diff --git a/src/classes/ExtendedGraph.class.php b/src/classes/ExtendedGraph.class.php
index f7579ff9..80aaa835 100644
--- a/src/classes/ExtendedGraph.class.php
+++ b/src/classes/ExtendedGraph.class.php
@@ -141,7 +141,10 @@ public function make_resource_array($resource) {
      * @return boolean true if the triple was new, false if it already existed in the graph
      */
     public function add_resource_triple($s, $p, $o) {
-        return $this->_add_triple($s, $p, array('type' => strpos($o, '_:' ) === 0 ? 'bnode' : 'uri', 'value' => $o));
+        if($this->isValidResource($o)) {
+            return $this->_add_triple($s, $p, array('type' => strpos($o, '_:') === 0 ? 'bnode' : 'uri', 'value' => $o));
+        }
+        return false;
     }
 
     /**
@@ -154,34 +157,45 @@ public function add_resource_triple($s, $p, $o) {
      * @return boolean true if the triple was new, false if it already existed in the graph
      */
     public function add_literal_triple($s, $p, $o, $lang = null, $dt = null) {
-        $o_info = array('type' => 'literal', 'value' => $o);
-        if ( $lang != null ) {
-            $o_info['lang'] = $lang;
-        }
-        if ( $dt != null ) {
-            $o_info['datatype'] = $dt;
+        if($this->isValidLiteral($o)) {
+            $o_info = array('type' => 'literal', 'value' => $o);
+            if ($lang != null) {
+                $o_info['lang'] = $lang;
+            }
+            if ($dt != null) {
+                $o_info['datatype'] = $dt;
+            }
+            return $this->_add_triple($s, $p, $o_info);
         }
-        return $this->_add_triple($s, $p, $o_info);
+        return false;
     }
 
     /**
      * @param string $s
      * @param string $p
      * @param array $o_info
+     * @throws Exceptions\Exception
      * @return bool
      */
     private function _add_triple($s, $p, Array $o_info) {
+        // The value $o should already have been validated by this point
+        // It's validation differs depending on whether it is a literal or resource
+        // So just check the subject and predicate here...
+        if(!$this->isValidResource($s)){
+            throw new \Tripod\Exceptions\Exception("The subject is invalid");
+        }
+        if(!$this->isValidResource($p)){
+            throw new \Tripod\Exceptions\Exception("The predicate is invalid");
+        }
         if (!isset($this->_index[$s])) {
             $this->_index[$s] = array();
-            $this->_index[$s][$p] = array( $o_info );
+            $this->_index[$s][$p] = array($o_info);
             return true;
-        }
-        elseif (!isset($this->_index[$s][$p])) {
-            $this->_index[$s][$p] = array( $o_info);
+        } elseif (!isset($this->_index[$s][$p])) {
+            $this->_index[$s][$p] = array($o_info);
             return true;
-        }
-        else {
-            if ( ! in_array( $o_info, $this->_index[$s][$p] ) ) {
+        } else {
+            if (!in_array($o_info, $this->_index[$s][$p])) {
                 $this->_index[$s][$p][] = $o_info;
                 return true;
             }
@@ -189,6 +203,37 @@ private function _add_triple($s, $p, Array $o_info) {
         return false;
     }
 
+
+    /**
+     * Check if a triple value is valid.
+     *
+     * Ideally a valid literal value should be a string
+     * but accepting scalars so we can handle legacy data
+     * which was not type-checked.
+     *
+     * @param string $value
+     * @return bool
+     */
+    protected function isValidLiteral($value){
+        if(!is_scalar($value)){
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Check if a triple value is valid.
+     *
+     * @param string $value
+     * @return bool
+     */
+    protected function isValidResource($value){
+        if(!is_string($value) || empty($value)){
+            return false;
+        }
+        return true;
+    }
+
     /**
      * @deprecated this is deprecated
      */
diff --git a/src/mongo/MongoGraph.class.php b/src/mongo/MongoGraph.class.php
index 554db802..436131c9 100644
--- a/src/mongo/MongoGraph.class.php
+++ b/src/mongo/MongoGraph.class.php
@@ -119,6 +119,7 @@ function to_tripod_view_array($docId,$context)
 
