diff --git a/core/core.services.yml b/core/core.services.yml
index 5b0de75..c9db07b 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1657,3 +1657,8 @@ services:
     class: Drupal\Core\EventSubscriber\RssResponseRelativeUrlFilter
     tags:
       - { name: event_subscriber }
+  core.workflow_type_manager:
+    class: Drupal\Core\Workflow\WorkflowTypeManager
+    parent: default_plugin_manager
+    tags:
+      - { name: plugin_manager_cache_clear }
diff --git a/core/lib/Drupal/Core/Workflow/Annotation/WorkflowType.php b/core/lib/Drupal/Core/Workflow/Annotation/WorkflowType.php
new file mode 100644
index 0000000..8d5c046
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/Annotation/WorkflowType.php
@@ -0,0 +1,44 @@
+<?php
+
+namespace Drupal\Core\Workflow\Annotation;
+
+use Drupal\Component\Annotation\Plugin;
+
+/**
+ * Defines an Workflow type annotation object.
+ *
+ * Plugin Namespace: Plugin\WorkflowType
+ *
+ * For a working example, see \Drupal\content_moderation\Plugin\Workflow\ContentModerate
+ *
+ * @see \Drupal\Core\Workflow\WorkflowTypeInterface
+ * @see \Drupal\Core\Workflow\WorkflowManager
+ * @see plugin_api
+ *
+ * @Annotation
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+class WorkflowType extends Plugin {
+
+  /**
+   * The plugin ID.
+   *
+   * @var string
+   */
+  public $id;
+
+  /**
+   * The label of the workflow.
+   *
+   * Describes how the plugin is used to apply a workflow to something.
+   *
+   * @var \Drupal\Core\Annotation\Translation
+   *
+   * @ingroup plugin_translatable
+   */
+  public $label = '';
+
+}
diff --git a/core/lib/Drupal/Core/Workflow/Entity/Workflow.php b/core/lib/Drupal/Core/Workflow/Entity/Workflow.php
new file mode 100644
index 0000000..21389af
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/Entity/Workflow.php
@@ -0,0 +1,497 @@
+<?php
+
+namespace Drupal\Core\Workflow\Entity;
+
+use Drupal\Core\Config\Entity\ConfigEntityBase;
+use Drupal\Core\Entity\EntityWithPluginCollectionInterface;
+use Drupal\Core\Plugin\DefaultSingleLazyPluginCollection;
+use Drupal\Core\Workflow\State;
+use Drupal\Core\Workflow\Transition;
+use Drupal\Core\Workflow\WorkflowInterface;
+
+/**
+ * Defines the workflow entity.
+ *
+ * @ConfigEntityType(
+ *   id = "workflow",
+ *   label = @Translation("Workflow"),
+ *   handlers = {
+ *     "access" = "Drupal\Core\Workflow\WorkflowAccessControlHandler",
+ *     "route_provider" = {
+ *       "html" = "Drupal\Core\Entity\Routing\AdminHtmlRouteProvider",
+ *     },
+ *   },
+ *   config_prefix = "workflow",
+ *   entity_keys = {
+ *     "id" = "id",
+ *     "label" = "label",
+ *     "uuid" = "uuid",
+ *   },
+ *   config_export = {
+ *     "id",
+ *     "label",
+ *     "states",
+ *     "transitions",
+ *     "type",
+ *     "type_settings"
+ *   },
+ * )
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+class Workflow extends ConfigEntityBase implements WorkflowInterface, EntityWithPluginCollectionInterface {
+
+  /**
+   * The Workflow ID.
+   *
+   * @var string
+   */
+  protected $id;
+
+  /**
+   * The Moderation state label.
+   *
+   * @var string
+   */
+  protected $label;
+
+  /**
+   * The states of the workflow.
+   *
+   * The array key is the machine name for the state. The structure of each
+   * array item is:
+   * @code
+   *   label: {translatable label}
+   *   weight: {integer value}
+   * @endcode
+   *
+   * @var array
+   */
+  protected $states = [];
+
+  /**
+   * The permitted transitions of the workflow.
+   *
+   * The array key is the machine name for the transition. The machine name is
+   * generated from the machine names of the states. The structure of each array
+   * item is:
+   * @code
+   *   from:
+   *     - {state machine name}
+   *     - {state machine name}
+   *   to: {state machine name}
+   *   label: {translatable label}
+   * @endcode
+   *
+   * @var array
+   */
+  protected $transitions = [];
+
+  /**
+   * The workflow type plugin ID.
+   *
+   * @see \Drupal\Core\Workflow\WorkflowTypeManager
+   *
+   * @var string
+   */
+  protected $type;
+
+  /**
+   * The configuration for the workflow type plugin.
+   * @var array
+   */
+  protected $type_settings = [];
+
+  /**
+   * The workflow type plugin collection.
