diff --git includes/theme.inc includes/theme.inc
index 21175e3..869f0c1 100644
--- includes/theme.inc
+++ includes/theme.inc
@@ -2003,7 +2003,10 @@ function template_preprocess_username(&$variables) {
     $variables['link_path'] = 'user/' . $variables['uid'];
   }
   elseif (!empty($account->homepage)) {
-    $variables['link_attributes'] = array('rel' => 'nofollow');
+    // Like the 'class' attribute, the 'rel' attribute can hold a
+    // space-separated set of values, so initialize it as an array to make it
+    // easier for other preprocess functions to append to it.
+    $variables['link_attributes'] = array('rel' => array('nofollow'));
     $variables['link_path'] = $account->homepage;
     $variables['homepage'] = $account->homepage;
   }
@@ -2023,7 +2026,14 @@ function template_process_username(&$variables) {
   // This is done in the process phase so that attributes may be added by
   // modules or the theme during the preprocess phase.
   if (isset($variables['link_path'])) {
-    $variables['link_options']['attributes'] = $variables['link_attributes'] + $variables['attributes_array'];
+    // $variables['attributes_array'] contains attributes that should be applied
+    // whether a link is being rendered or not. $variables['link_attributes']
+    // contains attributes that should only be applied if a link is being
+    // rendered. Preprocess functions are encouraged to use the former unless
+    // they are adding attributes that would be senseless to place on a
+    // non-link. If a link will be rendered, these need to be merged. Some
+    // attributes are themselves arrays, so the merging needs to be recursive.
+    $variables['link_options']['attributes'] = array_merge_recursive($variables['link_attributes'], $variables['attributes_array']);
   }
 }
 
diff --git modules/comment/comment.test modules/comment/comment.test
index 4d41c45..250c461 100644
--- modules/comment/comment.test
+++ modules/comment/comment.test
@@ -149,7 +149,7 @@ class CommentHelperCase extends DrupalWebTestCase {
   }
 
   /**
-   * Set comment form setting.
+   * Set comment form location setting.
    *
    * @param boolean $enabled
    *   Form value.
@@ -881,36 +881,101 @@ class CommentRdfaTestCase extends CommentHelperCase {
     parent::setUp('comment', 'rdf');
 
     $this->admin_user = $this->drupalCreateUser(array('administer content types', 'administer comments', 'administer permissions', 'administer blocks'));
-    $this->web_user = $this->drupalCreateUser(array('access comments', 'post comments', 'create article content'));
-
-    $this->drupalLogin($this->web_user);
-    $this->node = $this->drupalCreateNode(array('type' => 'article', 'promote' => 1));
-    $this->drupalLogout();
-  }
+    $this->web_user = $this->drupalCreateUser(array('access comments', 'post comments', 'create article content', 'access user profiles'));
 
-  function testAttributesInMarkup() {
-    // Set comments to not have subject.
-    $this->drupalLogin($this->admin_user);
-    $this->setCommentPreview(FALSE);
+    // Enabled anonymous user comments.
+    user_role_change_permissions(DRUPAL_ANONYMOUS_RID, array(
+      'access comments' => TRUE,
+      'post comments' => TRUE,
+      'post comments without approval' => TRUE,
+    ));
+    // Allow anonymous to leave their contact information.
+    $this->setCommentAnonymous('1');
+    $this->setCommentPreview(DRUPAL_OPTIONAL);
     $this->setCommentForm(TRUE);
     $this->setCommentSubject(TRUE);
     $this->setCommentSettings('comment_default_mode', COMMENT_MODE_THREADED, t('Comment paging changed.'));
+
+    // Create the nodes on which the test comments will be posted.
+    $this->drupalLogin($this->web_user);
+    $this->node1 = $this->drupalCreateNode(array('type' => 'article', 'promote' => 1));
+    $this->node2 = $this->drupalCreateNode(array('type' => 'article', 'promote' => 1));
     $this->drupalLogout();
+  }
+
+  /**
+   * Tests the presence of the RDFa markup for the title, date and author and
+   * homepage on registered users and anonymous comments.
+   */
+  function testAttributesInRdfaMarkup() {
 
