diff --git a/doc/schema.md b/doc/schema.md
index b4f2c3d..05f8560 100644
--- a/doc/schema.md
+++ b/doc/schema.md
@@ -169,7 +169,7 @@ const VALUE_SCHEMA = [
   "" => "nature du schéma: scalar",
   "name" => "identifiant de la valeur",
   # spécifique à VALUE_SCHEMA
-  "key" => "chemin de clé de la valeur dans le tableau associatif",
+  "pkey" => "chemin de clé de la valeur dans le tableau associatif",
   "header" => "nom de l'en-tête s'il faut présenter cette donnée dans un tableau",
   "composite" => "ce champ fait-il partie d'une valeur composite?",
 ];
@@ -186,7 +186,7 @@ const VALUE_SCHEMA = [
     "desc" => "description de la valeur",
     "name" => "identifiant de la valeur",
     # spécifique à VALUE_SCHEMA
-    "key" => "chemin de clé de la valeur dans le tableau associatif",
+    "pkey" => "chemin de clé de la valeur dans le tableau associatif",
   ],
 ];
 ~~~
@@ -202,7 +202,7 @@ const VALUE_SCHEMA = [
     "desc" => "description de la valeur",
     "name" => "identifiant de la valeur",
     # spécifique à VALUE_SCHEMA
-    "key" => "chemin de clé de la valeur dans le tableau associatif",
+    "pkey" => "chemin de clé de la valeur dans le tableau associatif",
   ],
 ];
 ~~~
diff --git a/src/schema/ScalarSchema.php b/src/schema/ScalarSchema.php
index c74c0f9..868ea69 100644
--- a/src/schema/ScalarSchema.php
+++ b/src/schema/ScalarSchema.php
@@ -5,6 +5,12 @@ use nulib\cl;
 use nur\sery\schema\input\Input;
 use nur\sery\schema\ref\ref_schema;
 use nur\sery\schema\ref\ref_types;
+use nur\sery\schema\types\tarray;
+use nur\sery\schema\types\tbool;
+use nur\sery\schema\types\tcallable;
+use nur\sery\schema\types\tcontent;
+use nur\sery\schema\types\tpkey;
+use nur\sery\schema\types\tstring;
 use nur\sery\schema\values\IValue;
 use nur\sery\schema\values\ScalarValue;
 
@@ -26,6 +32,9 @@ use nur\sery\schema\values\ScalarValue;
  * @property-read mixed $format
  * @property-read array $nature
  * @property-read string|int|null $name
+ * @property-read string|array|null $pkey
+ * @property-read string|null $header
+ * @property-read bool|null $composite
  */
 class ScalarSchema extends Schema {
   /** @var array meta-schema d'un schéma de nature scalaire */
@@ -34,7 +43,7 @@ class ScalarSchema extends Schema {
     "type", "default", "title", "required", "nullable", "desc",
     "analyzer_func", "extractor_func", "parser_func", "normalizer_func", "messages",
     "formatter_func", "format",
-    "", "name", "key", "header", "composite",
+    "", "name", "pkey", "header", "composite",
   ];
 
   /**
@@ -68,18 +77,18 @@ class ScalarSchema extends Schema {
     return $haveIndex0 && $count > 1;
   }
 