+   *
+   * @var \Drupal\Component\Plugin\LazyPluginCollection
+   */
+  protected $pluginCollection;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addState($state_id, $label) {
+    if (isset($this->states[$state_id])) {
+      throw new \InvalidArgumentException("The state '$state_id' already exists in workflow '{$this->id()}'");
+    }
+    if (preg_match('/[^a-z0-9_]+/', $state_id)) {
+      throw new \InvalidArgumentException("The state ID '$state_id' must contain only lowercase letters, numbers, and underscores");
+    }
+    $this->states[$state_id] = [
+      'label' => $label,
+      'weight' => $this->getNextWeight($this->states),
+    ];
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasState($state_id) {
+    return isset($this->states[$state_id]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getStates($state_ids = NULL) {
+    if ($state_ids === NULL) {
+      $state_ids = array_keys($this->states);
+    }
+    /** @var \Drupal\Core\Workflow\StateInterface[] $states */
+    $states = array_combine($state_ids, array_map([$this, 'getState'], $state_ids));
+    if (count($states) > 1) {
+      // Sort states by weight and then label.
+      $weights = $labels = [];
+      foreach ($states as $id => $state) {
+        $weights[$id] = $state->weight();
+        $labels[$id] = $state->label();
+      }
+      array_multisort(
+        $weights, SORT_NUMERIC, SORT_ASC,
+        $labels, SORT_NATURAL, SORT_ASC
+      );
+      $states = array_replace($weights, $states);
+    }
+    return $states;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getState($state_id) {
+    if (!isset($this->states[$state_id])) {
+      throw new \InvalidArgumentException("The state '$state_id' does not exist in workflow '{$this->id()}'");
+    }
+    $state = new State(
+      $this,
+      $state_id,
+      $this->states[$state_id]['label'],
+      $this->states[$state_id]['weight']
+    );
+    return $this->getTypePlugin()->decorateState($state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setStateLabel($state_id, $label) {
+    if (!isset($this->states[$state_id])) {
+      throw new \InvalidArgumentException("The state '$state_id' does not exist in workflow '{$this->id()}'");
+    }
+    $this->states[$state_id]['label'] = $label;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setStateWeight($state_id, $weight) {
+    if (!isset($this->states[$state_id])) {
+      throw new \InvalidArgumentException("The state '$state_id' does not exist in workflow '{$this->id()}'");
+    }
+    $this->states[$state_id]['weight'] = $weight;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function deleteState($state_id) {
+    if (!isset($this->states[$state_id])) {
+      throw new \InvalidArgumentException("The state '$state_id' does not exist in workflow '{$this->id()}'");
+    }
+    foreach ($this->transitions as $transition_id => $transition) {
+      $from_key = array_search($state_id, $transition['from'], TRUE);
+      if ($from_key !== FALSE) {
+        // Remove state from the from array.
+        unset($transition['from'][$from_key]);
+      }
+      if (empty($transition['from']) || $transition['to'] === $state_id) {
+        $this->deleteTransition($transition_id);
+      }
+      elseif ($from_key !== FALSE) {
+        $this->setTransitionFromStates($transition_id, $transition['from']);
+      }
+    }
+    unset($this->states[$state_id]);
+    $this->getTypePlugin()->deleteState($state_id);
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getInitialState() {
+    $ordered_states = $this->getStates();
+    return reset($ordered_states);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addTransition($transition_id, $label, array $from_state_ids, $to_state_id) {
+    if (isset($this->transitions[$transition_id])) {
+      throw new \InvalidArgumentException("The transition '$transition_id' already exists in workflow '{$this->id()}'");
+    }
+    if (preg_match('/[^a-z0-9_]+/', $transition_id)) {
+      throw new \InvalidArgumentException("The transition ID '$transition_id' must contain only lowercase letters, numbers, and underscores");
+    }
+
+    if (!$this->hasState($to_state_id)) {
+      throw new \InvalidArgumentException("The state '$to_state_id' does not exist in workflow '{$this->id()}'");
+    }
+    $this->transitions[$transition_id] = [
+      'label' => $label,
+      'from' => [],
+      'to' => $to_state_id,
+      // Always add to the end.
+      'weight' => $this->getNextWeight($this->transitions),
+    ];
+
+    try {
+      $this->setTransitionFromStates($transition_id, $from_state_ids);
+    }
+    catch (\InvalidArgumentException $e) {
+      unset($this->transitions[$transition_id]);
+      throw $e;
+    }
+
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTransitions(array $transition_ids = NULL) {
+    if ($transition_ids === NULL) {
+      $transition_ids = array_keys($this->transitions);
+    }
+    /** @var \Drupal\Core\Workflow\TransitionInterface[] $transitions */
+    $transitions = array_combine($transition_ids, array_map([$this, 'getTransition'], $transition_ids));
+    if (count($transitions) > 1) {
+      // Sort transitions by weights and then labels.
