diff --git a/src/ol/expr/expression.js b/src/ol/expr/expression.js
index 277364d750..bc732e825f 100644
--- a/src/ol/expr/expression.js
+++ b/src/ol/expr/expression.js
@@ -123,7 +123,7 @@ ol.expr.lib[ol.expr.functions.EXTENT] = function(minX, maxX, minY, maxY,
     opt_projection, opt_attribute) {
   var intersects = false;
   var geometry = goog.isDef(opt_attribute) ?
-      this.getAttributes()[opt_attribute] : this.getGeometry();
+      this.get(opt_attribute) : this.getGeometry();
   if (geometry) {
     intersects = ol.extent.intersects(geometry.getBounds(),
         [minX, maxX, minY, maxY]);
@@ -167,7 +167,7 @@ ol.expr.lib[ol.expr.functions.LIKE] = function(attribute, value, wildCard,
     singleChar, escapeChar, matchCase) {
   if (wildCard == '.') {
     throw new Error('"." is an unsupported wildCard character for ' +
-        'ol.filter.Comparison');
+        'the "like" function');
   }
   // set UMN MapServer defaults for unspecified parameters
   wildCard = goog.isDef(wildCard) ? wildCard : '*';
@@ -184,9 +184,8 @@ ol.expr.lib[ol.expr.functions.LIKE] = function(attribute, value, wildCard,
       new RegExp('\\\\.\\*', 'g'), '\\' + wildCard);
   val = value.replace(
       new RegExp('\\\\\\.', 'g'), '\\' + singleChar);
-  var attributes = this.getAttributes();
   var modifiers = (matchCase === false) ? 'gi' : 'g';
-  return new RegExp(val, modifiers).test(attributes[attribute]);
+  return new RegExp(val, modifiers).test(this.get(attribute));
 };
 
 
@@ -197,11 +196,11 @@ ol.expr.lib[ol.expr.functions.LIKE] = function(attribute, value, wildCard,
  * @this {ol.Feature}
  */
 ol.expr.lib[ol.expr.functions.IEQ] = function(attribute, value) {
-  var attributes = this.getAttributes();
-  if (goog.isString(value) && goog.isString(attributes[attribute])) {
-    return value.toUpperCase() == attributes[attribute].toUpperCase();
+  var attributeValue = this.get(attribute);
+  if (goog.isString(value) && goog.isString(attributeValue)) {
+    return value.toUpperCase() == attributeValue.toUpperCase();
   } else {
-    return value == attributes[attribute];
+    return value == attributeValue;
   }
 };
 
@@ -213,11 +212,11 @@ ol.expr.lib[ol.expr.functions.IEQ] = function(attribute, value) {
  * @this {ol.Feature}
  */
 ol.expr.lib[ol.expr.functions.INEQ] = function(attribute, value) {
-  var attributes = this.getAttributes();
-  if (goog.isString(value) && goog.isString(attributes[attribute])) {
-    return value.toUpperCase() == attributes[attribute].toUpperCase();
+  var attributeValue = this.get(attribute);
+  if (goog.isString(value) && goog.isString(attributeValue)) {
+    return value.toUpperCase() == attributeValue.toUpperCase();
   } else {
-    return value != attributes[attribute];
+    return value != attributeValue;
   }
 };
 
diff --git a/src/ol/expr/expressions.js b/src/ol/expr/expressions.js
index bd827885ea..1f16e7ff9c 100644
--- a/src/ol/expr/expressions.js
+++ b/src/ol/expr/expressions.js
@@ -277,12 +277,12 @@ ol.expr.Identifier.prototype.getName = function() {
  *
  * @constructor
  * @extends {ol.expr.Expression}
- * @param {string|number|boolean|null} value A literal value.
+ * @param {string|number|boolean|Date|null} value A literal value.
  */
 ol.expr.Literal = function(value) {
 
   /**
-   * @type {string|number|boolean|null}
+   * @type {string|number|boolean|Date|null}
    * @private
    */
   this.value_ = value;
@@ -301,7 +301,7 @@ ol.expr.Literal.prototype.evaluate = function() {
 
 /**
  * Get the literal value.
- * @return {string|number|boolean|null} The literal value.
+ * @return {string|number|boolean|Date|null} The literal value.