-  static function normalize($definition): array {
+  static function normalize($definition, $definitionKey=null): array {
     if (!is_array($definition)) $definition = [$definition];
     # s'assurer que toutes les clés existent avec leur valeur par défaut
     $index = 0;
-    foreach (self::METASCHEMA_KEYS as $key) {
-      if (!array_key_exists($key, $definition)) {
+    foreach (self::METASCHEMA_KEYS as $pkey) {
+      if (!array_key_exists($pkey, $definition)) {
         if (array_key_exists($index, $definition)) {
-          $definition[$key] = $definition[$index];
+          $definition[$pkey] = $definition[$index];
           unset($definition[$index]);
           $index++;
         } else {
-          $definition[$key] = self::METASCHEMA[$key][1];
+          $definition[$pkey] = self::METASCHEMA[$pkey][1];
         }
       }
     }
@@ -87,10 +96,10 @@ class ScalarSchema extends Schema {
     if (cl::have_num_keys($definition)) {
       $keys = array_keys($definition);
       $index = 0;
-      foreach ($keys as $key) {
-        if (!is_int($key)) continue;
-        $definition[$index] = $definition[$key];
-        unset($definition[$key]);
+      foreach ($keys as $pkey) {
+        if (!is_int($pkey)) continue;
+        $definition[$index] = $definition[$pkey];
+        unset($definition[$pkey]);
         $index++;
       }
     }
@@ -127,35 +136,36 @@ class ScalarSchema extends Schema {
     $definition["nullable"] = $nullable;
     # nature
     $nature = $definition[""];
-    self::ensure_array($nature);
+    tarray::ensure_array($nature);
     if (!array_key_exists(0, $nature) || $nature[0] !== "scalar") {
       throw SchemaException::invalid_schema("expected scalar nature");
     }
     $definition[""] = $nature;
-    # name, key, header
+    # name, pkey, header
     $name = $definition["name"];
-    $key = $definition["key"];
+    $pkey = $definition["pkey"];
     $header = $definition["header"];
-    self::ensure_nstring($name);
-    self::ensure_npkey($key);
-    self::ensure_nstring($header);
-    if ($key === null) $key = $name;
+    if ($name === null) $name = $definitionKey;
+    tstring::ensure_nstring($name);
+    tpkey::ensure_npkey($pkey);
+    tstring::ensure_nstring($header);
+    if ($pkey === null) $pkey = $name;
     if ($header === null) $header = $name;
     $definition["name"] = $name;
-    $definition["key"] = $key;
+    $definition["pkey"] = $pkey;
     $definition["header"] = $header;
     # autres éléments
-    self::ensure_nstring($definition["title"]);
-    self::ensure_bool($definition["required"]);
-    self::ensure_bool($definition["nullable"]);
-    self::ensure_ncontent($definition["desc"]);
-    self::ensure_ncallable($definition["analyzer_func"]);
-    self::ensure_ncallable($definition["extractor_func"]);
-    self::ensure_ncallable($definition["parser_func"]);
-    self::ensure_ncallable($definition["normalizer_func"]);
-    self::ensure_narray($definition["messages"]);
-    self::ensure_ncallable($definition["formatter_func"]);
-    self::ensure_nbool($definition["composite"]);
+    tstring::ensure_nstring($definition["title"]);
+    tbool::ensure_bool($definition["required"]);
+    tbool::ensure_bool($definition["nullable"]);
+    tcontent::ensure_ncontent($definition["desc"]);
+    tcallable::ensure_ncallable($definition["analyzer_func"]);
+    tcallable::ensure_ncallable($definition["extractor_func"]);
+    tcallable::ensure_ncallable($definition["parser_func"]);
+    tcallable::ensure_ncallable($definition["normalizer_func"]);
+    tarray::ensure_narray($definition["messages"]);
+    tcallable::ensure_ncallable($definition["formatter_func"]);
+    tbool::ensure_nbool($definition["composite"]);
     return $definition;
   }
 
@@ -175,4 +185,16 @@ class ScalarSchema extends Schema {
     else $input = new Input($value);
     return new ScalarValue($input, $this, $key);
   }
+
+  #############################################################################
+  # key & properties
+
+  const _PROPERTY_PKEYS = [
+    "analyzerFunc" => "analyzer_func",
+    "extractorFunc" => "extractor_func",
+    "parserFunc" => "parser_func",
+    "normalizerFunc" => "normalizer_func",
+    "formatterFunc" => "formatter_func",
+    "nature" => ["", 0],
+  ];
 }
diff --git a/src/schema/Schema.php b/src/schema/Schema.php
index 1697dff..7349e81 100644
--- a/src/schema/Schema.php
+++ b/src/schema/Schema.php
@@ -1,10 +1,13 @@
 <?php
 namespace nur\sery\schema;
 
+use ArrayAccess;
+use BadMethodCallException;
+use LogicException;
 use nulib\cl;
 use nur\sery\schema\values\IValue;
 
-abstract class Schema {
+abstract class Schema implements ArrayAccess {
   /**
    * créer si besoin une nouvelle instance à partir d'une définition de schéma
    */
@@ -23,54 +26,6 @@ abstract class Schema {
     return $md;
   }
 