+      $weights = $labels = [];
+      foreach ($transitions as $id => $transition) {
+        $weights[$id] = $transition->weight();
+        $labels[$id] = $transition->label();
+      }
+      array_multisort(
+        $weights, SORT_NUMERIC, SORT_ASC,
+        $labels, SORT_NATURAL, SORT_ASC
+      );
+      $transitions = array_replace($weights, $transitions);
+    }
+    return $transitions;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTransition($transition_id) {
+    if (!isset($this->transitions[$transition_id])) {
+      throw new \InvalidArgumentException("The transition '$transition_id' does not exist in workflow '{$this->id()}'");
+    }
+    $transition = new Transition(
+      $this,
+      $transition_id,
+      $this->transitions[$transition_id]['label'],
+      $this->transitions[$transition_id]['from'],
+      $this->transitions[$transition_id]['to'],
+      $this->transitions[$transition_id]['weight']
+    );
+    return $this->getTypePlugin()->decorateTransition($transition);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasTransition($transition_id) {
+    return isset($this->transitions[$transition_id]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTransitionsForState($state_id, $direction = 'from') {
+    if ($direction !== 'to' && $direction !== 'from') {
+      throw new \InvalidArgumentException("The direction '$direction' is invalid, the only valid values are 'to' and 'from'");
+    }
+    $transition_ids = array_keys(array_filter($this->transitions, function ($transition) use ($state_id, $direction) {
+      return in_array($state_id, (array) $transition[$direction], TRUE);
+    }));
+    return $this->getTransitions($transition_ids);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTransitionFromStateToState($from_state_id, $to_state_id) {
+    $transition_id = $this->getTransitionIdFromStateToState($from_state_id, $to_state_id);
+    if (empty($transition_id)) {
+      throw new \InvalidArgumentException("The transition from '$from_state_id' to '$to_state_id' does not exist in workflow '{$this->id()}'");
+    }
+    return $this->getTransition($transition_id);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasTransitionFromStateToState($from_state_id, $to_state_id) {
+    return !empty($this->getTransitionIdFromStateToState($from_state_id, $to_state_id));
+  }
+
+  /**
+   * Gets the transition ID from state to state.
+   *
+   * @param string $from_state_id
+   *   The state ID to transition from.
+   * @param string $to_state_id
+   *   The state ID to transition to.
+   *
+   * @return string|null
+   *   The transition ID, or NULL if no transition exists.
+   */
+  protected function getTransitionIdFromStateToState($from_state_id, $to_state_id) {
+    foreach ($this->transitions as $transition_id => $transition) {
+      if (in_array($from_state_id, $transition['from'], TRUE) && $transition['to'] === $to_state_id) {
+        return $transition_id;
+      }
+    }
+    return NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setTransitionLabel($transition_id, $label) {
+    if (isset($this->transitions[$transition_id])) {
+      $this->transitions[$transition_id]['label'] = $label;
+    }
+    else {
+      throw new \InvalidArgumentException("The transition '$transition_id' does not exist in workflow '{$this->id()}'");
+    }
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setTransitionWeight($transition_id, $weight) {
+    if (isset($this->transitions[$transition_id])) {
+      $this->transitions[$transition_id]['weight'] = $weight;
+    }
+    else {
+      throw new \InvalidArgumentException("The transition '$transition_id' does not exist in workflow '{$this->id()}'");
+    }
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setTransitionFromStates($transition_id, array $from_state_ids) {
+    if (!isset($this->transitions[$transition_id])) {
+      throw new \InvalidArgumentException("The transition '$transition_id' does not exist in workflow '{$this->id()}'");
+    }
+
+    // Ensure that the states exist.
+    foreach ($from_state_ids as $from_state_id) {
+      if (!$this->hasState($from_state_id)) {
+        throw new \InvalidArgumentException("The state '$from_state_id' does not exist in workflow '{$this->id()}'");
+      }
+      if ($this->hasTransitionFromStateToState($from_state_id, $this->transitions[$transition_id]['to'])) {
+        $transition = $this->getTransitionFromStateToState($from_state_id, $this->transitions[$transition_id]['to']);
+        if ($transition_id !== $transition->id()) {
+          throw new \InvalidArgumentException("The '{$transition->id()}' transition already allows '$from_state_id' to '{$this->transitions[$transition_id]['to']}' transitions in workflow '{$this->id()}'");
+        }
+      }
+    }
+
+    // Preserve the order of the state IDs in the from value and don't save any
+    // keys.
+    $from_state_ids = array_values($from_state_ids);
+    sort($from_state_ids);
+    $this->transitions[$transition_id]['from'] = $from_state_ids;
+
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function deleteTransition($transition_id) {
+    if (isset($this->transitions[$transition_id])) {
+      unset($this->transitions[$transition_id]);
+      $this->getTypePlugin()->deleteTransition($transition_id);
+    }
+    else {
+      throw new \InvalidArgumentException("The transition '$transition_id' does not exist in workflow '{$this->id()}'");
+    }
+    return $this;
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function getTypePlugin() {
+    return $this->getPluginCollection()->get($this->type);
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function getPluginCollections() {
+    return ['type_settings' => $this->getPluginCollection()];
+  }
+
+  /**
+   * Encapsulates the creation of the workflow's plugin collection.
+   *
+   * @return \Drupal\Core\Plugin\DefaultSingleLazyPluginCollection
+   *   The workflow's plugin collection.
+   */
+  protected function getPluginCollection() {
+    if (!$this->pluginCollection && $this->type) {
+      $this->pluginCollection = new DefaultSingleLazyPluginCollection(\Drupal::service('core.workflow_type_manager'), $this->type, $this->type_settings);
+    }
+    return $this->pluginCollection;
+  }
+
+  /**
+   * Loads all workflows of the provided type.
+   *
+   * @param string $type
+   *   The workflow type to load all workflows for.
+   *
+   * @return static[]
+   *   An array of workflow objects of the provided workflow type, indexed by
+   *   their IDs.
