diff --git a/README b/README
index 0538837..8253952 100644
--- a/README
+++ b/README
@@ -5,9 +5,9 @@ SYNOPSIS
      my $mrdf = MongoDB::RDF->new(
          database => MongoDB::Connection->new(host => 'localhost', port => 27017)->test_rdf
      );
- 
+
      my $graph = $mrdf->default_graph;
- 
+
      my $r = MongoDB::RDF::Resource->new('http://example.org/0');
      $r->dc_title('my title');
      $graph->save($r);
diff --git a/lib/MongoDB/RDF.pm b/lib/MongoDB/RDF.pm
index 21d2a48..34a9660 100644
--- a/lib/MongoDB/RDF.pm
+++ b/lib/MongoDB/RDF.pm
@@ -18,9 +18,9 @@ MongoDB::RDF - Stores RDF-JSON documents in MongoDB.
  my $mrdf = MongoDB::RDF->new(
      database => MongoDB::Connection->new(host => 'localhost', port => 27017)->test_rdf
  );
- 
+
  my $graph = $mrdf->default_graph;
- 
+
  my $r = MongoDB::RDF::Resource->new('http://example.org/0');
  $r->dc_title('my title');
  $graph->save($r);
diff --git a/lib/MongoDB/RDF/Cursor.pm b/lib/MongoDB/RDF/Cursor.pm
index 893414a..9832310 100644
--- a/lib/MongoDB/RDF/Cursor.pm
+++ b/lib/MongoDB/RDF/Cursor.pm
@@ -28,7 +28,7 @@ sub cursor { $_[0]->{cursor} }
 =cut
 
 sub next {
-    my $self = shift;    
+    my $self = shift;
     my $doc = $self->cursor->next;
     return unless $doc;
     return MongoDB::RDF::Resource->_new_from_document($doc);
@@ -104,7 +104,7 @@ TODO explain why it sort by the first value of the predicate.
 
 =cut
 
-sub sort { 
+sub sort {
     my $self = shift;
     my ($order) = @_;
 
diff --git a/lib/MongoDB/RDF/Graph.pm b/lib/MongoDB/RDF/Graph.pm
index 6b87ea5..db9cbb2 100644
--- a/lib/MongoDB/RDF/Graph.pm
+++ b/lib/MongoDB/RDF/Graph.pm
@@ -28,11 +28,11 @@ sub _new {
     my %args = @_;
     my $self = bless {}, $class;
     for (qw(name mrdf)) {
-        die "$_ required" unless $args{$_};    
+        die "$_ required" unless $args{$_};
         $self->{$_} = $args{$_};
     }
     # TODO maintain a global cache of the ensured indexes
-    # the cost of ensure_index may not be negligable 
+    # the cost of ensure_index may not be negligable
     $self->collection->ensure_index({ _subject => 1 }, { unique => 1 });
     $self->ensure_index({ rdf_type => 1 });
     return $self;
@@ -53,7 +53,7 @@ sub name { $_[0]->{name} }
 =head2 $self->load( $uri )
 
 Loads a resource from the graph.
-If this resource has a registered rdf_type, then this resource 
+If this resource has a registered rdf_type, then this resource
 will be reblessed to the corresponding class.
 (See MongoDB::RDF::Resource->register_rdf_type)
 
diff --git a/lib/MongoDB/RDF/Namespace.pm b/lib/MongoDB/RDF/Namespace.pm
index c64e36f..c814887 100644
--- a/lib/MongoDB/RDF/Namespace.pm
+++ b/lib/MongoDB/RDF/Namespace.pm
@@ -30,7 +30,7 @@ sub resolve {
             return $uri.$name;
         }
     }
-    return $local; 
+    return $local;
 }
 
 =head2 register
diff --git a/lib/MongoDB/RDF/Resource.pm b/lib/MongoDB/RDF/Resource.pm
index f3fb2aa..1e23bc3 100644
--- a/lib/MongoDB/RDF/Resource.pm
+++ b/lib/MongoDB/RDF/Resource.pm
@@ -43,7 +43,7 @@ sub new {
     $self->set_subject($subject);
 
     if (my $type = $Class2rdf_type{$class}) {
-        $self->set(rdf_type => $type);    
+        $self->set(rdf_type => $type);
     }
 
