diff --git a/src/Context/ContextDefinition.php b/src/Context/ContextDefinition.php
index 7122d6ec..722eb8d0 100644
--- a/src/Context/ContextDefinition.php
+++ b/src/Context/ContextDefinition.php
@@ -117,4 +117,46 @@ class ContextDefinition extends ContextDefinitionCore implements ContextDefiniti
     return $this;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getWidgetId($dataType) {
+    $widgets = [
+      'text_input' => [
+        'boolean',
+        'datetime',
+        'duration',
+        'email',
+        'entity_reference',
+        'float',
+        'integer',
+        'link',
+        'string',
+        'url',
+      ],
+      'textarea' => [
+        'list',
+        'daterange',
+      ],
+    ];
+
+    foreach ($widgets as $widget_id => $data_types) {
+      foreach ($data_types as $data_type) {
+        if ($dataType == $data_type) {
+          return $widget_id;
+        }
+      }
+    }
+
+    // If we don't recognize the data type, use the "broken" widget.
+    return 'broken';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getWidgetSettings() {
+    return [];
+  }
+
 }
diff --git a/src/Context/ContextDefinitionInterface.php b/src/Context/ContextDefinitionInterface.php
index 118627ca..b65649b1 100644
--- a/src/Context/ContextDefinitionInterface.php
+++ b/src/Context/ContextDefinitionInterface.php
@@ -68,4 +68,24 @@ interface ContextDefinitionInterface extends ContextDefinitionInterfaceCore {
    */
   public function toArray();
 
+  /**
+   * Gets default widget id.
+   *
+   * @param string $dataType
+   *   The data type of the field.
+   *
+   * @return string|null
+   *   A string with the widget id or nothing if the data type needed by
+   *   the context is not supported by any widget.
+   */
+  public function getWidgetId($dataType);
+
+  /**
+   * Gets default configuration of the widget.
+   *
+   * @return array
+   *   An associative array with the default configuration.
+   */
+  public function getWidgetSettings();
+
 }
diff --git a/src/Context/ContextHandlerTrait.php b/src/Context/ContextHandlerTrait.php
index ecea07d1..3787d548 100644
--- a/src/Context/ContextHandlerTrait.php
+++ b/src/Context/ContextHandlerTrait.php
@@ -90,7 +90,7 @@ trait ContextHandlerTrait {
         // If a context mapping has been specified, the value might end up NULL
         // but valid (e.g. a reference on an empty property). In that case
         // isAllowedNull determines whether the context is conform.
-        if (!isset($this->configuration['context_mapping'][$name])) {
+        if (!isset($this->configuration['context_mapping']) || !isset($this->configuration['context_mapping'][$name])) {
           throw new EvaluationException("Required context $name is missing for plugin "
             . $plugin->getPluginId() . '.');
         }
@@ -191,7 +191,7 @@ trait ContextHandlerTrait {
    *   invalid.
    */
   protected function getMappedDefinition($context_name, ExecutionMetadataStateInterface $metadata_state) {
-    if (isset($this->configuration['context_mapping'][$context_name])) {
+    if (isset($this->configuration['context_mapping']) && isset($this->configuration['context_mapping'][$context_name])) {
       return $metadata_state->fetchDefinitionByPropertyPath($this->configuration['context_mapping'][$context_name]);
     }
   }
@@ -269,10 +269,12 @@ trait ContextHandlerTrait {
 