+   *
+   *  @see \Drupal\Core\Workflow\Annotation\WorkflowType
+   */
+  public static function loadMultipleByType($type) {
+    return self::loadMultiple(\Drupal::entityQuery('workflow')->condition('type', $type)->execute());
+  }
+
+  /**
+   * Gets the weight for a new state or transition.
+   *
+   * @param array $items
+   *   An array of states or transitions information where each item has a
+   *   'weight' key with a numeric value.
+   *
+   * @return int
+   *   The weight for a new item in the array so that it has the highest weight.
+   */
+  protected function getNextWeight(array $items) {
+    return array_reduce($items, function ($carry, $item) {
+      return max($carry, $item['weight'] + 1);
+    }, 0);
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Workflow/Plugin/WorkflowTypeBase.php b/core/lib/Drupal/Core/Workflow/Plugin/WorkflowTypeBase.php
new file mode 100644
index 0000000..3a094b3
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/Plugin/WorkflowTypeBase.php
@@ -0,0 +1,119 @@
+<?php
+
+namespace Drupal\Core\Workflow\Plugin;
+
+use Drupal\Component\Plugin\PluginBase;
+use Drupal\Component\Utility\NestedArray;
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\Workflow\StateInterface;
+use Drupal\Core\Workflow\TransitionInterface;
+use Drupal\Core\Workflow\WorkflowInterface;
+use Drupal\Core\Workflow\WorkflowTypeInterface;
+
+/**
+ * A base class for Workflow type plugins.
+ *
+ * @see \Drupal\Core\Workflow\Annotation\WorkflowType
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+abstract class WorkflowTypeBase extends PluginBase implements WorkflowTypeInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function label() {
+    $definition = $this->getPluginDefinition();
+    // The label can be an object.
+    // @see \Drupal\Core\StringTranslation\TranslatableMarkup
+    return $definition['label'];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function checkWorkflowAccess(WorkflowInterface $entity, $operation, AccountInterface $account) {
+    return AccessResult::neutral();
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function decorateState(StateInterface $state) {
+    return $state;
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function deleteState($state_id) {
+    unset($this->configuration['states'][$state_id]);
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function decorateTransition(TransitionInterface $transition) {
+    return $transition;
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function deleteTransition($transition_id) {
+    unset($this->configuration['transitions'][$transition_id]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildStateConfigurationForm(FormStateInterface $form_state, WorkflowInterface $workflow, StateInterface $state = NULL) {
+    return [];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildTransitionConfigurationForm(FormStateInterface $form_state, WorkflowInterface $workflow, TransitionInterface $transition = NULL) {
+    return [];
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function getConfiguration() {
+    return $this->configuration;
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function setConfiguration(array $configuration) {
+    $this->configuration = NestedArray::mergeDeep(
+      $this->defaultConfiguration(),
+      $configuration
+    );
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function defaultConfiguration() {
+    return [
+      'states' => [],
+      'transitions' => [],
+    ];
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function calculateDependencies() {
+    return [];
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Workflow/State.php b/core/lib/Drupal/Core/Workflow/State.php
new file mode 100644
index 0000000..d8dea01
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/State.php
@@ -0,0 +1,118 @@
+<?php
+
+namespace Drupal\Core\Workflow;
+
+/**
+ * A value object representing a workflow state.
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+class State implements StateInterface {
+
+  /**
+   * The workflow the state is attached to.
+   *
+   * @var \Drupal\Core\Workflow\WorkflowInterface
+   */
+  protected $workflow;
+
+  /**
+   * The state's ID.
+   *
+   * @var string
+   */
+  protected $id;
+
+  /**
+   * The state's label.
+   *
+   * @var string
+   */
+  protected $label;
+
+  /**
+   * The state's weight.
+   *
+   * @var int
+   */
+  protected $weight;
+
+  /**
+   * State constructor.
+   *
+   * @param \Drupal\Core\Workflow\WorkflowInterface $workflow
+   *   The workflow the state is attached to.
+   * @param string $id
+   *   The state's ID.
+   * @param string $label
+   *   The state's label.
+   * @param int $weight
+   *   The state's weight.
+   */
+  public function __construct(WorkflowInterface $workflow, $id, $label, $weight = 0) {
+    $this->workflow = $workflow;
+    $this->id = $id;
+    $this->label = $label;
+    $this->weight = $weight;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function id() {
+    return $this->id;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function label() {
+    return $this->label;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function weight() {
+    return $this->weight;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function canTransitionTo($to_state_id) {
+    return $this->workflow->hasTransitionFromStateToState($this->id(), $to_state_id);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTransitionTo($to_state_id) {
+    if (!$this->canTransitionTo($to_state_id)) {
+      throw new \InvalidArgumentException("Can not transition to '$to_state_id' state");
+    }
+    return $this->workflow->getTransitionFromStateToState($this->id(), $to_state_id);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTransitions() {
+    return $this->workflow->getTransitionsForState($this->id());
+  }
+
+  /**
+   * Helper method to convert a list of states to labels
+   *
+   * @param \Drupal\Core\Workflow\StateInterface $state
+   *
+   * @return string
+   *   The label of the state.
+   */
+  public static function labelCallback(StateInterface $state) {
+    return $state->label();
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Workflow/StateInterface.php b/core/lib/Drupal/Core/Workflow/StateInterface.php
new file mode 100644
index 0000000..524f94b
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/StateInterface.php
@@ -0,0 +1,73 @@
+<?php
+
+namespace Drupal\Core\Workflow;
+
+/**
+ * An interface for state value objects.