  */
 ol.expr.Literal.prototype.getValue = function() {
   return this.value_;
diff --git a/src/ol/parser/ogc/filter_v1.js b/src/ol/parser/ogc/filter_v1.js
index 4b7f1063ec..3085e1397d 100644
--- a/src/ol/parser/ogc/filter_v1.js
+++ b/src/ol/parser/ogc/filter_v1.js
@@ -1,12 +1,15 @@
 goog.provide('ol.parser.ogc.Filter_v1');
 goog.require('goog.array');
+goog.require('goog.asserts');
 goog.require('goog.dom.xml');
+goog.require('goog.object');
 goog.require('goog.string');
 goog.require('ol.expr');
 goog.require('ol.expr.Call');
 goog.require('ol.expr.Comparison');
 goog.require('ol.expr.ComparisonOp');
 goog.require('ol.expr.Identifier');
+goog.require('ol.expr.Literal');
 goog.require('ol.expr.Logical');
 goog.require('ol.expr.LogicalOp');
 goog.require('ol.expr.Not');
@@ -24,18 +27,18 @@ ol.parser.ogc.Filter_v1 = function() {
   this.errorProperty = 'filter';
   this.readers = {
     'http://www.opengis.net/ogc': {
-      '_expression': function(node) {
-        // only the simplest of ogc:expression handled
-        // "some text and an <PropertyName>attribute</PropertyName>"
+      _expression: function(node) {
         var obj, value = '';
         for (var child = node.firstChild; child; child = child.nextSibling) {
           switch (child.nodeType) {
             case 1:
               obj = this.readNode(child);
               if (obj['property']) {
-                value += obj['property'];
+                value += obj['property'].getName();
               } else if (goog.isDef(obj['value'])) {
-                value += obj['value'];
+                // TODO adding this to value and then parsing causes
+                // ol.expr.UnexpectedToken on e.g. 10
+                return obj['value'];
               }
               break;
             case 3: // text node
@@ -46,17 +49,17 @@ ol.parser.ogc.Filter_v1 = function() {
               break;
           }
         }
-        return value;
+        return ol.expr.parse(value);
       },
       'Filter': function(node, obj) {
         var container = {
           'filters': []
         };
         this.readChildNodes(node, container);
-        if (goog.isDef(container['fids'])) {
+        if (goog.isDef(container.fids)) {
           obj['filter'] = new ol.expr.Call(
               new ol.expr.Identifier(ol.expr.functions.FID),
-              container['fids']);
+              goog.object.getValues(container.fids));
         } else if (container['filters'].length > 0) {
           obj['filter'] = container['filters'][0];
         }
@@ -64,10 +67,12 @@ ol.parser.ogc.Filter_v1 = function() {
       'FeatureId': function(node, obj) {
         var fid = node.getAttribute('fid');
         if (fid) {
-          if (!goog.isDef(obj['fids'])) {
-            obj['fids'] = {};
+          if (!goog.isDef(obj.fids)) {
+            obj.fids = {};
+          }
+          if (!obj.fids.hasOwnProperty(fid)) {
+            obj.fids[fid] = new ol.expr.Literal(fid);
           }
-          obj['fids'][fid] = true;
         }
       },
       'And': function(node, obj) {
@@ -97,7 +102,7 @@ ol.parser.ogc.Filter_v1 = function() {
         obj['filters'].push(new ol.expr.Comparison(
             ol.expr.ComparisonOp.EQ,
             container['property'],
-            null));
+            new ol.expr.Literal(null)));
       },
       'PropertyIsLessThan': function(node, obj) {
         var container = {};
@@ -143,28 +148,29 @@ ol.parser.ogc.Filter_v1 = function() {
       'Literal': function(node, obj) {
         var nodeValue = this.getChildValue(node);
         var value = goog.string.toNumber(nodeValue);
-        obj['value'] = isNaN(value) ? nodeValue : value;
+        obj['value'] = new ol.expr.Literal(isNaN(value) ? nodeValue : value);
       },
       'PropertyName': function(node, obj) {
-        obj['property'] = this.getChildValue(node);
+        obj['property'] = new ol.expr.Identifier(this.getChildValue(node));
       },
       'LowerBoundary': function(node, obj) {
         var readers = this.readers[this.defaultNamespaceURI];
-        obj['lowerBoundary'] = goog.string.toNumber(
-            readers['_expression'].call(this, node));
+        obj['lowerBoundary'] = readers._expression.call(this, node);
       },
       'UpperBoundary': function(node, obj) {
         var readers = this.readers[this.defaultNamespaceURI];
-        obj['upperBoundary'] = goog.string.toNumber(
-            readers['_expression'].call(this, node));
+        obj['upperBoundary'] = readers._expression.call(this, node);
       },
-      '_spatial': function(node, obj, identifier) {
+      _spatial: function(node, obj, identifier) {
         var args = [], container = {};
         this.readChildNodes(node, container);