     /**
      * @param array $tarray
+     * @throws \Tripod\Exceptions\Exception
      */
     private function add_tarray_to_index($tarray)
     {
@@ -129,7 +130,17 @@ private function add_tarray_to_index($tarray)
             if($key[0] != '_')
             {
                 $predicate = $this->qname_to_uri($key);
-                $predObjects[$predicate] = $this->toGraphValueObject($value);
+                $graphValueObject = $this->toGraphValueObject($value);
+                // Only add if valid values have been found
+                if (!empty($graphValueObject)) {
+                    $predObjects[$predicate] = $graphValueObject;
+                }
+            }
+            else if($key == "_id"){
+                // If the subject is invalid then throw an exception
+                if(!isset($value['r']) || !$this->isValidResource($value['r'])){
+                    throw new \Tripod\Exceptions\Exception("The subject cannot be an empty string");
+                }
             }
         }
         $_i[$this->_labeller->qname_to_alias($tarray["_id"][_ID_RESOURCE])] = $predObjects;
@@ -138,39 +149,61 @@ private function add_tarray_to_index($tarray)
 
     /**
      * Convert from Tripod value object format (comapct) to ExtendedGraph format (verbose)
+     *
      * @param array $mongoValueObject
      * @return array
      */
     private function toGraphValueObject($mongoValueObject)
     {
-        $simpleGraphValueObject = null;
+        $simpleGraphValueObject = array();
 
         if (array_key_exists(VALUE_LITERAL,$mongoValueObject))
         {
-            // single value literal
-            $simpleGraphValueObject[] = array(
-                'type'=>'literal',
-                'value'=>$mongoValueObject[VALUE_LITERAL]);
+            // only allow valid values
+            if($this->isValidLiteral($mongoValueObject[VALUE_LITERAL])){
+                // single value literal
+                $simpleGraphValueObject[] = array(
+                    'type'=>'literal',
+                    'value'=>$mongoValueObject[VALUE_LITERAL]);
+            }
         }
         else if (array_key_exists(VALUE_URI,$mongoValueObject))
         {
-            // single value literal
-            $simpleGraphValueObject[] = array(
-                'type'=>'uri',
-                'value'=>$this->_labeller->qname_to_alias($mongoValueObject[VALUE_URI]));
+            // only allow valid values
+            if($this->isValidResource($mongoValueObject[VALUE_URI])) {
+                // single value uri
+                $simpleGraphValueObject[] = array(
+                    'type' => 'uri',
+                    'value' => $this->_labeller->qname_to_alias($mongoValueObject[VALUE_URI]));
+            }
         }
         else
         {
+            // If we have an array of values
             foreach ($mongoValueObject as $kvp)
             {
                 foreach ($kvp as $type=>$value)
                 {
+                    // Make sure the value is valid
+                    if($type==VALUE_LITERAL){
+                        if(!$this->isValidLiteral($value)){
+                            continue;
+                        }
+                        $valueTypeLabel = 'literal';
+                    }
+                    else{
+                        if(!$this->isValidResource($value)){
+                            continue;
+                        }
+                        $valueTypeLabel = 'uri';
+                    }
                     $simpleGraphValueObject[] = array(
-                        'type'=>($type==VALUE_LITERAL) ? 'literal' : 'uri',
+                        'type'=>$valueTypeLabel,
                         'value'=>($type==VALUE_URI) ? $this->_labeller->qname_to_alias($value) : $value);
                 }
             }
         }
+        // Otherwise we have found valid values
         return $simpleGraphValueObject;
     }
 
diff --git a/test/unit/ExtendedGraphTest.php b/test/unit/ExtendedGraphTest.php
index 37347d4e..f85986ed 100644
--- a/test/unit/ExtendedGraphTest.php
+++ b/test/unit/ExtendedGraphTest.php
@@ -23,6 +23,176 @@ protected function setUp()
         echo "\nTest: {$className}->{$testName}\n";
     }
 