+ *
+ * @see \Drupal\Core\Workflow\WorkflowTypeInterface::decorateState()
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+interface StateInterface {
+
+  /**
+   * Gets the state's ID.
+   *
+   * @return string
+   *   The state's ID.
+   */
+  public function id();
+
+  /**
+   * Gets the state's label.
+   *
+   * @return string
+   *   The state's label.
+   */
+  public function label();
+
+  /**
+   * Gets the state's weight.
+   *
+   * @return int
+   *   The state's weight.
+   */
+  public function weight();
+
+  /**
+   * Determines if the state can transition to the provided state ID.
+   *
+   * @param $to_state_id
+   *   The state to transition to.
+   *
+   * @return bool
+   *   TRUE if the state can transition to the provided state ID. FALSE, if not.
+   */
+  public function canTransitionTo($to_state_id);
+
+  /**
+   * Gets the Transition object for the provided state ID.
+   *
+   * @param $to_state_id
+   *   The state to transition to.
+   *
+   * @return \Drupal\Core\Workflow\TransitionInterface
+   *   The Transition object for the provided state ID.
+   *
+   * @throws \InvalidArgumentException()
+   *   Exception thrown when the provided state ID can not be transitioned to.
+   */
+  public function getTransitionTo($to_state_id);
+
+  /**
+   * Gets all the possible transition objects for the state.
+   *
+   * @return \Drupal\Core\Workflow\TransitionInterface[]
+   *   All the possible transition objects for the state.
+   */
+  public function getTransitions();
+
+}
diff --git a/core/lib/Drupal/Core/Workflow/Transition.php b/core/lib/Drupal/Core/Workflow/Transition.php
new file mode 100644
index 0000000..8ed3890
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/Transition.php
@@ -0,0 +1,116 @@
+<?php
+
+namespace Drupal\Core\Workflow;
+
+/**
+ * A transition value object that describes the transition between states.
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+class Transition implements TransitionInterface {
+
+  /**
+   * The workflow that this transition is attached to.
+   *
+   * @var \Drupal\Core\Workflow\WorkflowInterface
+   */
+  protected $workflow;
+
+  /**
+   * The transition's ID.
+   *
+   * @var string
+   */
+  protected $id;
+
+  /**
+   * The transition's label.
+   *
+   * @var string
+   */
+  protected $label;
+
+  /**
+   * The transition's from state IDs.
+   *
+   * @var string[]
+   */
+  protected $fromStateIds;
+
+  /**
+   * The transition's to state ID.
+   *
+   * @var string
+   */
+  protected $toStateId;
+
+  /**
+   * The transition's weight.
+   *
+   * @var int
+   */
+  protected $weight;
+
+  /**
+   * Transition constructor.
+   *
+   * @param \Drupal\Core\Workflow\WorkflowInterface $workflow
+   *   The workflow the state is attached to.
+   * @param string $id
+   *   The transition's ID.
+   * @param string $label
+   *   The transition's label.
+   * @param array $from_state_ids
+   *   A list of from state IDs.
+   * @param string $to_state_id
+   *   The to state ID.
+   * @param int $weight
+   *   (optional) The transition's weight. Defaults to 0.
+   */
+  public function __construct(WorkflowInterface $workflow, $id, $label, array $from_state_ids, $to_state_id, $weight = 0) {
+    $this->workflow = $workflow;
+    $this->id = $id;
+    $this->label = $label;
+    $this->fromStateIds = $from_state_ids;
+    $this->toStateId = $to_state_id;
+    $this->weight = $weight;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function id() {
+    return $this->id;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function label() {
+    return $this->label;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function from() {
+    return $this->workflow->getStates($this->fromStateIds);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function to() {
+    return $this->workflow->getState($this->toStateId);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function weight() {
+    return $this->weight;
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Workflow/TransitionInterface.php b/core/lib/Drupal/Core/Workflow/TransitionInterface.php
new file mode 100644
index 0000000..a819310
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/TransitionInterface.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace Drupal\Core\Workflow;
+
+/**
+ * A transition value object that describes the transition between two states.
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+interface TransitionInterface {
+
+  /**
+   * Gets the transition's ID.
+   *
+   * @return string
+   *   The transition's ID.
+   */
+  public function id();
+
+  /**
+   * Gets the transition's label.
+   *
+   * @return string
+   *   The transition's label.
+   */
+  public function label();
+
+  /**
+   * Gets the transition's from states.
+   *
+   * @return \Drupal\Core\Workflow\StateInterface[]
+   *   The transition's from states.
+   */
+  public function from();
+
+  /**
+   * Gets the transition's to state.
+   *
+   * @return \Drupal\Core\Workflow\StateInterface
+   *   The transition's to state.
+   */
+  public function to();
+
+  /**
+   * Gets the transition's weight.
+   *
+   * @return string
+   *   The transition's weight.