         if (goog.isDef(container.geometry)) {
-          args.push(this.gml_.createGeometry(container));
+          args.push(new ol.expr.Literal(this.gml_.createGeometry(container)));
         } else {
-          args = container['bounds'];
+          args = [new ol.expr.Literal(container.bounds[0]),
+                new ol.expr.Literal(container.bounds[1]),
+                new ol.expr.Literal(container.bounds[2]),
+                new ol.expr.Literal(container.bounds[3])];
         }
         if (goog.isDef(container['distance'])) {
           args.push(container['distance']);
@@ -172,7 +178,7 @@ ol.parser.ogc.Filter_v1 = function() {
         if (goog.isDef(container['distanceUnits'])) {
           args.push(container['distanceUnits']);
         }
-        args.push(container['projection']);
+        args.push(new ol.expr.Literal(container.projection));
         if (goog.isDef(container['property'])) {
           args.push(container['property']);
         }
@@ -181,32 +187,32 @@ ol.parser.ogc.Filter_v1 = function() {
       },
       'BBOX': function(node, obj) {
         var readers = this.readers[this.defaultNamespaceURI];
-        readers['_spatial'].call(this, node, obj,
+        readers._spatial.call(this, node, obj,
             ol.expr.functions.EXTENT);
       },
       'Intersects': function(node, obj) {
         var readers = this.readers[this.defaultNamespaceURI];
-        readers['_spatial'].call(this, node, obj,
+        readers._spatial.call(this, node, obj,
             ol.expr.functions.INTERSECTS);
       },
       'Within': function(node, obj) {
         var readers = this.readers[this.defaultNamespaceURI];
-        readers['_spatial'].call(this, node, obj,
+        readers._spatial.call(this, node, obj,
             ol.expr.functions.WITHIN);
       },
       'Contains': function(node, obj) {
         var readers = this.readers[this.defaultNamespaceURI];
-        readers['_spatial'].call(this, node, obj,
+        readers._spatial.call(this, node, obj,
             ol.expr.functions.CONTAINS);
       },
       'DWithin': function(node, obj) {
         var readers = this.readers[this.defaultNamespaceURI];
-        readers['_spatial'].call(this, node, obj,
+        readers._spatial.call(this, node, obj,
             ol.expr.functions.DWITHIN);
       },
       'Distance': function(node, obj) {
-        obj['distance'] = parseInt(this.getChildValue(node), 10);
-        obj['distanceUnits'] = node.getAttribute('units');
+        obj['distance'] = new ol.expr.Literal(this.getChildValue(node));
+        obj['distanceUnits'] = new ol.expr.Literal(node.getAttribute('units'));
       }
     }
   };
@@ -219,9 +225,10 @@ ol.parser.ogc.Filter_v1 = function() {
       },
       '_featureIds': function(filter) {
         var node = this.createDocumentFragment();
-        var fids = filter.getArgs();
-        for (var i = 0, ii = fids.length; i < ii; i++) {
-          this.writeNode('FeatureId', fids[i], null, node);
+        var args = filter.getArgs();
+        for (var i = 0, ii = args.length; i < ii; i++) {
+          goog.asserts.assert(args[i] instanceof ol.expr.Literal);
+          this.writeNode('FeatureId', args[i].getValue(), null, node);
         }
         return node;
       },
@@ -296,23 +303,26 @@ ol.parser.ogc.Filter_v1 = function() {
         filters[0] = filter.getLeft();
         filters[1] = filter.getRight();
         for (var i = 0; i < 2; ++i) {
-          var value = filters[i].getRight();
+          var expr = filters[i].getRight();
           if (filters[i].getOperator() === ol.expr.ComparisonOp.GTE) {
-            lower = value;
+            lower = expr;
           } else if (filters[i].getOperator() === ol.expr.ComparisonOp.LTE) {
-            upper = value;
+            upper = expr;
           }
         }
         this.writeNode('LowerBoundary', lower, null, node);
         this.writeNode('UpperBoundary', upper, null, node);
         return node;
       },
-      'PropertyName': function(name) {
+      'PropertyName': function(expr) {
+        goog.asserts.assert(expr instanceof ol.expr.Identifier);
         var node = this.createElementNS('ogc:PropertyName');
-        node.appendChild(this.createTextNode(name));
+        node.appendChild(this.createTextNode(expr.getName()));
         return node;
       },
-      'Literal': function(value) {
+      'Literal': function(expr) {
+        goog.asserts.assert(expr instanceof ol.expr.Literal);
+        var value = expr.getValue();
         if (value instanceof Date) {
           value = value.toISOString();
         }
@@ -320,14 +330,14 @@ ol.parser.ogc.Filter_v1 = function() {
         node.appendChild(this.createTextNode(value));
         return node;
       },