     $self->init if $self->can('init');
@@ -59,7 +59,7 @@ Set the subject, if $uri is undef a blank node URI is created.
 =cut
 
 sub set_subject {
-    my $self = shift;    
+    my $self = shift;
     my ($uri) = @_;
     unless ($uri) {
         my $oid = MongoDB::OID->new;
@@ -76,7 +76,7 @@ Returns the subject.
 =cut
 
 sub subject {
-    my $self = shift;    
+    my $self = shift;
     return $self->{document}{_subject};
 }
 
@@ -128,11 +128,11 @@ sub properties {
 # for this reason, if the property has only one element,
 # don't create the array.
 sub _property {
-    my $self = shift;    
+    my $self = shift;
     my ($uri, $values) = @_;
 
     if ($values) {
-        die 'must be an arrayref' unless ref $values eq 'ARRAY';    
+        die 'must be an arrayref' unless ref $values eq 'ARRAY';
         if (@$values == 0) {
                 delete $self->{document}{$uri};
         }
@@ -149,7 +149,7 @@ sub _property {
 
 # object in the "subject predicate object" sense
 sub _value2object {
-    my $self = shift;    
+    my $self = shift;
     my ($value) = @_;
     if (looks_like_uri($value)) {
         return { type => 'uri', value => canonical_uri($value) };
@@ -160,7 +160,7 @@ sub _value2object {
 }
 
 sub _object2value {
-    my $self = shift;    
+    my $self = shift;
     my ($object, $opts) = @_;
     if (my $graph = $opts->{instanciate}) {
         die '['.$self->mongodb_id.'] type is not uri, value: '.$object->{value}
@@ -190,7 +190,7 @@ Example:
 =cut
 
 sub get {
-    my $self = shift;    
+    my $self = shift;
     my ($predicate) = @_;
     my $uri = fencode(resolve($predicate));
     my @values = map {
@@ -204,7 +204,7 @@ sub get {
 =cut
 
 sub add {
-    my $self = shift;    
+    my $self = shift;
     my ($predicate, $value) = @_;
     my $uri = fencode(resolve($predicate));
     my $props = $self->_property($uri);
@@ -218,7 +218,7 @@ sub add {
 =cut
 
 sub del {
-    my $self = shift;    
+    my $self = shift;
     my ($predicate, $value) = @_;
     my $uri = fencode(resolve($predicate));
     my $props = $self->_property($uri);
@@ -237,7 +237,7 @@ or $self->set( $predicate ); to remove all the values.
 =cut
 
 sub set {
-    my $self = shift;    
+    my $self = shift;
     my $predicate = shift;
     my $values = \@_;
     my $uri = fencode(resolve($predicate));
@@ -284,11 +284,11 @@ Returns a RDF/JSON document. See <http://n2.talis.com/wiki/RDF_JSON_Specificatio
 =cut
 
 sub as_rdf_json {
-    my $self = shift;    
+    my $self = shift;
     my $obj = {
         $self->subject => $self->properties
     };
-    my $j = JSON::Any->new; 
+    my $j = JSON::Any->new;
     return $j->objToJson($obj);
 }
 
@@ -297,8 +297,8 @@ sub as_rdf_json {
 =cut
 
 sub as_rdf_xml {
-    my $self = shift;    
-    # TODO 
+    my $self = shift;
+    # TODO
 }
 
 =head2 $self->as_ntriples
@@ -351,7 +351,7 @@ MongoDB::RDF::Resource can be subsclassed like this:
  $graph->save($r);
 
  ...
- 
+
  my $r = $graph->load('http://myinstance');
  # $r is a MyClass
 
diff --git a/lib/MongoDB/RDF/Serializer.pm b/lib/MongoDB/RDF/Serializer.pm
index e933e19..d7995e2 100644
--- a/lib/MongoDB/RDF/Serializer.pm
+++ b/lib/MongoDB/RDF/Serializer.pm
@@ -4,7 +4,7 @@ use warnings;
 
 =head2 $class->dump( resource => ... )
 
-or 
+or
 
  $class->dump( graph => ... )
  $class->dump( graph => ..., filename => ... )
@@ -38,7 +38,7 @@ sub dump {
 
     }
     else {
-        die "graph or resource required";    
+        die "graph or resource required";
     }
 
     $fh->close if $fh;
@@ -66,8 +66,8 @@ sub serialize_resource { die 'to be overwritten' }
 