-    // Post comment.
+    // Posts comment #1 as a registered user.
     $this->drupalLogin($this->web_user);
-    $subject_text = 'foo';
-    $comment_text = 'bar';
-    $comment = $this->postComment($this->node, $comment_text, $subject_text, FALSE);
-    $this->drupalGet('node/' . $this->node->nid);
+    $comment1_subject = $this->randomName();
+    $comment1_body = $this->randomName();
+    $comment1 = $this->postComment($this->node1, $comment1_body, $comment1_subject);
+
+    // Tests comment #1 with access to the user profile.
+    $this->drupalGet('node/' . $this->node1->nid);
+    $this->_testBasicCommentRdfaMarkup($comment1);
+
+    // Tests comment #1 with no access to the user profile (as anonymous user).
+    $this->drupalLogout();
+    $this->drupalGet('node/' . $this->node1->nid);
+    $this->_testBasicCommentRdfaMarkup($comment1);
+
+
+    // Posts comment #2 as anonymous user.
+    $comment2_subject = $this->randomName();
+    $comment2_body = $this->randomName();
+    $anonymous_user = array();
+    $anonymous_user['name'] = $this->randomName();
+    $anonymous_user['mail'] = 'tester@simpletest.org';
+    $anonymous_user['homepage'] = 'http://example.org/';
+    $comment2 = $this->postComment($this->node2, $comment2_body, $comment2_subject, $anonymous_user);
+    $this->drupalGet('node/' . $this->node2->nid);
+
+    // Tests comment #2 as anonymous user.
+    $this->_testBasicCommentRdfaMarkup($comment2, $anonymous_user);
+    // Tests the RDFa markup for the homepage (specific to anonymous comments).
+    $comment_homepage = $this->xpath("//div[@typeof='sioct:Post']//span[@rel='sioc:has_creator']/a[contains(@class, 'username') and @typeof='sioc:User' and @property='foaf:name' and @href='http://example.org/' and contains(@rel, 'foaf:page')]");
+    $this->assertTrue(!empty($comment_homepage), t('RDFa markup for the homepage of anonymous user found.'));
+    // There should be no about attribute on anonymous comments.
+    $comment_homepage = $this->xpath("//div[@typeof='sioct:Post']//span[@rel='sioc:has_creator']/a[@about]");
+    $this->assertTrue(empty($comment_homepage), t('No about attribute is present on anonymous user comment.'));
+
+    // Tests comment #2 as logged in user.
+    $this->drupalLogin($this->web_user);
+    $this->drupalGet('node/' . $this->node2->nid);
+    $this->_testBasicCommentRdfaMarkup($comment2, $anonymous_user);
+    // Tests the RDFa markup for the homepage (specific to anonymous comments).
+    $comment_homepage = $this->xpath("//div[@typeof='sioct:Post']//span[@rel='sioc:has_creator']/a[contains(@class, 'username') and @typeof='sioc:User' and @property='foaf:name' and @href='http://example.org/' and contains(@rel, 'foaf:page')]");
+    $this->assertTrue(!empty($comment_homepage), t('RDFa markup for the homepage of anonymous user found.'));
+    // There should be no about attribute on anonymous comments.
+    $comment_homepage = $this->xpath("//div[@typeof='sioct:Post']//span[@rel='sioc:has_creator']/a[@about]");
+    $this->assertTrue(empty($comment_homepage), t('No about attribute is present on anonymous user comment.'));
+  }
 
