diff --git a/ocfl_export.services.yml b/ocfl_export.services.yml
index c7ed67b..e3d3361 100644
--- a/ocfl_export.services.yml
+++ b/ocfl_export.services.yml
@@ -13,6 +13,7 @@ services:
     arguments:
       - '@entity_type.manager'
       - '@datetime.time'
+      - '@config.factory'
 
   ocfl_export.media_serializer:
     class: Drupal\ocfl_export\MediaSerializerService
diff --git a/src/MediaSerializerService.php b/src/MediaSerializerService.php
index e02ebf1..2c5ca06 100644
--- a/src/MediaSerializerService.php
+++ b/src/MediaSerializerService.php
@@ -38,6 +38,7 @@ class MediaSerializerService {
 
     $data = [
       'uuid' => $media->uuid(),
+      'mid' => (int) $media->id(),
       'type' => $media->bundle(),
       'name' => $media->getName(),
       'created' => $this->formatTimestamp((int) $media->getCreatedTime()),
@@ -363,6 +364,7 @@ class MediaSerializerService {
   protected function serializeMediaReference(MediaInterface $media): array {
     $data = [
       'uuid' => $media->uuid(),
+      'mid' => (int) $media->id(),
       'bundle' => $media->bundle(),
       'name' => $media->getName(),
       'status' => $media->isPublished(),
@@ -419,6 +421,7 @@ class MediaSerializerService {
   protected function serializeNodeReference(NodeInterface $node): array {
     return [
       'uuid' => $node->uuid(),
+      'nid' => (int) $node->id(),
       'type' => $node->bundle(),
       'title' => $node->getTitle(),
       'status' => $node->isPublished(),
diff --git a/src/NodeSerializerService.php b/src/NodeSerializerService.php
index e6c0189..77fa289 100644
--- a/src/NodeSerializerService.php
+++ b/src/NodeSerializerService.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace Drupal\ocfl_export;
 
 use Drupal\Component\Datetime\TimeInterface;
+use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\media\MediaInterface;
@@ -18,9 +19,15 @@ use Drupal\user\UserInterface;
  */
 class NodeSerializerService {
 
+  /**
+   * Maximum number of ancestors followed when building hierarchy paths.
+   */
+  protected const MAX_HIERARCHY_DEPTH = 50;
+
   public function __construct(
     protected EntityTypeManagerInterface $entityTypeManager,
     protected TimeInterface $time,
+    protected ConfigFactoryInterface $configFactory,
   ) {}
 
   /**
@@ -37,6 +44,7 @@ class NodeSerializerService {
 
     $data = [
       'uuid' => $node->uuid(),
+      'nid' => (int) $node->id(),
       'type' => $node->bundle(),
       'title' => $node->getTitle(),
       'created' => $this->formatTimestamp((int) $node->getCreatedTime()),
@@ -47,6 +55,7 @@ class NodeSerializerService {
         'name' => $author->getAccountName(),
         'display_name' => $author->getDisplayName(),
       ],
+      'relationships' => $this->serializeRelationships($node),
       'fields' => $this->serializeFields($node),
       '_metadata' => [
         'ocfl_version' => '1.1',
@@ -58,6 +67,155 @@ class NodeSerializerService {
     return $data;
   }
 