-  protected static function ensure_string(&$string): void {
-    if (!is_string($string)) $string = strval($string);
-  }
-  protected static function ensure_nstring(&$string): void {
-    if ($string !== null) self::ensure_string($string);
-  }
-  protected static function ensure_bool(&$bool): void {
-    if (!is_bool($bool)) $bool = boolval($bool);
-  }
-  protected static function ensure_nbool(&$bool): void {
-    if ($bool !== null) self::ensure_bool($bool);
-  }
-  protected static function ensure_callable(&$callable): void {
-    if (!is_callable($callable)) throw SchemaException::invalid_callable($callable);
-  }
-  protected static function ensure_ncallable(&$callable): void {
-    if ($callable !== null) self::ensure_callable($callable);
-  }
-  protected static function ensure_array(&$array): void {
-    if (!is_array($array)) $array = cl::with($array);
-  }
-  protected static function ensure_narray(&$array): void {
-    if ($array !== null) self::ensure_array($array);
-  }
-  protected static function ensure_key(&$key): void {
-    if (!is_string($key) && !is_int($key)) $key = strval($key);
-  }
-  protected static function ensure_nkey(&$key): void {
-    if ($key !== null) self::ensure_key($key);
-  }
-  protected static function ensure_pkey(&$pkey): void {
-    if (!is_string($pkey) && !is_int($pkey) && !is_array($pkey)) $pkey = strval($pkey);
-    if (is_array($pkey)) {
-      foreach ($pkey as &$key) {
-        self::ensure_key($key);
-      }; unset($key);
-    }
-  }
-  protected static function ensure_npkey(&$pkey): void {
-    if ($pkey !== null) self::ensure_pkey($pkey);
-  }
-  protected static function ensure_content(&$content): void {
-    if (!is_string($content) && !is_array($content)) $content = strval($content);
-  }
-  protected static function ensure_ncontent(&$content): void {
-    if ($content !== null) self::ensure_content($content);
-  }
-
   /**
    * @var array définition du schéma, à redéfinir le cas échéant dans une classe
    * dérivée
@@ -88,4 +43,28 @@ abstract class Schema {
   function isScalar(?ScalarSchema &$scalar=null): bool { return false; }
 
   abstract function getValue(&$value, $key=null): IValue;
+
+
+  #############################################################################
+  # key & properties
+
+  function offsetExists($offset): bool {
+    return array_key_exists($offset, $this->definition);
+  }
+  function offsetGet($offset) {
+    if (!array_key_exists($offset, $this->definition)) return null;
+    else return $this->definition[$offset];
+  }
+  function offsetSet($offset, $value): void {
+    throw new LogicException("read-only");
+  }
+  function offsetUnset($offset): void {
+    throw new LogicException("read-only");
+  }
+
+  const _PROPERTY_PKEYS = [];
+  function __get($name) {
+    $pkey = cl::get(static::_PROPERTY_PKEYS, $name, $name);
+    return cl::pget($this->definition, $pkey);
+  }
 }
diff --git a/src/schema/input/FormInput.php b/src/schema/input/FormInput.php
index f41f75e..5a48b4d 100644
--- a/src/schema/input/FormInput.php
+++ b/src/schema/input/FormInput.php
@@ -1,12 +1,15 @@
 <?php
 namespace nur\sery\schema\input;
 