     // Reverse the mapping and apply the changes.
     foreach ($changed_definitions as $context_name => $definition) {
-      $selector = $this->configuration['context_mapping'][$context_name];
-      // @todo Deal with selectors matching not a context name.
-      if (strpos($selector, '.') === FALSE) {
-        $metadata_state->setDataDefinition($selector, $definition);
+      if (isset($this->configuration['context_mapping'])) {
+        $selector = $this->configuration['context_mapping'][$context_name];
+        // @todo: Deal with selectors matching not a context name.
+        if (strpos($selector, '.') === FALSE) {
+          $metadata_state->setDataDefinition($selector, $definition);
+        }
       }
     }
   }
diff --git a/src/Form/ContextFormTrait.php b/src/Form/ContextFormTrait.php
new file mode 100644
index 00000000..51d6e7e2
--- /dev/null
+++ b/src/Form/ContextFormTrait.php
@@ -0,0 +1,180 @@
+<?php
+
+namespace Drupal\rules\Form;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Form\SubformState;
+use Drupal\rules\Context\ContextConfig;
+// TODO Question: should we do this change?
+use Drupal\rules\Context\ContextDefinitionInterface;
+use Drupal\rules\Context\DataProcessorManagerTrait;
+use Drupal\typed_data\Widget\FormWidgetManagerTrait;
+
+/**
+ * Provides form logic for handling contexts when configuring an expression.
+ */
+trait ContextFormTrait {
+
+  use DataProcessorManagerTrait;
+  use FormWidgetManagerTrait;
+
+  /**
+   * Provides the form part for a context parameter.
+   */
+  public function buildContextForm(array $form, FormStateInterface $form_state, $context_name, ContextDefinitionInterface $context_definition, array $configuration) {
+    $form['context'][$context_name] = [
+      '#type' => 'fieldset',
+      '#title' => $context_definition->getLabel(),
+    ];
+    $form['context'][$context_name]['description'] = [
+      '#markup' => $context_definition->getDescription(),
+    ];
+
+    // If the form has been submitted already take the mode from the submitted
+    // values, otherwise default to existing configuration. And if that does not
+    // exist default to the "input" mode.
+    $mode = $form_state->get('context_' . $context_name);
+    if (!$mode) {
+      if (isset($configuration['context_mapping']) && isset($configuration['context_mapping'][$context_name])) {
+        $mode = 'selector';
+      }
+      else {
+        $mode = 'input';
+      }
+      $form_state->set('context_' . $context_name, $mode);
+    }
+
+    $title = $mode == 'selector' ? $this->t('Data selector') : $this->t('Value');
+
+    if (isset($configuration['context_values'][$context_name])) {
+      $default_value = $configuration['context_values'][$context_name];
+    }
+    elseif (isset($configuration['context_mapping']) && isset($configuration['context_mapping'][$context_name])) {
+      $default_value = $configuration['context_mapping'][$context_name];
+    }
+    else {
+      $default_value = $context_definition->getDefaultValue();
+    }
+
+    $form['context'][$context_name]['setting'] = [
+      '#type' => 'textarea',
+      '#title' => $title,
+      '#required' => $context_definition->isRequired(),
+      '#default_value' => $default_value,
+    ];
+
+    // Use suitable widgets for data entry of values.
+    if ($context_name == 'value') {
+      $dataManager = $context_definition->getTypedDataManager();
+      $dataDefinition = $context_definition->getDataDefinition();
+      $typed_data = $dataManager->create($dataDefinition);
+
+      if (isset($configuration['context_mapping']) && $property_path = $configuration['context_mapping']['data']) {
+        $sub_paths = explode('.', $property_path);
+        $dataType = \Drupal::entityManager()->getStorage('field_storage_config')->load($sub_paths[0] . '.' . $sub_paths[1])->getType();
+
+        if ($widget_id = $context_definition->getWidgetId($dataType)) {
+          $widget = $this->getFormWidgetManager()->createInstance($widget_id);
+          $sub_form = [];
+          $sub_form_state = SubformState::createForSubform($sub_form, $form, $form_state);
+
+          $form['context'][$context_name]['setting'] = $widget->form($typed_data, $sub_form_state);
+        }
+      }
+    }
+
+    $element = &$form['context'][$context_name]['setting'];
+
+    if ($mode == 'selector') {
+      $element['#type'] = 'textfield';
+      $element['#description'] = $this->t("The data selector helps you drill down into the data available to Rules. <em>To make entity fields appear in the data selector, you may have to use the condition 'entity has field' (or 'content is of type').</em> More useful tips about data selection is available in <a href=':url'>the online documentation</a>.", [
+        ':url' => 'https://www.drupal.org/node/1300042',
+      ]);
+
+      $url = $this->getRulesUiHandler()->getUrlFromRoute('autocomplete', []);
+      $element['#attributes']['class'][] = 'rules-autocomplete';
+      $element['#attributes']['data-autocomplete-path'] = $url->toString();
+      $element['#attached']['library'][] = 'rules/rules.autocomplete';
+    }
+    elseif ($context_definition->isMultiple()) {
+      $element['#type'] = 'textarea';
+      // @todo Get a description for possible values that can be filled in.
+      $element['#description'] = $this->t('Enter one value per line for this multi-valued context.');
+
+      // Glue the list of values together as one item per line in the text area.
+      if (is_array($default_value)) {
+        $element['#default_value'] = implode("\n", $default_value);
+      }
+    }
+
+    $value = $mode == 'selector' ? $this->t('Switch to the direct input mode') : $this->t('Switch to data selection');
+    $form['context'][$context_name]['switch_button'] = [
+      '#type' => 'submit',
+      '#name' => 'context_' . $context_name,
+      '#attributes' => ['class' => ['rules-switch-button']],
+      '#parameter' => $context_name,
+      '#value' => $value,
+      '#submit' => [static::class . '::switchContextMode'],
+      // Do not validate!
+      '#limit_validation_errors' => [],
+    ];
+    return $form;
+  }
+
+  /**
+   * Creates a context config object from the submitted form values.
+   *
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The form state containing the submitted values.
+   * @param \Drupal\Core\Plugin\Context\ContextDefinitionInterface[] $context_definitions
+   *   The context definitions of the plugin.
+   *
+   * @return \Drupal\rules\Context\ContextConfig
+   *   The context config object populated with context mappings/values.
+   */
+  protected function getContextConfigFromFormValues(FormStateInterface $form_state, array $context_definitions) {
+    $context_config = ContextConfig::create();
+    if ($form_state->hasValue('context')) {
+      foreach ($form_state->getValue('context') as $context_name => $value) {
+        if ($form_state->get("context_$context_name") == 'selector') {
+          $context_config->map($context_name, $value['setting']);
+        }
+        else {
+          // Each line of the textarea is one value for 'multiple' contexts.
+          if ($context_definitions[$context_name]->isMultiple()) {
+            // Textareas should always have \r\n line breaks, but for more
+            // robust parsing we should also accommodate just \n or just \r.
+            //
+            // Additionally, we want to remove leading and trailing whitespace
+            // from each line, and discard any empty lines.
+            $values = preg_split('/\s*\R\s*/', $value['setting'], NULL, PREG_SPLIT_NO_EMPTY);
+            $context_config->setValue($context_name, $values);
+          }
+          else {
+            $context_config->setValue($context_name, $value['setting']);
+          }
+          // For now, always add in the token context processor if it's present.
+          // @todo Improve this in https://www.drupal.org/node/2804035.
+          if ($this->getDataProcessorManager()->getDefinition('rules_tokens')) {
+            $context_config->process($context_name, 'rules_tokens');
+          }
+        }
+      }
+    }
+
+    return $context_config;
+  }
+
+  /**
+   * Submit callback: switch a context to data selecor or direct input mode.
+   */
+  public static function switchContextMode(array &$form, FormStateInterface $form_state) {
+    $element_name = $form_state->getTriggeringElement()['#name'];
+    $mode = $form_state->get($element_name);
+    $switched_mode = $mode == 'selector' ? 'input' : 'selector';
+    $form_state->set($element_name, $switched_mode);
+
+    $form_state->setRebuild();
+  }
+
+}
diff --git a/src/Form/Expression/ActionForm.php b/src/Form/Expression/ActionForm.php
index 96d27bca..02be135e 100644
--- a/src/Form/Expression/ActionForm.php
+++ b/src/Form/Expression/ActionForm.php
@@ -6,6 +6,7 @@ use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\rules\Core\RulesActionManagerInterface;
 use Drupal\rules\Engine\ActionExpressionInterface;
+use Drupal\rules\Form\ContextFormTrait;
 use Drupal\rules\Ui\RulesUiHandlerTrait;
 