+  /**
+   * Helper function for testAttributesInRdfaMarkup().
+   *
+   * Tests the current page for basic comment RDFa markup.
+   *
+   * @param $comment
+   *   Comment object.
+   * @param $acount
+   *   An array containing information about an anonymous user.
+   */
+  function _testBasicCommentRdfaMarkup($comment, $account = array()) {
     $comment_container = $this->xpath("//div[contains(@class, 'comment') and @typeof='sioct:Post']");
-    $this->assertFalse(empty($comment_container));
-    $comment_title = $this->xpath("//h3[@property='dc:title']");
-    $this->assertEqual((string)$comment_title[0]->a, 'foo');
+    $this->assertTrue(!empty($comment_container));
+    $comment_title = $this->xpath("//div[@typeof='sioct:Post']//h3[@property='dc:title']");
+    $this->assertEqual((string)$comment_title[0]->a, $comment->subject);
     $comment_date = $this->xpath("//div[@typeof='sioct:Post']//*[contains(@property, 'dc:date') and contains(@property, 'dc:created')]");
-    $this->assertFalse(empty($comment_date));
-    $comment_author = $this->xpath("//div[@typeof='sioct:Post']//*[contains(@property, 'foaf:name')]");
-    $this->assertEqual((string)$comment_author[0], $this->web_user->name);
-  }
+    $this->assertTrue(!empty($comment_date));
+    // The author tag can be either a or span
+    $comment_author = $this->xpath("//div[@typeof='sioct:Post']//span[@rel='sioc:has_creator']/*[contains(@class, 'username') and @typeof='sioc:User' and @property='foaf:name']");
+    $name = empty($account['name']) ? $this->web_user->name : $account['name'] . ' (not verified)';
+    $this->assertEqual((string)$comment_author[0], $name);
+    }
 }
diff --git modules/rdf/rdf.module modules/rdf/rdf.module
index 28035da..14ed0e0 100644
--- modules/rdf/rdf.module
+++ modules/rdf/rdf.module
@@ -402,6 +402,10 @@ function rdf_preprocess_node(&$variables) {
     $date_attributes_array = rdf_rdfa_attributes($variables['rdf_mapping']['created'], $variables['created']);
     $variables['rdf_template_variable_attributes_array']['date'] = $date_attributes_array;
   }
+  // Adds RDFa markup for the relation between the node and its author.
+  if (!empty($variables['rdf_mapping']['uid'])) {
+    $variables['rdf_template_variable_attributes_array']['name']['rel'] = $variables['rdf_mapping']['uid']['predicates'];
+  }
 }
 
 /**
@@ -440,48 +444,46 @@ function rdf_preprocess_user_profile(&$variables) {
  * Implements MODULE_preprocess_HOOK().
  */
 function rdf_preprocess_username(&$variables) {
-  $account = $variables['account'];
-  if (!empty($account->rdf_mapping['name'])) {
-    if ($account->uid != 0) {
-      // The following RDFa construct allows to fit all the needed information
-      // into the a tag and avoids having to wrap it with an extra span.
-
-      // An RDF resource for the user is created with the 'about' attribute and
-      // the profile URI is used to identify this resource. Even if the user
-      // profile is not accessible, we generate its URI regardless in order to
-      // be able to identify the user in RDF.
+  // $variables['account'] is a pseudo account object, and as such, does not
+  // contain the rdf mappings for the user; in the case of nodes and comments,
+  // it contains the mappings for the node or comment object instead. Therefore,
+  // the real account object for the user is needed. The real account object is
+  // needed for this function only; it should not replace $variables['account'].
+  if ($account = user_load($variables['uid'])) {
+    // An RDF resource for the user is created with the 'about' attribute and
+    // the profile URI is used to identify this resource. Even if the user
+    // profile is not accessible, we generate its URI regardless in order to
+    // be able to identify the user in RDF. We do not use this attribute for
+    // the anonymous user because we do not have a user profile URI for it (only
+    // a homepage which cannot be used as user profile in RDF).
+    if ($account->uid > 0) {
       $variables['attributes_array']['about'] = url('user/' . $account->uid);
-      // The 'typeof' attribute specifies the RDF type(s) of this resource. They
-      // are defined in the 'rdftype' property of the user object RDF mapping.
-      // Since the full user object is not available in $variables, it needs to
-      // be loaded. This is due to the collision between the node and user
-      // when they are merged into $account and some properties are overridden.
-      $variables['attributes_array']['typeof'] = user_load($account->uid)->rdf_mapping['rdftype'];
-
-      // The first thing we are describing is the relation between the user and
-      // the parent resource (e.g. a node). Because the set of predicate link
-      // the parent to the user, we must use the 'rev' RDFa attribute to specify
-      // that the relationship is reverse.
-      if (!empty($account->rdf_mapping['uid']['predicates'])) {
-        $variables['attributes_array']['rev'] = $account->rdf_mapping['uid']['predicates'];
-        // We indicate the parent identifier in the 'resource' attribute,
-        // typically this is the entity URI. This is the object in RDF.
-        $parent_uri = '';
-        if (!empty($account->path['source'])) {
-          $parent_uri = url($account->path['source']);
-        }
-        elseif (!empty($account->cid)) {
-          $parent_uri = url('comment/' . $account->cid, array('fragment' => 'comment-' . $account->cid));
-        }
-        $variables['attributes_array']['resource'] = $parent_uri;
-      }
+    }
+
+    // The remaining attributes are defined by RDFa as lists
+    // (http://www.w3.org/TR/rdfa-syntax/#rdfa-attributes). Therefore, merge
+    // rather than override, so as not to clobber values set by earlier
+    // preprocess functions.
+    $attributes = array();
 
