diff --git a/src/node.xsl b/src/node.xsl
index 938e7c1..2e07a75 100644
--- a/src/node.xsl
+++ b/src/node.xsl
@@ -47,7 +47,9 @@
   functional system.
 
   @menu
-  * Primitive Constructors:: Functional equivalents of XSLT node primitives
+  * Primitive Constructors::      Functional equivalents of XSLT node
+                                    primitives
+  * Mutators: Node Mutators.      Functional node manipulation
   @end menu
 
 
@@ -195,4 +197,34 @@
   <sequence select="$comment" />
 </function>
 
+
+<!--
+  @node Node Mutators
+  @section Node Mutators
+
+  A @dfn{node mutator} produces an altered copy of an existing node.
+-->
+
+<!--
+  Create a copy of @var{element} with additional attributes defined by
+    @var{attrs},
+    replacing attributes that already exist with the same QName.
+
+  Attributes that already exist on @var{element} but are not specified in
+    @var{attrs} will be left untouched.
+  All child nodes of @var{element} are retained by reference.
+-->
+<function name="n:add-attributes" as="element()">
+  <param name="element" as="element()" />
+  <param name="attrs"   as="attribute()*" />
+
+  <sequence select="if ( empty( $attrs ) ) then
+                        $element
+                      else
+                        n:element( node-name( $element ),
+                                   ( $element/@*,
+                                     $attrs ),
+                                   $element/node() )" />
+</function>
+
 </stylesheet>
diff --git a/test/node.xspec b/test/node.xspec
index e89f87d..2b53733 100644
--- a/test/node.xspec
+++ b/test/node.xspec
@@ -34,6 +34,13 @@
             select="QName( 'test-ns-b', 'test-prefix-b:b' )" />
   <variable name="test-qname-c"
             select="QName( 'test-ns-c', 'test-prefix-c:c' )" />
+  <variable name="test-qname-d"
+            select="QName( 'test-ns-d', 'test-prefix-d:d' )" />
+  <variable name="test-qname-e"
+            select="QName( 'test-ns-e', 'test-prefix-e:e' )" />
+
+  <variable name="test-qname-noprefix"
+            select="QName( 'test-ns-a', 'a' )" />
 
   <variable name="test-node-element" as="element()">
     <foo:node-a foo="bar">
@@ -55,6 +62,10 @@
             select="5" />
 
 
+  <!--
+    Primitives
+  -->
+
   <scenario label="A new element">
     <scenario label="with only a QName">
       <call function="n:element">
@@ -261,4 +272,113 @@
               test="count( $x:result/node() ) = 3" />
     </scenario>
   </scenario>
+
+
+  <!--
+    Node Mutators
+  -->
+
+  <scenario label="Mutator">
+    <scenario label="n:add-attributes">
+      <variable name="element-attr-ns" as="element()"
+                select="n:element( $test-qname-a,
+                                   ( n:attr( $test-qname-b, 'b' ),
+                                     n:attr( $test-qname-c, 'c' ) ),
+                                   ( n:element( $test-qname-b ),
+                                     n:element( $test-qname-c ) ) )" />
+
+      <scenario label="with no new attributes">
+        <call function="n:add-attributes">
+          <param name="element" select="$element-attr-ns" />
+          <param name="attrs"   select="()" />
+        </call>
+
+        <expect label="produces node with same QName"
+                test="node-name( $x:result ) = $test-qname-a" />
+
+        <expect label="retains all existing attributes"
+                test="deep-equal( $x:result/@*,
+                                  $element-attr-ns/@* )" />
+
+        <expect label="retains all existing children"
+                test="deep-equal( $x:result/node(),
+                                  $element-attr-ns/node() )" />
+      </scenario>
+
+
+      <scenario label="with all new attributes">
+        <call function="n:add-attributes">
+          <param name="element"    select="$element-attr-ns" />
+          <param name="attrs"
+                 select="( n:attr( $test-qname-d, 'd' ),
+                           n:attr( $test-qname-e, 'e' ) )" />
+        </call>
+
+        <expect label="produces node with same QName"
+                test="node-name( $x:result ) = $test-qname-a" />
+
+        <expect label="adds new attributes"
+                test="( some $x in $x:result/@* satisfies
+                        ( node-name( $x ) = $test-qname-d
+                          and $x = 'd' ) )
+                      and ( some $x in $x:result/@* satisfies
+                            ( node-name( $x ) = $test-qname-e
+                              and $x = 'e' ) )" />
+
+        <expect label="retains all existing attributes"
+                test="( some $x in $x:result/@* satisfies
+                        ( node-name( $x ) = $test-qname-b
+                          and $x = 'b' ) )
+                      and ( some $x in $x:result/@* satisfies
+                            ( node-name( $x ) = $test-qname-c
+                              and $x = 'c' ) )" />
+
+        <!-- less than check will allow this to succeed even if an above
+             test fails so that we can accurately determine the problem-->
+        <expect label="does not add any other attributes"
+                test="count( $x:result/@* ) &lt;= 4" />
+
+        <expect label="retains all existing children"
+                test="deep-equal( $x:result/node(),
+                                  $element-attr-ns/node() )" />
+      </scenario>
+
+
+      <scenario label="with some duplicate attributes">
+        <call function="n:add-attributes">
+          <param name="element"    select="$element-attr-ns" />
+          <param name="attrs"
+                 select="( n:attr( $test-qname-c, 'c2' ),
+                           n:attr( $test-qname-d, 'd2' ) )" />
+        </call>
+
+        <expect label="produces node with same QName"
+                test="node-name( $x:result ) = $test-qname-a" />
+
+        <expect label="adds new attributes"
+                test="( some $x in $x:result/@* satisfies
+                        ( node-name( $x ) = $test-qname-d
+                          and $x = 'd2' ) )" />
+
+        <expect label="replaces existing attributes"
+                test="( some $x in $x:result/@* satisfies
+                        ( node-name( $x ) = $test-qname-c
+                          and $x = 'c2' ) )" />
+
+        <expect label="retains all existing attributes"
+                test="( some $x in $x:result/@* satisfies
+                        ( node-name( $x ) = $test-qname-b
+                          and $x = 'b' ) )" />
+
+        <!-- less than check will allow this to succeed even if an above
+             test fails so that we can accurately determine the problem-->
+        <expect label="does not add any other attributes"
+                test="count( $x:result/@* ) &lt;= 3" />
+
+        <expect label="retains all existing children"
+                test="deep-equal( $x:result/node(),
+                                  $element-attr-ns/node() )" />
+      </scenario>
+    </scenario>
+  </scenario>
 </description>