-      'LowerBoundary': function(value) {
+      'LowerBoundary': function(expr) {
         var node = this.createElementNS('ogc:LowerBoundary');
-        this.writeOgcExpression(value, node);
+        this.writeOgcExpression(expr, node);
         return node;
       },
-      'UpperBoundary': function(value) {
+      'UpperBoundary': function(expr) {
         var node = this.createElementNS('ogc:UpperBoundary');
-        this.writeOgcExpression(value, node);
+        this.writeOgcExpression(expr, node);
         return node;
       },
       'INTERSECTS': function(filter) {
@@ -347,8 +357,10 @@ ol.parser.ogc.Filter_v1 = function() {
       'Distance': function(filter) {
         var node = this.createElementNS('ogc:Distance');
         var args = filter.getArgs();
-        node.setAttribute('units', args[2]);
-        node.appendChild(this.createTextNode(args[1]));
+        goog.asserts.assert(args[2] instanceof ol.expr.Literal);
+        node.setAttribute('units', args[2].getValue());
+        goog.asserts.assert(args[1] instanceof ol.expr.Literal);
+        node.appendChild(this.createTextNode(args[1].getValue()));
         return node;
       },
       'Function': function(filter) {
@@ -378,14 +390,16 @@ ol.parser.ogc.Filter_v1 = function() {
     '<=': 'PropertyIsLessThanOrEqualTo',
     '>=': 'PropertyIsGreaterThanOrEqualTo',
     '..': 'PropertyIsBetween',
-    '~': 'PropertyIsLike',
-    'NULL': 'PropertyIsNull',
-    'BBOX': 'BBOX',
-    'DWITHIN': 'DWITHIN',
-    'WITHIN': 'WITHIN',
-    'CONTAINS': 'CONTAINS',
-    'INTERSECTS': 'INTERSECTS',
-    'FID': '_featureIds'
+    'like': 'PropertyIsLike',
+    'null': 'PropertyIsNull',
+    'extent': 'BBOX',
+    'dwithin': 'DWITHIN',
+    'within': 'WITHIN',
+    'contains': 'CONTAINS',
+    'intersects': 'INTERSECTS',
+    'fid': '_featureIds',
+    'ieq': 'PropertyIsEqualTo',
+    'ineq': 'PropertyIsNotEqualTo'
   };
   goog.base(this);
 };
@@ -402,46 +416,30 @@ ol.parser.ogc.Filter_v1.prototype.getFilterType_ = function(filter) {
   if (filter instanceof ol.expr.Logical ||
       filter instanceof ol.expr.Comparison) {
     type = filter.getOperator();
+    var left = filter.getLeft();
+    var right = filter.getRight();
     var isNull = (type === ol.expr.ComparisonOp.EQ &&
-        filter.getRight() === null);
+        right instanceof ol.expr.Literal && right.getValue() === null);
     if (isNull) {
-      type = 'NULL';
+      type = 'null';
     }
     var isBetween = (type === ol.expr.LogicalOp.AND &&
-        filter.getLeft() instanceof ol.expr.Comparison &&
-        filter.getRight() instanceof ol.expr.Comparison &&
-        filter.getLeft().getLeft() === filter.getRight().getLeft() &&
-        (filter.getLeft().getOperator() === ol.expr.ComparisonOp.LTE ||
-            filter.getLeft().getOperator() === ol.expr.ComparisonOp.GTE) &&
-        (filter.getRight().getOperator() === ol.expr.ComparisonOp.LTE ||
-            filter.getRight().getOperator() === ol.expr.ComparisonOp.GTE));
+        left instanceof ol.expr.Comparison &&
+        right instanceof ol.expr.Comparison &&
+        left.getLeft() instanceof ol.expr.Identifier &&
+        right.getLeft() instanceof ol.expr.Identifier &&
+        left.getLeft().getName() === right.getLeft().getName() &&
+        (left.getOperator() === ol.expr.ComparisonOp.LTE ||
+            left.getOperator() === ol.expr.ComparisonOp.GTE) &&
+        (right.getOperator() === ol.expr.ComparisonOp.LTE ||
+            right.getOperator() === ol.expr.ComparisonOp.GTE));
     if (isBetween) {
       type = '..';
     }
   } else if (filter instanceof ol.expr.Call) {
-    var callee = filter.getCallee().getName();
-    if (callee === ol.expr.functions.FID) {
-      type = 'FID';
-    }
-    else if (callee === ol.expr.functions.IEQ) {
-      type = '==';
-    } else if (callee === ol.expr.functions.INEQ) {
-      type = '!=';
-    }
-    else if (callee === ol.expr.functions.LIKE) {
-      type = '~';
-    }
-    else if (callee === ol.expr.functions.CONTAINS) {
-      type = 'CONTAINS';
-    } else if (callee === ol.expr.functions.WITHIN) {
-      type = 'WITHIN';
-    } else if (callee === ol.expr.functions.DWITHIN) {
-      type = 'DWITHIN';
-    } else if (callee === ol.expr.functions.EXTENT) {
-      type = 'BBOX';
-    } else if (callee === ol.expr.functions.INTERSECTS) {
-      type = 'INTERSECTS';
-    }
+    var callee = filter.getCallee();
+    goog.asserts.assert(callee instanceof ol.expr.Identifier);
+    type = callee.getName();
   } else if (filter instanceof ol.expr.Not) {
     type = '!';
   }
@@ -484,16 +482,18 @@ ol.parser.ogc.Filter_v1.prototype.write = function(filter) {
 
 
 /**
- * @param {ol.expr.Call|string|number} value The value write out.