+    /**
+     * @dataProvider addValidValueToLiteralResultsInTriple_Provider
+     */
+    public function testAddValidValueToLiteralResultsInTriple($value)
+    {
+        $graph = new ExtendedGraph();
+        $addResult = $graph->add_literal_triple('http://some/subject/1', 'http://some/predicate', $value);
+        $this->assertTrue($addResult, 'The triple should have been added for this value');
+
+        $hasPropertyResult = $graph->subject_has_property('http://some/subject/1', 'http://some/predicate');
+        $this->assertTrue($hasPropertyResult, 'The triple should have been added for this value');
+    }
+    public function addValidValueToLiteralResultsInTriple_Provider(){
+        return array(
+            array('String'),
+            array(1),
+            array(1.2),
+            array(true)
+        );
+    }
+
+    /**
+     * @dataProvider addInvalidValueToLiteralResultsInNoTriple_Provider
+     */
+    public function testAddInvalidValueToLiteralResultsInNoTriple($value)
+    {
+        $graph = new ExtendedGraph();
+        $addResult = $graph->add_literal_triple('http://some/subject/1', 'http://some/predicate', $value);
+        $this->assertFalse($addResult, 'The triple should not have been added for this value');
+
+        $hasPropertyResult = $graph->subject_has_property('http://some/subject/1', 'http://some/predicate');
+        $this->assertFalse($hasPropertyResult, 'The triple should not have been added for this value');
+    }
+    public function addInvalidValueToLiteralResultsInNoTriple_Provider(){
+        return array(
+            array(null),
+            array(new stdClass()),
+            array(function(){})
+        );
+    }
+
+    /**
+     * @dataProvider addInvalidSubjectToLiteralResultsInNoTriple_Provider
+     */
+    public function testAddInvalidSubjectToLiteralThrowsException($value)
+    {
+        $this->setExpectedException('\Tripod\Exceptions\Exception');
+
+        $graph = new ExtendedGraph();
+        $graph->add_resource_triple($value, 'http://some/predicate', 'http://someplace.com');
+    }
+    public function addInvalidSubjectToLiteralResultsInNoTriple_Provider(){
+        return array(
+            array(""),
+            array(1),
+            array(1.2),
+            array(true),
+            array(array()),
+            array(null),
+            array(new stdClass()),
+            array(function(){})
+        );
+    }
+
+    /**
+     * @dataProvider addInvalidSubjectToLiteralResultsInNoTriple_Provider
+     */
+    public function testAddInvalidPredicateToLiteralThrowsException($value)
+    {
+        $this->setExpectedException('\Tripod\Exceptions\Exception');
+
+        $graph = new ExtendedGraph();
+        $graph->add_resource_triple('http://some/subject/1', $value, 'http://someplace.com');
+    }
+    public function addInvalidPredicateToLiteralResultsInNoTriple_Provider(){
+        return array(
+            array(""),
+            array(1),
+            array(1.2),
+            array(true),
+            array(array()),
+            array(null),
+            array(new stdClass()),
+            array(function(){})
+        );
+    }
+
+    public function testAddValidValueToResourceResultsInTriple()
+    {
+        $value = 'A String';
+        $graph = new ExtendedGraph();
+        $addResult = $graph->add_resource_triple('http://some/subject/1', 'http://some/predicate', $value);
+        $this->assertTrue($addResult, 'The triple should have been added for this value');
+
+        $hasPropertyResult = $graph->subject_has_property('http://some/subject/1', 'http://some/predicate');
+        $this->assertTrue($hasPropertyResult, 'The triple should have been added for this value');
+    }
+
+
+    /**
+     * @dataProvider addInvalidValueToResourceResultsInNoTriple_Provider
+     */
+    public function testAddInvalidValueToResourceResultsInNoTriple($value)
+    {
+        $graph = new ExtendedGraph();
+
+        $addResult = $graph->add_resource_triple('http://some/subject/1', 'http://some/predicate', $value);
+        $this->assertFalse($addResult, 'The triple should not have been added for this value');
+
+        $hasPropertyResult = $graph->subject_has_property('http://some/subject/1', 'http://some/predicate');
+        $this->assertFalse($hasPropertyResult, 'The triple should not have been added for this value');
+    }
+    public function addInvalidValueToResourceResultsInNoTriple_Provider(){
+        return array(
+            array(1),
+            array(1.2),
+            array(true),
+            array(array()),
+            array(null),
+            array(new stdClass()),
+            array(function(){})
+        );
+    }
+
+    /**
+     * @dataProvider addInvalidSubjectToResourceResultsInNoTriple_Provider
+     */
+    public function testAddInvalidSubjectToResourceThrowsException($value)
+    {
+        $this->setExpectedException('\Tripod\Exceptions\Exception');
+
+        $graph = new ExtendedGraph();
+        $graph->add_resource_triple($value, 'http://some/predicate', 'http://someplace.com');
+    }
+    public function addInvalidSubjectToResourceResultsInNoTriple_Provider(){
+        return array(
+            array(""),
+            array(1),
+            array(1.2),
+            array(true),
+            array(array()),
+            array(null),
+            array(new stdClass()),
+            array(function(){})
+        );
+    }
+
+    /**
+     * @dataProvider addInvalidSubjectToLiteralResultsInNoTriple_Provider
+     */
+    public function testAddInvalidPredicateToResourceThrowsException($value)
+    {
+        $this->setExpectedException('\Tripod\Exceptions\Exception');
+
+        $graph = new ExtendedGraph();
+        $graph->add_resource_triple('http://some/subject/1', $value, 'http://someplace.com');
+    }
+    public function addInvalidPredicateToResourceResultsInNoTriple_Provider(){
+        return array(
+            array(""),
+            array(1),
+            array(1.2),
+            array(true),
+            array(array()),
+            array(null),
+            array(new stdClass()),
+            array(function(){})
+        );
+    }
+
     public function testRemoveProperties()
     {
         $graph = new ExtendedGraph();
diff --git a/test/unit/mongo/MongoGraphTest.php b/test/unit/mongo/MongoGraphTest.php
index eba3556c..98243b98 100644
--- a/test/unit/mongo/MongoGraphTest.php
+++ b/test/unit/mongo/MongoGraphTest.php
@@ -102,6 +102,223 @@ public function testAddTripodArraySingleDoc()
         $this->assertEquals($expected, $g);
     }
 