+   */
+  public function weight();
+
+}
diff --git a/core/lib/Drupal/Core/Workflow/WorkflowAccessControlHandler.php b/core/lib/Drupal/Core/Workflow/WorkflowAccessControlHandler.php
new file mode 100644
index 0000000..004bf47
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/WorkflowAccessControlHandler.php
@@ -0,0 +1,75 @@
+<?php
+
+namespace Drupal\Core\Workflow;
+
+use Drupal\Component\Plugin\PluginManagerInterface;
+use Drupal\Core\Entity\EntityAccessControlHandler;
+use Drupal\Core\Entity\EntityHandlerInterface;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\Access\AccessResult;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Access controller for the Moderation State entity.
+ *
+ * @see \Drupal\Core\Workflow\Entity\Workflow.
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+class WorkflowAccessControlHandler extends EntityAccessControlHandler implements EntityHandlerInterface {
+
+  /**
+   * The workflow type plugin manager.
+   *
+   * @var \Drupal\Component\Plugin\PluginManagerInterface
+   */
+  protected $workflowTypeManager;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
+    return new static(
+      $entity_type,
+      $container->get('core.workflow_type_manager')
+    );
+  }
+
+  /**
+   * Constructs the workflow access control handler instance.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
+   *   The entity type definition.
+   * @param \Drupal\Component\Plugin\PluginManagerInterface $workflow_type_manager
+   *   The workflow type plugin manager.
+   */
+  public function __construct(EntityTypeInterface $entity_type, PluginManagerInterface $workflow_type_manager) {
+    parent::__construct($entity_type);
+    $this->workflowTypeManager = $workflow_type_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function checkAccess(EntityInterface $entity, $operation, AccountInterface $account) {
+    $admin_access = parent::checkAccess($entity, $operation, $account);
+    /** @var \Drupal\Core\Workflow\WorkflowInterface $entity */
+    return $entity->getTypePlugin()->checkWorkflowAccess($entity, $operation, $account)->orIf($admin_access);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function checkCreateAccess(AccountInterface $account, array $context, $entity_bundle = NULL) {
+    $workflow_types_count = count($this->workflowTypeManager->getDefinitions());
+    $admin_access = parent::checkCreateAccess($account, $context, $entity_bundle);
+    // Allow access if there is at least one workflow type. Since workflow types
+    // are provided by modules this is cacheable until extensions change.
+    return $admin_access->andIf(AccessResult::allowedIf($workflow_types_count > 0))->addCacheTags(['config:core.extension']);
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Workflow/WorkflowInterface.php b/core/lib/Drupal/Core/Workflow/WorkflowInterface.php
new file mode 100644
index 0000000..853379e
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/WorkflowInterface.php
@@ -0,0 +1,289 @@
+<?php
+
+namespace Drupal\Core\Workflow;
+
+use Drupal\Core\Config\Entity\ConfigEntityInterface;
+
+/**
+ * Provides an interface for defining workflow entities.
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+interface WorkflowInterface extends ConfigEntityInterface {
+
+  /**
+   * Adds a state to the workflow.
+   *
+   * @param string $state_id
+   *   The state's ID.
+   * @param string $label
+   *   The state's label.
+   *
+   * @return \Drupal\Core\Workflow\WorkflowInterface
+   *   The workflow entity.
+   */
+  public function addState($state_id, $label);
+
+  /**
+   * Determines if the workflow has a state with the provided ID.
+   *
+   * @param string $state_id
+   *   The state's ID.
+   *
+   * @return bool
+   *   TRUE if the workflow has a state with the provided ID, FALSE if not.
+   */
+  public function hasState($state_id);
+
+  /**
+   * Gets state objects for the provided state IDs.
+   *
+   * @param string[] $state_ids
+   *   A list of state IDs to get. If NULL then all states will be returned.
+   *
+   * @return \Drupal\Core\Workflow\StateInterface[]
+   *   An array of workflow states.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if $state_ids contains a state ID that does not exist.
+   */
+  public function getStates($state_ids = NULL);
+
+  /**
+   * Gets a workflow state.
+   *
+   * @param string $state_id
+   *   The state's ID.
+   *
+   * @return \Drupal\Core\Workflow\StateInterface
+   *   The workflow state.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if $state_id does not exist.
+   */
+  public function getState($state_id);
+
+  /**
+   * Sets a state's label.
+   *
+   * @param string $state_id
+   *   The state ID to set the label for.
+   * @param string $label
+   *   The state's label.
+   *
+   * @return \Drupal\Core\Workflow\WorkflowInterface
+   *   The workflow entity.
+   */
+  public function setStateLabel($state_id, $label);
+
+  /**
+   * Sets a state's weight value.
+   *
+   * @param string $state_id
+   *   The state ID to set the weight for.
+   * @param int $weight
+   *   The state's weight.
+   *
+   * @return \Drupal\Core\Workflow\WorkflowInterface
+   *   The workflow entity.
+   */
+  public function setStateWeight($state_id, $weight);
+
+  /**
+   * Deletes a state from the workflow.
+   *
+   * @param string $state_id
+   *   The state ID to delete.
+   *
+   * @return \Drupal\Core\Workflow\WorkflowInterface
+   *   The workflow entity.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if $state_id does not exist.
+   */
+  public function deleteState($state_id);
+
+  /**
+   * Gets the initial state for the workflow.
+   *
+   * @return \Drupal\Core\Workflow\StateInterface
+   *   The initial state.