 =head2 $class->load( graph => ..., filename => ... )
 
-or 
- $class->load( graph => ... ); # read STDIN 
+or
+ $class->load( graph => ... ); # read STDIN
 
 =cut
 
diff --git a/lib/MongoDB/RDF/Serializer/NTriples.pm b/lib/MongoDB/RDF/Serializer/NTriples.pm
index a1ebb3d..b548f48 100644
--- a/lib/MongoDB/RDF/Serializer/NTriples.pm
+++ b/lib/MongoDB/RDF/Serializer/NTriples.pm
@@ -8,7 +8,7 @@ use Encode;
 
 =head1 DESCRIPTION
 
-NTriples serialization 
+NTriples serialization
 
 =cut
 
@@ -32,7 +32,7 @@ sub _encode_literal {
     $l =~ s/\r/\\r/g;
     $l =~ s/\t/\\t/g;
     $l =~ s/\"/\\"/g;
-    return $l; 
+    return $l;
 }
 
 =head2 serialize_resource
@@ -60,7 +60,7 @@ sub _save_triplet {
     my ($graph, $s, $p, $o) = @_;
     my $resource = $graph->load($s) || MongoDB::RDF::Resource->new($s);
     $resource->add($p => $o);
-    $graph->save($resource); 
+    $graph->save($resource);
 }
 
 sub _clean_line {
@@ -72,7 +72,7 @@ sub _clean_line {
     $line = Encode::decode_utf8($line);
     $line =~ s/^\s+//;
     $line =~ s/\s+$//;
-    return $line; 
+    return $line;
 }
 
 sub _decode_literal {
diff --git a/lib/MongoDB/RDF/Util.pm b/lib/MongoDB/RDF/Util.pm
index 38aa464..7e48843 100644
--- a/lib/MongoDB/RDF/Util.pm
+++ b/lib/MongoDB/RDF/Util.pm
@@ -33,8 +33,8 @@ sub looks_like_uri {  # XXX we may want to not guess, and assume that the value
 
 =head2 fencode
 
-MongoDB doesn't allow '.' in the field names. 
-As the fields names here are URIs, we just encode the '.' to '%2E' 
+MongoDB doesn't allow '.' in the field names.
+As the fields names here are URIs, we just encode the '.' to '%2E'
 
 =cut
 
@@ -66,7 +66,7 @@ sub convert_query {
     $convert_q = sub {
         my ($query) = @_;
         for my $key (keys %$query) {
-            # make this recursive in this case 
+            # make this recursive in this case
             if ($key eq '$or') {
                 $convert_q->($_) for @{ $query->{$key} };
             }
diff --git a/t/02-resource-query.t b/t/02-resource-query.t
index ac6d1f5..f185ad6 100644
--- a/t/02-resource-query.t
+++ b/t/02-resource-query.t
@@ -45,11 +45,11 @@ isa_ok($graph, 'MongoDB::RDF::Graph');
     my $cursor2 = $graph->find({ dc_title => 'my title' });
     isa_ok($cursor2, 'MongoDB::RDF::Cursor');
     cmp_ok($cursor2->count, '==', 1, 'one result');
-    
+
     # check that no index is used
     $cursor = $graph->find({ dc_title => 'my title' });
     ok $cursor->explain->{cursor} =~ /BasicCursor/, 'no index used';
-    
+
     # add an index on dc_title
     $graph->ensure_index({ dc_title => 1}, { name => 'test_index', safe => 1 });
     $cursor = $graph->find({ dc_title => 'my title' });
@@ -90,7 +90,7 @@ isa_ok($graph, 'MongoDB::RDF::Graph');
     $cursor->reset;
     @subset = $cursor->limit(2)->skip(3)->all;
     cmp_ok(scalar(@subset), '==', 2, '2 results');
-    
+
     # or
     my $query = { '$or' => [
         { dc_description => 1 },
diff --git a/t/06-util.t b/t/06-util.t
index a893ebb..78943b1 100644
--- a/t/06-util.t
+++ b/t/06-util.t
@@ -43,6 +43,6 @@ my %canonicals = (
 
 for (keys %canonicals) {
     my $expected = $canonicals{$_};
-    cmp_ok( canonical_uri($_), 'eq', $expected);    
+    cmp_ok( canonical_uri($_), 'eq', $expected);
 }