-      // The second information we annotate is the name of the user with the
-      // 'property' attribute. We do not need to specify the RDF object here
-      // because it's the value inside the a tag which will be used
-      // automatically according to the RDFa parsing rules.
-      $variables['attributes_array']['property'] = $account->rdf_mapping['name']['predicates'];
+    // The 'typeof' attribute specifies the RDF type(s) of this resource. They
+    // are defined in the 'rdftype' property of the user object RDF mapping.
+    if (!empty($account->rdf_mapping['rdftype'])) {
+      $attributes['typeof'] = $account->rdf_mapping['rdftype'];
     }
+
+    // Annotate the user name in RDFa. The attribute 'property' is used here
+    // because the user name is a literal.
+    if (!empty($account->rdf_mapping['name'])) {
+      $attributes['property'] = $account->rdf_mapping['name']['predicates'];
+    }
+
+    // Add the homepage RDFa markup if present.
+    if (!empty($variables['homepage']) && !empty($account->rdf_mapping['homepage'])) {
+      $attributes['rel'] = $account->rdf_mapping['homepage']['predicates'];
+    }
+
+    $variables['attributes_array'] = array_merge_recursive($variables['attributes_array'], $attributes);
   }
 }
 
@@ -503,6 +505,10 @@ function rdf_preprocess_comment(&$variables) {
     $date_attributes_array = rdf_rdfa_attributes($comment->rdf_mapping['created'], $comment->created);
     $variables['rdf_template_variable_attributes_array']['created'] = $date_attributes_array;
   }
+  // Adds RDFa markup for the relation between the comment and its author.
+  if (!empty($comment->rdf_mapping['uid'])) {
+    $variables['rdf_template_variable_attributes_array']['author']['rel'] = $comment->rdf_mapping['uid']['predicates'];
+  }
   if (!empty($comment->rdf_mapping['title'])) {
     // Adds RDFa markup to the subject of the comment. Because the RDFa markup is
     // added to an h3 tag which might contain HTML code, we specify an empty
diff --git modules/user/user.module modules/user/user.module
index b747813..eaa524d 100644
--- modules/user/user.module
+++ modules/user/user.module
@@ -3275,6 +3275,10 @@ function user_rdf_mapping() {
         'name' => array(
           'predicates' => array('foaf:name'),
         ),
+        'homepage' => array(
+          'predicates' => array('foaf:page'),
+          'type' => 'rel',
+        ),
       ),
     ),
   );