+   */
+  public function getInitialState();
+
+  /**
+   * Adds a transition to the workflow.
+   *
+   * @param string $id
+   *   The transition ID.
+   * @param string $label.
+   *   The transition's label.
+   * @param array $from_state_ids
+   *   The state IDs to transition from.
+   * @param string $to_state_id
+   *   The state ID to transition to.
+   *
+   * @return \Drupal\Core\Workflow\WorkflowInterface
+   *   The workflow entity.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if either state does not exist.
+   */
+  public function addTransition($id, $label, array $from_state_ids, $to_state_id);
+
+  /**
+   * Gets a transition object for the provided transition ID.
+   *
+   * @param string $transition_id
+   *   A transition ID.
+   *
+   * @return \Drupal\Core\Workflow\TransitionInterface
+   *   The transition.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if $transition_id does not exist.
+   */
+  public function getTransition($transition_id);
+
+  /**
+   * Determines if a transition exists.
+   *
+   * @param string $transition_id
+   *   The transition ID.
+   *
+   * @return bool
+   *   TRUE if the transition exists, FALSE if not.
+   */
+  public function hasTransition($transition_id);
+
+  /**
+   * Gets transition objects for the provided transition IDs.
+   *
+   * @param string[] $transition_ids
+   *   A list of transition IDs to get. If NULL then all transitions will be
+   *   returned.
+   *
+   * @return \Drupal\Core\Workflow\TransitionInterface[]
+   *   An array of transition objects.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if $transition_ids contains a transition ID that does not exist.
+   */
+  public function getTransitions(array $transition_ids = NULL);
+
+  /**
+   * Gets the transactions IDs for a state for the provided direction.
+   *
+   * @param $state_id
+   *   The state to get transitions for.
+   * @param string $direction
+   *   (optional) The direction of the transition. Defaults to 'from'. Possible
+   *   values are: 'from' and 'to'.
+   *
+   * @return array
+   *   The transactions IDs for a state for the provided direction.
+   */
+  public function getTransitionsForState($state_id, $direction = 'from');
+
+  /**
+   * Gets a transition from state to state.
+   *
+   * @param string $from_state_id
+   *   The state ID to transition from.
+   * @param string $to_state_id
+   *   The state ID to transition to.
+   *
+   * @return \Drupal\Core\Workflow\TransitionInterface
+   *   The transitions.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if the transition does not exist.
+   */
+  public function getTransitionFromStateToState($from_state_id, $to_state_id);
+
+  /**
+   * Determines if a transition from state to state exists.
+   *
+   * @param string $from_state_id
+   *   The state ID to transition from.
+   * @param string $to_state_id
+   *   The state ID to transition to.
+   *
+   * @return bool
+   *   TRUE if the transition exists, FALSE if not.
+   */
+  public function hasTransitionFromStateToState($from_state_id, $to_state_id);
+
+  /**
+   * Sets a transition's label.
+   *
+   * @param string $transition_id
+   *   The transition ID.
+   * @param string $label
+   *   The transition's label.
+   *
+   * @return \Drupal\Core\Workflow\WorkflowInterface
+   *   The workflow entity.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if the transition does not exist.
+   */
+  public function setTransitionLabel($transition_id, $label);
+
+  /**
+   * Sets a transition's weight.
+   *
+   * @param string $transition_id
+   *   The transition ID.
+   * @param int $weight
+   *   The transition's weight.
+   *
+   * @return \Drupal\Core\Workflow\WorkflowInterface
+   *   The workflow entity.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if the transition does not exist.
+   */
+  public function setTransitionWeight($transition_id, $weight);
+
+  /**
+   * Sets a transition's from states.
+   *
+   * @param string $transition_id
+   *   The transition ID.
+   * @param array $from_state_ids
+   *   The state IDs to transition from.
+   *
+   * @return \Drupal\Core\Workflow\WorkflowInterface
+   *   The workflow entity.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if the transition does not exist or the states do not exist.
+   */
+  public function setTransitionFromStates($transition_id, array $from_state_ids);
+
+  /**
+   * Deletes a transition.
+   *
+   * @param string $transition_id
+   *   The transition ID.
+   *
+   * @return \Drupal\Core\Workflow\WorkflowInterface
+   *   The workflow entity.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if the transition does not exist.
+   */
+  public function deleteTransition($transition_id);
+
+  /**
+   * Gets the workflow type plugin.
+   *
+   * @return \Drupal\Core\Workflow\WorkflowTypeInterface
+   *   The workflow type plugin.
+   */
+  public function getTypePlugin();
+
+}
diff --git a/core/lib/Drupal/Core/Workflow/WorkflowTypeInterface.php b/core/lib/Drupal/Core/Workflow/WorkflowTypeInterface.php
new file mode 100644
index 0000000..5d5eb23
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/WorkflowTypeInterface.php
@@ -0,0 +1,120 @@
+<?php
+
+namespace Drupal\Core\Workflow;
+
+use Drupal\Component\Plugin\ConfigurablePluginInterface;
+use Drupal\Component\Plugin\DerivativeInspectionInterface;
+use Drupal\Component\Plugin\PluginInspectionInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Session\AccountInterface;
+
+/**
+ * An interface for Workflow type plugins.