 /**
@@ -13,9 +14,9 @@ use Drupal\rules\Ui\RulesUiHandlerTrait;
  */
 class ActionForm implements ExpressionFormInterface {
 
-  use ContextFormTrait;
   use StringTranslationTrait;
   use RulesUiHandlerTrait;
+  use ContextFormTrait;
 
   /**
    * The action plugin manager.
diff --git a/src/Form/Expression/ConditionForm.php b/src/Form/Expression/ConditionForm.php
index ee6add0d..9aa2b8ff 100644
--- a/src/Form/Expression/ConditionForm.php
+++ b/src/Form/Expression/ConditionForm.php
@@ -6,6 +6,7 @@ use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\rules\Core\ConditionManager;
 use Drupal\rules\Engine\ConditionExpressionInterface;
+use Drupal\rules\Form\ContextFormTrait;
 use Drupal\rules\Ui\RulesUiHandlerTrait;
 
 /**
@@ -13,9 +14,9 @@ use Drupal\rules\Ui\RulesUiHandlerTrait;
  */
 class ConditionForm implements ExpressionFormInterface {
 
-  use ContextFormTrait;
   use StringTranslationTrait;
   use RulesUiHandlerTrait;
+  use ContextFormTrait;
 
   /**
    * The condition plugin manager.