+  /**
+   * Serialize Islandora-style membership (isMemberOf) and model information.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node.
+   *
+   * @return array
+   *   An array with 'model', 'member_of' (direct parents) and 'hierarchy'
+   *   (every ancestor path, each ordered from the root down to the direct
+   *   parent). Keys are omitted when the corresponding field is not present.
+   */
+  protected function serializeRelationships(NodeInterface $node): array {
+    $config = $this->configFactory->get('ocfl_export.settings');
+    $modelField = $config->get('model_field');
+    $memberOfField = $config->get('member_of_field');
+    $relationships = [];
+
+    if ($modelField && $node->hasField($modelField)) {
+      $relationships['model'] = $this->getModel($node);
+    }
+
+    if ($memberOfField && $node->hasField($memberOfField)) {
+      $relationships['member_of'] = array_map(
+        fn (NodeInterface $parent) => $this->summarizeHierarchyNode($parent),
+        $this->getMemberOfParents($node),
+      );
+      $relationships['hierarchy'] = $this->buildAncestorPaths($node);
+    }
+
+    return $relationships;
+  }
+
+  /**
+   * Get the parent nodes a node is a member of.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node.
+   *
+   * @return \Drupal\node\NodeInterface[]
+   *   The parent nodes.
+   */
+  protected function getMemberOfParents(NodeInterface $node): array {
+    $field = $this->configFactory->get('ocfl_export.settings')->get('member_of_field');
+    if (!$field || !$node->hasField($field)) {
+      return [];
+    }
+
+    return array_values(array_filter(
+      $node->get($field)->referencedEntities(),
+      fn ($entity) => $entity instanceof NodeInterface,
+    ));
+  }
+
+  /**
+   * Build every ancestor path for a node via the member-of field.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node.
+   * @param int[] $visited
+   *   Node IDs already on the current path, to guard against cycles.
+   *
+   * @return array
+   *   A list of paths. Each path is a list of node summaries ordered from the
+   *   root collection down to the node's direct parent.
+   */
+  protected function buildAncestorPaths(NodeInterface $node, array $visited = []): array {
+    $visited[] = (int) $node->id();
+    if (count($visited) > static::MAX_HIERARCHY_DEPTH) {
+      return [];
+    }
+
+    $paths = [];
+    foreach ($this->getMemberOfParents($node) as $parent) {
+      if (in_array((int) $parent->id(), $visited, TRUE)) {
+        continue;
+      }
+
+      $summary = $this->summarizeHierarchyNode($parent);
+      $parentPaths = $this->buildAncestorPaths($parent, $visited);
+      if (!$parentPaths) {
+        $paths[] = [$summary];
+        continue;
+      }
+      foreach ($parentPaths as $path) {
+        $path[] = $summary;
+        $paths[] = $path;
+      }
+    }
+
+    return $paths;
+  }
+
+  /**
+   * Summarize a node for membership and hierarchy listings.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node.
+   *
+   * @return array
+   *   The node summary.
+   */
+  protected function summarizeHierarchyNode(NodeInterface $node): array {
+    $summary = [
+      'nid' => (int) $node->id(),
+      'uuid' => $node->uuid(),
+      'title' => $node->getTitle(),
+      'type' => $node->bundle(),
+    ];
+
+    $model = $this->getModel($node);
+    if ($model) {
+      $summary['model'] = $model['name'];
+    }
+
+    return $summary;
+  }
+
+  /**
+   * Get the Islandora model term of a node.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node.
+   *
+   * @return array|null
+   *   The model name, term UUID and external URI (if any), or NULL.
+   */
+  protected function getModel(NodeInterface $node): ?array {
+    $field = $this->configFactory->get('ocfl_export.settings')->get('model_field');
+    if (!$field || !$node->hasField($field)) {
+      return NULL;
+    }
+
+    $term = $node->get($field)->entity;
+    if (!$term instanceof TermInterface) {
+      return NULL;
+    }
+
+    $model = [
+      'tid' => (int) $term->id(),
+      'uuid' => $term->uuid(),
+      'name' => $term->getName(),
+    ];
+    if ($term->hasField('field_external_uri') && !$term->get('field_external_uri')->isEmpty()) {
+      $model['uri'] = $term->get('field_external_uri')->uri;
+    }
+
+    return $model;
+  }
+
   /**
    * Serialize all fields of a node.
    *
@@ -301,6 +459,7 @@ class NodeSerializerService {
   protected function serializeMedia(MediaInterface $media): array {
     $data = [
       'uuid' => $media->uuid(),
+      'mid' => (int) $media->id(),
       'name' => $media->getName(),
       'bundle' => $media->bundle(),
     ];
@@ -355,6 +514,7 @@ class NodeSerializerService {
   protected function serializeNodeReference(NodeInterface $node): array {
     return [
       'uuid' => $node->uuid(),
+      'nid' => (int) $node->id(),
       'type' => $node->bundle(),
       'title' => $node->getTitle(),
       'status' => $node->isPublished(),