+ * @param {ol.expr.Expression} expr The value write out.
  * @param {Element} node The node to append to.
  * @return {Element} The node to which was appended.
  * @protected
  */
-ol.parser.ogc.Filter_v1.prototype.writeOgcExpression = function(value, node) {
-  if (value instanceof ol.expr.Call) {
-    this.writeNode('Function', value, null, node);
-  } else {
-    this.writeNode('Literal', value, null, node);
+ol.parser.ogc.Filter_v1.prototype.writeOgcExpression = function(expr, node) {
+  if (expr instanceof ol.expr.Call) {
+    this.writeNode('Function', expr, null, node);
+  } else if (expr instanceof ol.expr.Literal) {
+    this.writeNode('Literal', expr, null, node);
+  } else if (expr instanceof ol.expr.Identifier) {
+    this.writeNode('PropertyName', expr, null, node);
   }
   return node;
 };
@@ -540,7 +540,7 @@ ol.parser.ogc.Filter_v1.prototype.aggregateLogical_ = function(filters,
       if (subFilters.length === 2) {
         newFilters.push(new ol.expr.Logical(operator,
             subFilters[0], subFilters[1]));
-        goog.array.clear(subFilters);
+        subFilters.length = 0;
       }
     }
     // there could be a single item left now
diff --git a/src/ol/parser/ogc/filter_v1_0_0.js b/src/ol/parser/ogc/filter_v1_0_0.js
index 7bbc07f568..bcf2874935 100644
--- a/src/ol/parser/ogc/filter_v1_0_0.js
+++ b/src/ol/parser/ogc/filter_v1_0_0.js
@@ -1,11 +1,13 @@
 goog.provide('ol.parser.ogc.Filter_v1_0_0');
 
+goog.require('goog.asserts');
 goog.require('goog.object');
 goog.require('ol.expr');
 goog.require('ol.expr.Call');
 goog.require('ol.expr.Comparison');
 goog.require('ol.expr.ComparisonOp');
 goog.require('ol.expr.Identifier');
+goog.require('ol.expr.Literal');
 goog.require('ol.expr.functions');
 goog.require('ol.geom.Geometry');
 goog.require('ol.parser.ogc.Filter_v1');
@@ -44,10 +46,9 @@ ol.parser.ogc.Filter_v1_0_0 = function() {
       this.readChildNodes(node, container);
       var args = [];
       args.push(container['property'], container['value'],
-          node.getAttribute('wildCard'),
-          node.getAttribute('singleChar'),
-          node.getAttribute('escape')
-      );
+          new ol.expr.Literal(node.getAttribute('wildCard')),
+          new ol.expr.Literal(node.getAttribute('singleChar')),
+          new ol.expr.Literal(node.getAttribute('escape')));
       obj['filters'].push(new ol.expr.Call(
           new ol.expr.Identifier(ol.expr.functions.LIKE), args));
     }
@@ -56,27 +57,26 @@ ol.parser.ogc.Filter_v1_0_0 = function() {
     'PropertyIsEqualTo': function(filter) {
       var node = this.createElementNS('ogc:PropertyIsEqualTo');
       var property = filter.getLeft();
-      if (goog.isDef(property)) {
-        this.writeNode('PropertyName', property, null, node);
-      }
+      this.writeNode('PropertyName', property, null, node);
       this.writeOgcExpression(filter.getRight(), node);
       return node;
     },
     'PropertyIsNotEqualTo': function(filter) {
       var node = this.createElementNS('ogc:PropertyIsNotEqualTo');
       var property = filter.getLeft();
-      if (goog.isDef(property)) {
-        this.writeNode('PropertyName', property, null, node);
-      }
+      this.writeNode('PropertyName', property, null, node);
       this.writeOgcExpression(filter.getRight(), node);
       return node;
     },
     'PropertyIsLike': function(filter) {
       var node = this.createElementNS('ogc:PropertyIsLike');
       var args = filter.getArgs();
-      node.setAttribute('wildCard', args[2]);
-      node.setAttribute('singleChar', args[3]);
-      node.setAttribute('escape', args[4]);
+      goog.asserts.assert(args[2] instanceof ol.expr.Literal);
+      node.setAttribute('wildCard', args[2].getValue());
+      goog.asserts.assert(args[3] instanceof ol.expr.Literal);
+      node.setAttribute('singleChar', args[3].getValue());
+      goog.asserts.assert(args[4] instanceof ol.expr.Literal);
+      node.setAttribute('escape', args[4].getValue());
       var property = args[0];