+    /**
+     * @dataProvider addTripodArrayContainingValidLiteralValues_Provider
+     */
+    public function testAddTripodArrayContainingValidLiteralValues($value)
+    {
+        $doc = array(
+            "_id"=>array("r"=>"http://talisaspire.com/works/4d101f63c10a6-2", "c"=>"http://talisaspire.com/works/4d101f63c10a6-2"),
+            "_version"=>0,
+            "rdf:type"=>array(
+                array("l"=>$value),
+                array("l"=>"a Value"),
+            ),
+            "bibo:isbn13"=>array("l"=>"9211234567890"),
+            "bibo:isbn10"=>array("l"=>$value)
+        );
+
+        $expected = new \Tripod\Mongo\MongoGraph();
+        $expected->add_literal_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("bibo:isbn13"),"9211234567890");
+        $expected->add_literal_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("bibo:isbn10"),$value);
+        $expected->add_literal_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("rdf:type"),$value);
+        $expected->add_literal_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("rdf:type"),"a Value");
+
+        $g = new \Tripod\Mongo\MongoGraph();
+        $g->add_tripod_array($doc);
+
+        $this->assertEquals($expected, $g);
+    }
+    public function addTripodArrayContainingValidLiteralValues_Provider(){
+        return array(
+            array('A String'),
+            array(1),
+            array(1.2),
+            array(true)
+        );
+    }
+
+    /**
+     * @dataProvider addTripodArrayContainingInvalidLiteralValues_Provider
+     */
+    public function testAddTripodArrayContainingInvalidLiteralValues($value)
+    {
+        $doc = array(
+            "_id"=>array("r"=>"http://talisaspire.com/works/4d101f63c10a6-2", "c"=>"http://talisaspire.com/works/4d101f63c10a6-2"),
+            "_version"=>0,
+            "rdf:type"=>array(
+                array("l"=>$value),
+                array("l"=>"a Value"),
+            ),
+            "bibo:isbn13"=>array("l"=>"9211234567890"),
+            "bibo:isbn10"=>array("l"=>$value)
+        );
+
+        $expected = new \Tripod\Mongo\MongoGraph();
+        $expected->add_literal_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("bibo:isbn13"),"9211234567890");
+        $expected->add_literal_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("rdf:type"),"a Value");
+
+        $g = new \Tripod\Mongo\MongoGraph();
+        $g->add_tripod_array($doc);
+
+        $this->assertEquals($expected, $g);
+    }
+    public function addTripodArrayContainingInvalidLiteralValues_Provider(){
+        return array(
+            array(null),
+            array(new stdClass()),
+            array(function(){})
+        );
+    }
+
+    /**
+     * @dataProvider addTripodArrayContainingInvalidPredicates_Provider
+     */
+    public function testAddTripodArrayContainingInvalidPredicates($value)
+    {
+        $this->setExpectedException('\Tripod\Exceptions\LabellerException');
+        $doc = array(
+            "_id"=>array("r"=>"http://talisaspire.com/works/4d101f63c10a6-2", "c"=>"http://talisaspire.com/works/4d101f63c10a6-2"),
+            "_version"=>0,
+            "rdf:type"=>array(
+                array("l"=>"a Value"),
+            ),
+            "bibo:isbn13"=>array("l"=>"9211234567890"),
+            $value=>array("l"=>"9211234567890")
+        );
+
+        $expected = new \Tripod\Mongo\MongoGraph();
+        $expected->add_literal_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("bibo:isbn13"),"9211234567890");
+        $expected->add_literal_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("rdf:type"),"a Value");
+
+        $g = new \Tripod\Mongo\MongoGraph();
+        $g->add_tripod_array($doc);
+    }
+    public function addTripodArrayContainingInvalidPredicates_Provider(){
+        return array(
+            array(1),
+            array(1.2),
+            array(true),
+        );
+    }
+
+    /**
+     *
+     * We are expecting the labeller
+     *
+     */
+    public function testAddTripodArrayContainingEmptyPredicate()
+    {
+        // An Uninitialized string offset should occur if an empty predicate is passed.
+        $this->setExpectedException("PHPUnit_Framework_Error");
+        $doc = array(
+            "_id"=>array("r"=>"http://talisaspire.com/works/4d101f63c10a6-2", "c"=>"http://talisaspire.com/works/4d101f63c10a6-2"),
