case Idp::EIDAS:
+            // Your logic for eIDAS
+            return false;
+        default:
+            return $isLoggedIn;
+    }
+}, 10, 2);
+
+add_filter('owc_idp_userdata', function (?UserData $userData, string $idp): ?UserData {
+    switch ($idp) {
+        case Idp::DIGID:
+            return new DigiDUserData([
+                'bsn' => '123456789',
+            ]);
+        case Idp::EHERKENNING:
+            return new eHerkenningUserData([
+                'kvk' => '987654321',
+                'rsin' => '123456789',
+                'vestigingsnummer' => '001',
+                'bsn' => null,
+            ]);
+        case Idp::EIDAS:
+            return new eIDASUserData([
+                'bsn' => '555555555',
+            ]);
+        default:
+            return $userData;
+    }
+}, 10, 2);
+```
+
+### Example: Getting User Data
+
+```php
+use OWC\IdpUserData\DigiDSession;
+use OWC\IdpUserData\DigiDUserData;
+
+if (DigiDSession::isLoggedIn()) {
+    $userData = DigiDSession::getUserData();
+    if ($userData instanceof DigiDUserData) {
+        $bsn = $userData->getBsn();
+        // ...
+    }
+}
+```
diff --git a/composer.json b/composer.json
index e75daf2..d3a4f35 100644
--- a/composer.json
+++ b/composer.json
@@ -1,7 +1,7 @@
 {
     "name": "owc/idp-userdata",
     "type": "library",
-    "description": "Common interfaces for IDP userdata (DigiD, eHerkenning)",
+    "description": "Common userdata classes and session helpers for IDP userdata (DigiD, eHerkenning)",
     "authors": [
         {
             "name": "Yard | Digital Agency",
diff --git a/src/DigiDSession.php b/src/DigiDSession.php
index 47be9cd..450e1d9 100644
--- a/src/DigiDSession.php
+++ b/src/DigiDSession.php
@@ -8,10 +8,10 @@ class DigiDSession extends IdpSession
 {
     protected static function get_idp(): string
     {
-        return 'digid';
+        return Idp::DIGID;
     }
 
-    public static function getUserData(): ?DigiDUserDataInterface
+    public static function getUserData(): ?DigiDUserData
     {
         return parent::getUserData();
     }
diff --git a/src/DigiDUserData.php b/src/DigiDUserData.php
new file mode 100644
index 0000000..bdc60d5
--- /dev/null
+++ b/src/DigiDUserData.php
@@ -0,0 +1,14 @@
+<?php
+
+namespace OWC\IdpUserData;
+
+class DigiDUserData extends UserData
+{
+    protected string $bsn;
+
+    public function getBsn(): string
+    {
+        return $this->bsn;
+    }
+
+}
\ No newline at end of file
diff --git a/src/DigiDUserDataInterface.php b/src/DigiDUserDataInterface.php
deleted file mode 100644
index 48f8fd8..0000000
--- a/src/DigiDUserDataInterface.php
+++ /dev/null
@@ -1,10 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace OWC\IdpUserData;
-
-interface DigiDUserDataInterface extends UserDataInterface
-{
-    public function getBsn(): string;
-}
diff --git a/src/Idp.php b/src/Idp.php
new file mode 100644
index 0000000..4348143
--- /dev/null
+++ b/src/Idp.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace OWC\IdpUserData;
+
+// TODO: Convert to enums if PHP 8.1+ is supported
+class Idp {
+    public const DIGID = 'digid';
+    public const EHERKENNING = 'eherkenning';
+    public const EIDAS = 'eidas';
+}
\ No newline at end of file
diff --git a/src/IdpSession.php b/src/IdpSession.php
index 2d59e29..be47485 100644
--- a/src/IdpSession.php
+++ b/src/IdpSession.php
@@ -15,7 +15,7 @@ public static function isLoggedIn(): bool
         return apply_filters('owc_' . static::get_idp() . '_is_logged_in', $isLoggedIn);
     }
 