       if (goog.isDef(property)) {
         this.writeNode('PropertyName', property, null, node);
@@ -87,8 +87,14 @@ ol.parser.ogc.Filter_v1_0_0 = function() {
     'BBOX': function(filter) {
       var node = this.createElementNS('ogc:BBOX');
       var args = filter.getArgs();
-      var property = args[5], bbox = [args[0], args[1], args[2], args[3]],
-          projection = args[4];
+      goog.asserts.assert(args[0] instanceof ol.expr.Literal);
+      goog.asserts.assert(args[1] instanceof ol.expr.Literal);
+      goog.asserts.assert(args[2] instanceof ol.expr.Literal);
+      goog.asserts.assert(args[3] instanceof ol.expr.Literal);
+      goog.asserts.assert(args[4] instanceof ol.expr.Literal);
+      var property = args[5], bbox = [args[0].getValue(), args[1].getValue(),
+            args[2].getValue(), args[3].getValue()],
+          projection = args[4].getValue();
       // PropertyName is mandatory in 1.0.0, but e.g. GeoServer also
       // accepts filters without it.
       if (goog.isDefAndNotNull(property)) {
@@ -119,12 +125,17 @@ ol.parser.ogc.Filter_v1_0_0.prototype.writeSpatial_ = function(filter, name) {
   var node = this.createElementNS('ogc:' + name);
   var args = filter.getArgs();
   var property, geom = null, bbox, call, projection;
-  if (goog.isNumber(args[0])) {
-    bbox = [args[0], args[1], args[2], args[3]];
+  if (args[0] instanceof ol.expr.Literal && goog.isNumber(args[0].getValue())) {
+    goog.asserts.assert(args[1] instanceof ol.expr.Literal);
+    goog.asserts.assert(args[2] instanceof ol.expr.Literal);
+    goog.asserts.assert(args[3] instanceof ol.expr.Literal);
+    bbox = [args[0].getValue(), args[1].getValue(), args[2].getValue(),
+          args[3].getValue()];
     projection = args[4];
     property = args[5];
-  } else if (args[0] instanceof ol.geom.Geometry) {
-    geom = args[0];
+  } else if (args[0] instanceof ol.expr.Literal &&
+      args[0].getValue() instanceof ol.geom.Geometry) {
+    geom = args[0].getValue();
     if (name === 'DWithin') {
       projection = args[3];
       property = args[4];
@@ -157,8 +168,9 @@ ol.parser.ogc.Filter_v1_0_0.prototype.writeSpatial_ = function(filter, name) {
           'http://www.opengis.net/gml');
     }
     if (goog.isDef(child)) {
-      if (goog.isDef(projection)) {
-        child.setAttribute('srsName', projection);
+      goog.asserts.assert(projection instanceof ol.expr.Literal);
+      if (goog.isDefAndNotNull(projection.getValue())) {
+        child.setAttribute('srsName', projection.getValue());
       }
       node.appendChild(child);
     }
diff --git a/src/ol/parser/ogc/filter_v1_1_0.js b/src/ol/parser/ogc/filter_v1_1_0.js
index 6cfa18ed44..a54813efb7 100644
--- a/src/ol/parser/ogc/filter_v1_1_0.js
+++ b/src/ol/parser/ogc/filter_v1_1_0.js
@@ -1,11 +1,13 @@
 goog.provide('ol.parser.ogc.Filter_v1_1_0');
 
+goog.require('goog.asserts');
 goog.require('goog.object');
 goog.require('ol.expr');
 goog.require('ol.expr.Call');
 goog.require('ol.expr.Comparison');
 goog.require('ol.expr.ComparisonOp');
 goog.require('ol.expr.Identifier');
+goog.require('ol.expr.Literal');
 goog.require('ol.expr.functions');
 goog.require('ol.geom.Geometry');
 goog.require('ol.parser.ogc.Filter_v1');
@@ -59,10 +61,10 @@ ol.parser.ogc.Filter_v1_1_0 = function() {
       this.readChildNodes(node, container);
       var args = [];
       args.push(container['property'], container['value'],
-          node.getAttribute('wildCard'),
-          node.getAttribute('singleChar'),
-          node.getAttribute('escapeChar'),
-          node.getAttribute('matchCase'));
+          new ol.expr.Literal(node.getAttribute('wildCard')),
+          new ol.expr.Literal(node.getAttribute('singleChar')),
+          new ol.expr.Literal(node.getAttribute('escapeChar')),
+          new ol.expr.Literal(node.getAttribute('matchCase')));
       obj['filters'].push(new ol.expr.Call(
           new ol.expr.Identifier(ol.expr.functions.LIKE), args));
     }
@@ -103,11 +105,15 @@ ol.parser.ogc.Filter_v1_1_0 = function() {