+            "_version"=>0,
+            "rdf:type"=>array(
+                array("l"=>"a Value"),
+            ),
+            "bibo:isbn13"=>array("l"=>"9211234567890"),
+            ""=>array("l"=>"9211234567890")
+        );
+
+        $expected = new \Tripod\Mongo\MongoGraph();
+        $expected->add_literal_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("bibo:isbn13"),"9211234567890");
+        $expected->add_literal_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("rdf:type"),"a Value");
+
+        $g = new \Tripod\Mongo\MongoGraph();
+        $g->add_tripod_array($doc);
+    }
+
+    /**
+     * @dataProvider addTripodArrayContainingInvalidSubject_Provider
+     */
+    public function testAddTripodArrayContainingInvalidSubject($value)
+    {
+        $this->setExpectedException('\Tripod\Exceptions\Exception');
+        $doc = array(
+            "_id"=>array("r"=>$value, "c"=>"http://talisaspire.com/works/4d101f63c10a6-2"),
+            "_version"=>0,
+            "rdf:type"=>array(
+                array("l"=>"a Value"),
+            ),
+            "bibo:isbn13"=>array("l"=>"9211234567890"),
+        );
+
+        $g = new \Tripod\Mongo\MongoGraph();
+        $g->add_tripod_array($doc);
+    }
+    public function addTripodArrayContainingInvalidSubject_Provider(){
+        return array(
+            array(""),
+            array(1),
+            array(1.2),
+            array(true),
+        );
+    }
+
+    public function testAddTripodArrayContainingValidResourceValues()
+    {
+        $value = 'A String';
+        $doc = array(
+            "_id"=>array("r"=>"http://talisaspire.com/works/4d101f63c10a6-2", "c"=>"http://talisaspire.com/works/4d101f63c10a6-2"),
+            "_version"=>0,
+            "dct:subject"=>array("u"=>"http://talisaspire.com/disciplines/physics"),
+            "dct:publisher"=>array("u"=>$value),
+            "rdf:type"=>array(
+                array("u"=>$value),
+                array("u"=>"http://talisaspire.com/schema#Work")
+            ),
+        );
+
+        $expected = new \Tripod\Mongo\MongoGraph();
+        $expected->add_resource_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("dct:subject"),"http://talisaspire.com/disciplines/physics");
+        $expected->add_resource_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("dct:publisher"),$value);
+        $expected->add_resource_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("rdf:type"),$value);
+        $expected->add_resource_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("rdf:type"),"http://talisaspire.com/schema#Work");
+
+        $g = new \Tripod\Mongo\MongoGraph();
+        $g->add_tripod_array($doc);
+
+        $this->assertEquals($expected, $g);
+    }
+
+    /**
+     * @dataProvider addTripodArrayContainingInvalidResourceValues_Provider
+     */
+    public function testAddTripodArrayContainingInvalidResourceValues($value)
+    {
+        $doc = array(
+            "_id"=>array("r"=>"http://talisaspire.com/works/4d101f63c10a6-2", "c"=>"http://talisaspire.com/works/4d101f63c10a6-2"),
+            "_version"=>0,
+            "dct:subject"=>array("u"=>"http://talisaspire.com/disciplines/physics"),
+            "dct:publisher"=>array("u"=>$value),
+            "rdf:type"=>array(
+                array("u"=>$value),
+                array("u"=>"http://talisaspire.com/schema#Work")
+            ),
+        );
+
+        $expected = new \Tripod\Mongo\MongoGraph();
+        $expected->add_resource_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("dct:subject"),"http://talisaspire.com/disciplines/physics");
+        $expected->add_resource_triple("http://talisaspire.com/works/4d101f63c10a6-2", $expected->qname_to_uri("rdf:type"),"http://talisaspire.com/schema#Work");
+
+        $g = new \Tripod\Mongo\MongoGraph();
+        $g->add_tripod_array($doc);
+
+        $this->assertEquals($expected, $g);
+    }
+    public function addTripodArrayContainingInvalidResourceValues_Provider(){
+        return array(
+            array(1),
+            array(1.2),
+            array(true),
+            array(array()),
+            array(null),
+            array(new stdClass()),
+            array(function(){})
+        );
+    }
+
     public function testAddTripodArrayWhenAddingViews()
     {
         // view contains 4 subgraphs