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+interface WorkflowTypeInterface extends PluginInspectionInterface, DerivativeInspectionInterface, ConfigurablePluginInterface {
+
+  /**
+   * Gets the label for the workflow type.
+   *
+   * @return string
+   *   The workflow type label.
+   */
+  public function label();
+
+  /**
+   * Performs access checks.
+   *
+   * @param \Drupal\Core\Workflow\WorkflowInterface $entity
+   *   The workflow entity for which to check access.
+   * @param string $operation
+   *   The entity operation. Usually one of 'view', 'view label', 'update' or
+   *   'delete'.
+   * @param \Drupal\Core\Session\AccountInterface $account
+   *   The user for which to check access.
+   *
+   * @return \Drupal\Core\Access\AccessResultInterface
+   *   The access result.
+   */
+  public function checkWorkflowAccess(WorkflowInterface $entity, $operation, AccountInterface $account);
+
+  /**
+   * Decorates states so the WorkflowType can add additional information.
+   *
+   * @param \Drupal\Core\Workflow\StateInterface $state
+   *   The state object to decorate.
+   *
+   * @return \Drupal\Core\Workflow\StateInterface $state
+   *   The decorated state object.
+   */
+  public function decorateState(StateInterface $state);
+
+  /**
+   * React to the removal of a state from a workflow.
+   *
+   * @param string $state_id
+   *   The state ID of the state that is being removed.
+   */
+  public function deleteState($state_id);
+
+  /**
+   * Decorates transitions so the WorkflowType can add additional information.
+   * @param \Drupal\Core\Workflow\TransitionInterface $transition
+   *   The transition object to decorate.
+   *
+   * @return \Drupal\Core\Workflow\TransitionInterface $transition
+   *   The decorated transition object.
+   */
+  public function decorateTransition(TransitionInterface $transition);
+
+  /**
+   * React to the removal of a transition from a workflow.
+   *
+   * @param string $transition_id
+   *   The transition ID of the transition that is being removed.
+   */
+  public function deleteTransition($transition_id);
+
+  /**
+   * Builds a form to be added to the Workflow state edit form.
+   *
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The form state.
+   * @param \Drupal\Core\Workflow\WorkflowInterface $workflow
+   *   The workflow the state is attached to.
+   * @param \Drupal\Core\Workflow\StateInterface|null $state
+   *   The workflow state being edited. If NULL, a new state is being added.
+   *
+   * @return array
+   *   Form elements to add to a workflow state form for customisations to the
+   *   workflow.
+   *
+   * @see \Drupal\workflow_ui\Form\WorkflowStateAddForm::form()
+   * @see \Drupal\workflow_ui\Form\WorkflowStateEditForm::form()
+   */
+  public function buildStateConfigurationForm(FormStateInterface $form_state, WorkflowInterface $workflow, StateInterface $state = NULL);
+
+  /**
+   * Builds a form to be added to the Workflow transition edit form.
+   *
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The form state.
+   * @param \Drupal\Core\Workflow\WorkflowInterface $workflow
+   *   The workflow the state is attached to.
+   * @param \Drupal\Core\Workflow\TransitionInterface|null $transition
+   *   The workflow transition being edited. If NULL, a new transition is being
+   *   added.
+   *
+   * @return array
+   *   Form elements to add to a workflow transition form for customisations to
+   *   the workflow.
+   *
+   * @see \Drupal\workflow_ui\Form\WorkflowTransitionAddForm::form()
+   * @see \Drupal\workflow_ui\Form\WorkflowTransitionEditForm::form()
+   */
+  public function buildTransitionConfigurationForm(FormStateInterface $form_state, WorkflowInterface $workflow, TransitionInterface $transition = NULL);
+
+}
diff --git a/core/lib/Drupal/Core/Workflow/WorkflowTypeManager.php b/core/lib/Drupal/Core/Workflow/WorkflowTypeManager.php
new file mode 100644
index 0000000..58ce7a7
--- /dev/null
+++ b/core/lib/Drupal/Core/Workflow/WorkflowTypeManager.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace Drupal\Core\Workflow;
+
+use Drupal\Core\Cache\CacheBackendInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Plugin\DefaultPluginManager;
+use Drupal\Core\Workflow\Annotation\WorkflowType;
+
+/**
+ * Provides a Workflow type plugin manager.
+ *
+ * @see \Drupal\Core\Workflow\Annotation\WorkflowType
+ * @see \Drupal\Core\Workflow\WorkflowTypeInterface
+ * @see plugin_api
+ *
+ * @internal
+ *   The workflow system is currently experimental and should only be leveraged
+ *   by experimental modules and development releases of contributed modules.
+ */
+class WorkflowTypeManager extends DefaultPluginManager {
+
+  /**
+   * Constructs a new class instance.
+   *
+   * @param \Traversable $namespaces
+   *   An object that implements \Traversable which contains the root paths
+   *   keyed by the corresponding namespace to look for plugin implementations.
+   * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
+   *   Cache backend instance to use.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler to invoke the alter hook with.
+   */
+  public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
+    parent::__construct('Plugin/WorkflowType', $namespaces, $module_handler, WorkflowTypeInterface::class, WorkflowType::class);
+    $this->alterInfo('workflow_type_info');
+    $this->setCacheBackend($cache_backend, 'workflow_type_info');
+  }
+
+}