-    protected static function getUserData(): ?UserDataInterface
+    protected static function getUserData(): ?UserData
     {
         $userData = apply_filters('owc_idp_userdata', null, static::get_idp());
 
diff --git a/src/UserData.php b/src/UserData.php
new file mode 100644
index 0000000..2fce8c0
--- /dev/null
+++ b/src/UserData.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace OWC\IdpUserData;
+
+abstract class UserData
+{
+    protected array $data;
+
+    public function __construct(array $data) {
+        $classVars = get_class_vars(static::class);
+
+        $data = wp_parse_args($data, $classVars);
+        $data = wp_array_slice_assoc($data, array_keys($classVars));
+
+        foreach ($data as $key => $value) {
+            $this->$key = $value;
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/UserDataInterface.php b/src/UserDataInterface.php
deleted file mode 100644
index a702e91..0000000
--- a/src/UserDataInterface.php
+++ /dev/null
@@ -1,9 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace OWC\IdpUserData;
-
-interface UserDataInterface
-{
-}
diff --git a/src/eHerkenningSession.php b/src/eHerkenningSession.php
index d1828ab..17cb8d3 100644
--- a/src/eHerkenningSession.php
+++ b/src/eHerkenningSession.php
@@ -8,10 +8,10 @@ class eHerkenningSession extends IdpSession
 {
     protected static function get_idp(): string
     {
-        return 'eherkenning';
+        return Idp::EHERKENNING;
     }
 
-    public static function getUserData(): ?eHerkenningUserDataInterface
+    public static function getUserData(): ?eHerkenningUserData
     {
         return parent::getUserData();
     }
diff --git a/src/eHerkenningUserData.php b/src/eHerkenningUserData.php
new file mode 100644
index 0000000..fdbc862
--- /dev/null
+++ b/src/eHerkenningUserData.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace OWC\IdpUserData;
+
+class eHerkenningUserdata extends UserData
+{
+    protected string $kvk;
+
+    protected ?string $rsin = null;
+
+    protected ?string $vestigingsnummer = null;
+
+    protected ?string $bsn = null;
+
+    public function getKvk(): string
+    {
+        return $this->kvk;
+    }
+
+    public function getBsn(): ?string
+    {
+        return $this->bsn;
+    }
+
+    public function getRsin(): ?string {
+        return $this->rsin;
+    }
+
+    public function getVestigingsnummer(): ?string {
+        return $this->vestigingsnummer;
+    }
+}
\ No newline at end of file
diff --git a/src/eHerkenningUserDataInterface.php b/src/eHerkenningUserDataInterface.php
deleted file mode 100644
index 9f4508f..0000000
--- a/src/eHerkenningUserDataInterface.php
+++ /dev/null
@@ -1,10 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace OWC\IdpUserData;
-
-interface eHerkenningUserDataInterface extends UserDataInterface
-{
-    public function getKvk(): string;
-}
diff --git a/src/eIDASSession.php b/src/eIDASSession.php
index 3168e20..a0aa57e 100644
--- a/src/eIDASSession.php
+++ b/src/eIDASSession.php
@@ -8,10 +8,10 @@ class eIDASSession extends IdpSession
 {
     protected static function get_idp(): string
     {
-        return 'eidas';
+        return Idp::EIDAS;
     }
 
-    public static function getUserData(): ?eIDASUserDataInterface
+    public static function getUserData(): ?eIDASUserData
     {
         return parent::getUserData();
     }
diff --git a/src/eIDASUserData.php b/src/eIDASUserData.php
new file mode 100644
index 0000000..c01adaf
--- /dev/null
+++ b/src/eIDASUserData.php
@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OWC\IdpUserData;
+
+class eIDASUserData extends UserData
+{
+    protected string $bsn;
+
+    public function getBsn(): string {
+        return $this->bsn;
+    }
+}
diff --git a/src/eIDASUserDataInterface.php b/src/eIDASUserDataInterface.php
deleted file mode 100644
index af608d4..0000000
--- a/src/eIDASUserDataInterface.php
+++ /dev/null
@@ -1,10 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace OWC\IdpUserData;
-
-interface eIDASUserDataInterface extends UserDataInterface
-{
-    public function getBsn(): string;
-}