     'PropertyIsLike': function(filter) {
       var node = this.createElementNS('ogc:PropertyIsLike');
       var args = filter.getArgs();
-      node.setAttribute('wildCard', args[2]);
-      node.setAttribute('singleChar', args[3]);
-      node.setAttribute('escapeChar', args[4]);
+      goog.asserts.assert(args[2] instanceof ol.expr.Literal);
+      goog.asserts.assert(args[3] instanceof ol.expr.Literal);
+      goog.asserts.assert(args[4] instanceof ol.expr.Literal);
+      node.setAttribute('wildCard', args[2].getValue());
+      node.setAttribute('singleChar', args[3].getValue());
+      node.setAttribute('escapeChar', args[4].getValue());
       if (goog.isDefAndNotNull(args[5])) {
-        node.setAttribute('matchCase', args[5]);
+        goog.asserts.assert(args[5] instanceof ol.expr.Literal);
+        node.setAttribute('matchCase', args[5].getValue());
       }
       var property = args[0];
       if (goog.isDef(property)) {
@@ -119,8 +125,14 @@ ol.parser.ogc.Filter_v1_1_0 = function() {
     'BBOX': function(filter) {
       var node = this.createElementNS('ogc:BBOX');
       var args = filter.getArgs();
-      var property = args[5], bbox = [args[0], args[1], args[2], args[3]],
-          projection = args[4];
+      goog.asserts.assert(args[0] instanceof ol.expr.Literal);
+      goog.asserts.assert(args[1] instanceof ol.expr.Literal);
+      goog.asserts.assert(args[2] instanceof ol.expr.Literal);
+      goog.asserts.assert(args[3] instanceof ol.expr.Literal);
+      goog.asserts.assert(args[4] instanceof ol.expr.Literal);
+      var property = args[5], bbox = [args[0].getValue(), args[1].getValue(),
+            args[2].getValue(), args[3].getValue()],
+          projection = args[4].getValue();
       // PropertyName is optional in 1.1.0
       if (goog.isDefAndNotNull(property)) {
         this.writeNode('PropertyName', property, null, node);
@@ -143,8 +155,10 @@ ol.parser.ogc.Filter_v1_1_0 = function() {
     'SortProperty': function(sortProperty) {
       var node = this.createElementNS('ogc:SortProperty');
       this.writeNode('PropertyName', sortProperty['property'], null, node);
+      goog.asserts.assert(sortProperty['order'] instanceof ol.expr.Literal);
       this.writeNode('SortOrder',
-          (sortProperty['order'] == 'DESC') ? 'DESC' : 'ASC', null, node);
+          (sortProperty['order'].getValue() == 'DESC') ? 'DESC' : 'ASC', null,
+          node);
       return node;
     },
     'SortOrder': function(value) {
@@ -169,12 +183,17 @@ ol.parser.ogc.Filter_v1_1_0.prototype.writeSpatial_ = function(filter, name) {
   var node = this.createElementNS('ogc:' + name);
   var args = filter.getArgs();
   var property, geom = null, bbox, call, projection;
-  if (goog.isNumber(args[0])) {
-    bbox = [args[0], args[1], args[2], args[3]];
+  if (args[0] instanceof ol.expr.Literal && goog.isNumber(args[0].getValue())) {
+    goog.asserts.assert(args[1] instanceof ol.expr.Literal);
+    goog.asserts.assert(args[2] instanceof ol.expr.Literal);
+    goog.asserts.assert(args[3] instanceof ol.expr.Literal);
+    bbox = [args[0].getValue(), args[1].getValue(), args[2].getValue(),
+          args[3].getValue()];
     projection = args[4];
     property = args[5];
-  } else if (args[0] instanceof ol.geom.Geometry) {
-    geom = args[0];
+  } else if (args[0] instanceof ol.expr.Literal &&
+      args[0].getValue() instanceof ol.geom.Geometry) {
+    geom = args[0].getValue();
     if (name === 'DWithin') {
       projection = args[3];
       property = args[4];
@@ -207,8 +226,9 @@ ol.parser.ogc.Filter_v1_1_0.prototype.writeSpatial_ = function(filter, name) {
           'http://www.opengis.net/gml');
     }
     if (goog.isDef(child)) {
-      if (goog.isDef(projection)) {
-        child.setAttribute('srsName', projection);
+      goog.asserts.assert(projection instanceof ol.expr.Literal);
+      if (goog.isDefAndNotNull(projection.getValue())) {
+        child.setAttribute('srsName', projection.getValue());
