diff --git a/src/schema/Value.php b/src/schema/Value.php
index c80239b..3d8efd3 100644
--- a/src/schema/Value.php
+++ b/src/schema/Value.php
@@ -59,7 +59,7 @@ abstract class Value implements ArrayAccess, IteratorAggregate {
   abstract function set($value): self;
 
   /** supprimer la valeur */
-  abstract function unset(): void;
+  abstract function unset(): self;
 
   /** formatter la valeur pour affichage */
   abstract function format($format=null): string;
diff --git a/src/schema/_scalar/ScalarValue.php b/src/schema/_scalar/ScalarValue.php
index 84c4355..26d6da0 100644
--- a/src/schema/_scalar/ScalarValue.php
+++ b/src/schema/_scalar/ScalarValue.php
@@ -10,9 +10,10 @@ use nur\sery\schema\types\IType;
 use nur\sery\schema\Value;
 
 class ScalarValue extends Value {
-  function __construct(ScalarSchema $schema, &$dest=null, $destKey=null, bool $defaultVerifix=true) {
+  function __construct(ScalarSchema $schema, &$dest=null, $destKey=null, bool $defaultVerifix=true, bool $defaultThrow=true) {
     $this->schema = $schema;
     $this->defaultVerifix = $defaultVerifix;
+    $this->defaultThrow = $defaultThrow;
     $this->result = new ScalarResult();
     $this->reset($dest, $destKey);
   }
@@ -31,6 +32,9 @@ class ScalarValue extends Value {
   /** @var bool */
   protected $defaultVerifix;
 
+  /** @var bool */
+  protected $defaultThrow;
+
   /** @var IType type de la valeur après analyse */
   protected $type;
 
@@ -44,7 +48,7 @@ class ScalarValue extends Value {
     $this->destKey = $destKey;
     $this->type = null;
     $this->_analyze();
-    if ($verifix === null) $verifix = $this->defaultVerifix;
+    if ($verifix == null) $verifix = $this->defaultVerifix;
     if ($verifix) $this->verifix();
     return $this;
   }
@@ -89,16 +93,12 @@ class ScalarValue extends Value {
     else return $result->setInvalid($schema);
   }
 
-  /**
-   * analyser, corriger éventuellement et normaliser la valeur
-   *
-   * si la valeur était déjà normalisée, retourner false.
-   */
-  function verifix(bool $throw=true): bool {
+  function verifix(?bool $throw=null): bool {
     $type = $this->getType();
     $destKey = $this->destKey;
     $value = $this->input->get($destKey);
     $modified = $type->verifix($value, $this->result);
+    if ($throw === null) $throw = $this->defaultThrow;
     if ($this->result->valid) $this->input->set($value, $destKey);
     else $this->result->throw($throw);
     return $modified;
@@ -141,11 +141,12 @@ class ScalarValue extends Value {
     return $this;
   }
 
-  function unset(?bool $verifix=null): void {
+  function unset(?bool $verifix=null): Value {
     $this->input->unset($this->destKey);
     $this->_analyze();
     if ($verifix === null) $verifix = $this->defaultVerifix;
     if ($verifix) $this->verifix();
+    return $this;
   }
 
   function format($format=null): string {
diff --git a/src/schema/types/IType.php b/src/schema/types/IType.php
index 73dc77f..c9a043a 100644
--- a/src/schema/types/IType.php
+++ b/src/schema/types/IType.php
@@ -8,15 +8,25 @@ use nur\sery\schema\Result;
  * Interface IType: un type de données
  */
 interface IType {
-  function canAnalyze(Input $input, $desyKey): bool;
+  /** ce type peut-il analyser la donnée dans $input[$destKey] ? */
+  function canAnalyze(Input $input, $destKey): bool;
 
-  function isAvailable(Input $input, $desyKey): bool;
+  /** la donnée $input[$destKey] est-elle disponible? */
+  function isAvailable(Input $input, $destKey): bool;
 
+  /** la valeur $value est-elle nulle? */
   function isNull($value): bool;
 
+  /** la valeur $value est-elle valide et normalisée le cas échéant? */
   function isValid($value, ?bool &$normalized=null): bool;
 
-  function verifix(&$value, ?Result &$result): bool;
+  /**
+   * analyser, corriger éventuellement et normaliser la valeur
+   *
+   * si la valeur était déjà normalisée, retourner false.
+   */
+  function verifix(&$value, Result &$result): bool;
 
-  function format($value, $format=null);
+  /** formatter la valeur pour affichage */
+  function format($value, $format=null): string;
 }