+#XXX implémenter le renommage de paramètres et faire des méthodes pour
+# construire des querystring et paramètres de formulaires
 /**
  * Class FormInput: accès à des paramètres de formulaire (POST ou GET, dans cet
  * ordre)
  *
  * cette implémentation lit depuis les paramètres de formulaire et écrit dans
  * une référence
+ *
  */
 class FormInput extends Input {
   function exists($key=null): bool {
diff --git a/src/schema/input/GetInput.php b/src/schema/input/GetInput.php
index 2db7f9c..aa0c8c4 100644
--- a/src/schema/input/GetInput.php
+++ b/src/schema/input/GetInput.php
@@ -7,7 +7,7 @@ namespace nur\sery\schema\input;
  * cette implémentation lit depuis les paramètres de formulaire et écrit dans
  * une référence
  */
-class GetInput extends Input {
+class GetInput extends FormInput {
   function exists($key=null): bool {
     if ($key === null) return false;
     return array_key_exists($key, $_GET);
diff --git a/src/schema/input/PostInput.php b/src/schema/input/PostInput.php
index ff4d875..80f2b22 100644
--- a/src/schema/input/PostInput.php
+++ b/src/schema/input/PostInput.php
@@ -7,7 +7,7 @@ namespace nur\sery\schema\input;
  * cette implémentation lit depuis les paramètres de formulaire et écrit dans
  * une référence
  */
-class PostInput extends Input {
+class PostInput extends FormInput {
   function exists($key=null): bool {
     if ($key === null) return false;
     return array_key_exists($key, $_POST);
diff --git a/src/schema/ref/ref_schema.php b/src/schema/ref/ref_schema.php
index 1d72ad2..3d7f2de 100644
--- a/src/schema/ref/ref_schema.php
+++ b/src/schema/ref/ref_schema.php
@@ -5,7 +5,7 @@ class ref_schema {
   /** @var array schéma des natures de schéma */
   const NATURE_METASCHEMA = [
     "nature" => ["string", null, "nature du schéma",
-      "key" => 0,
+      "pkey" => 0,
       "allowed_values" => ["assoc", "list", "scalar"],
     ],
     "title" => ["?string", null, "libellé de la valeur"],
@@ -35,7 +35,7 @@ class ref_schema {
       "" => ["assoc", "schema" => self::NATURE_METASCHEMA],
     ],
     "name" => ["?string", null, "identifiant de la valeur"],
-    "key" => ["?pkey", null, "chemin de clé de la valeur dans un tableau associatif"],
+    "pkey" => ["?pkey", null, "chemin de clé de la valeur dans un tableau associatif"],
     "header" => ["?string", null, "nom de l'en-tête s'il faut présenter cette donnée dans un tableau"],
     "composite" => ["?bool", null, "ce champ fait-il partie d'une valeur composite?"],
   ];
diff --git a/src/schema/types/tarray.php b/src/schema/types/tarray.php
new file mode 100644
index 0000000..1112609
--- /dev/null
+++ b/src/schema/types/tarray.php
@@ -0,0 +1,14 @@
+<?php
+namespace nur\sery\schema\types;
+
+use nulib\cl;
+
+class tarray {
+  static function ensure_array(&$array): void {
+    if (!is_array($array)) $array = cl::with($array);
+  }
+
+  static function ensure_narray(&$array): void {
+    if ($array !== null) self::ensure_array($array);
+  }
+}
diff --git a/src/schema/types/tbool.php b/src/schema/types/tbool.php
new file mode 100644
index 0000000..84e0313
--- /dev/null
+++ b/src/schema/types/tbool.php
@@ -0,0 +1,12 @@
+<?php
+namespace nur\sery\schema\types;
+
+class tbool {
+  static function ensure_bool(&$bool): void {
+    if (!is_bool($bool)) $bool = boolval($bool);
+  }
+
+  static function ensure_nbool(&$bool): void {
+    if ($bool !== null) self::ensure_bool($bool);
+  }
+}
diff --git a/src/schema/types/tcallable.php b/src/schema/types/tcallable.php
new file mode 100644
index 0000000..094a772
--- /dev/null
+++ b/src/schema/types/tcallable.php
@@ -0,0 +1,14 @@
+<?php
+namespace nur\sery\schema\types;
+
+use nur\sery\schema\SchemaException;
+
+class tcallable {
+  static function ensure_callable(&$callable): void {
+    if (!is_callable($callable)) throw SchemaException::invalid_callable($callable);
+  }
+
+  static function ensure_ncallable(&$callable): void {
+    if ($callable !== null) self::ensure_callable($callable);
+  }
+}
diff --git a/src/schema/types/tcontent.php b/src/schema/types/tcontent.php
new file mode 100644
index 0000000..c56ebec
--- /dev/null
+++ b/src/schema/types/tcontent.php
@@ -0,0 +1,12 @@
+<?php
+namespace nur\sery\schema\types;
+
+class tcontent {
+  static function ensure_content(&$content): void {
+    if (!is_string($content) && !is_array($content)) $content = strval($content);
+  }
+
+  static function ensure_ncontent(&$content): void {
+    if ($content !== null) self::ensure_content($content);
+  }
+}
diff --git a/src/schema/types/tkey.php b/src/schema/types/tkey.php
new file mode 100644
index 0000000..b4bd9a3
--- /dev/null
+++ b/src/schema/types/tkey.php
@@ -0,0 +1,12 @@
+<?php
+namespace nur\sery\schema\types;
+
+class tkey {
+  static function ensure_key(&$key): void {
+    if (!is_string($key) && !is_int($key)) $key = strval($key);
+  }
+
+  static function ensure_nkey(&$key): void {
+    if ($key !== null) self::ensure_key($key);
+  }
+}
diff --git a/src/schema/types/tpkey.php b/src/schema/types/tpkey.php
new file mode 100644
index 0000000..a85154f
--- /dev/null
+++ b/src/schema/types/tpkey.php
@@ -0,0 +1,18 @@
+<?php
+namespace nur\sery\schema\types;
+
+class tpkey {
+  static function ensure_pkey(&$pkey): void {
+    if (!is_string($pkey) && !is_int($pkey) && !is_array($pkey)) $pkey = strval($pkey);
+    if (is_array($pkey)) {
+      foreach ($pkey as &$key) {
+        tkey::ensure_key($key);
+      };
+      unset($key);
+    }
+  }
+
+  static function ensure_npkey(&$pkey): void {
+    if ($pkey !== null) self::ensure_pkey($pkey);
+  }
+}
diff --git a/src/schema/types/tstring.php b/src/schema/types/tstring.php
new file mode 100644
index 0000000..6d95b24
--- /dev/null
+++ b/src/schema/types/tstring.php
@@ -0,0 +1,12 @@
+<?php
+namespace nur\sery\schema\types;
+
+class tstring {
+  static function ensure_string(&$string): void {
+    if (!is_string($string)) $string = strval($string);
+  }
+
+  static function ensure_nstring(&$string): void {
+    if ($string !== null) self::ensure_string($string);
+  }
+}