       }
       node.appendChild(child);
     }
diff --git a/test/spec/ol/parser/ogc/filter_v1_0_0.test.js b/test/spec/ol/parser/ogc/filter_v1_0_0.test.js
index 3c413c75ca..43aaa54201 100644
--- a/test/spec/ol/parser/ogc/filter_v1_0_0.test.js
+++ b/test/spec/ol/parser/ogc/filter_v1_0_0.test.js
@@ -11,12 +11,12 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = parser.read(xml);
         expect(filter instanceof ol.expr.Call).to.be(true);
-        expect(filter.getCallee().getName()).to.eql(
+        expect(filter.getCallee().getName()).to.equal(
             ol.expr.functions.INTERSECTS);
         var args = filter.getArgs();
         var geom = args[0];
-        expect(geom instanceof ol.geom.Polygon).to.be(true);
-        expect(args[2]).to.eql('Geometry');
+        expect(geom.getValue() instanceof ol.geom.Polygon).to.be(true);
+        expect(args[2].getName()).to.equal('Geometry');
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -28,11 +28,11 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = parser.read(xml);
         expect(filter instanceof ol.expr.Call).to.be(true);
-        expect(filter.getCallee().getName()).to.eql(ol.expr.functions.WITHIN);
+        expect(filter.getCallee().getName()).to.equal(ol.expr.functions.WITHIN);
         var args = filter.getArgs();
         var geom = args[0];
-        expect(geom instanceof ol.geom.Polygon).to.be(true);
-        expect(args[2]).to.eql('Geometry');
+        expect(geom.getValue() instanceof ol.geom.Polygon).to.be(true);
+        expect(args[2].getName()).to.equal('Geometry');
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -44,12 +44,12 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = parser.read(xml);
         expect(filter instanceof ol.expr.Call).to.be(true);
-        expect(filter.getCallee().getName()).to.eql(
+        expect(filter.getCallee().getName()).to.equal(
             ol.expr.functions.CONTAINS);
         var args = filter.getArgs();
         var geom = args[0];
-        expect(geom instanceof ol.geom.Polygon).to.be(true);
-        expect(args[2]).to.eql('Geometry');
+        expect(geom.getValue() instanceof ol.geom.Polygon).to.be(true);
+        expect(args[2].getName()).to.equal('Geometry');
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -61,16 +61,17 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = parser.read(xml);
         expect(filter instanceof ol.expr.Logical).to.be.ok();
-        expect(filter.getOperator()).to.eql(ol.expr.LogicalOp.AND);
+        expect(filter.getOperator()).to.equal(ol.expr.LogicalOp.AND);
         expect(filter.getLeft() instanceof ol.expr.Comparison).to.be.ok();
-        expect(filter.getLeft().getOperator()).to.eql(ol.expr.ComparisonOp.GTE);
-        expect(filter.getLeft().getLeft()).to.eql('number');
-        expect(filter.getLeft().getRight()).to.eql(0);
+        expect(filter.getLeft().getOperator()).to.equal(
+            ol.expr.ComparisonOp.GTE);
+        expect(filter.getLeft().getLeft().getName()).to.equal('number');
+        expect(filter.getLeft().getRight().getValue()).to.equal(0);
         expect(filter.getRight() instanceof ol.expr.Comparison).to.be.ok();
-        expect(filter.getRight().getOperator()).to.eql(
+        expect(filter.getRight().getOperator()).to.equal(
             ol.expr.ComparisonOp.LTE);
-        expect(filter.getRight().getLeft()).to.eql('number');
-        expect(filter.getRight().getRight()).to.eql(100);
+        expect(filter.getRight().getLeft().getName()).to.equal('number');
+        expect(filter.getRight().getRight().getValue()).to.equal(100);
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -82,16 +83,17 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = parser.read(xml);
         expect(filter instanceof ol.expr.Logical).to.be.ok();
-        expect(filter.getOperator()).to.eql(ol.expr.LogicalOp.AND);
+        expect(filter.getOperator()).to.equal(ol.expr.LogicalOp.AND);
         expect(filter.getLeft() instanceof ol.expr.Comparison).to.be.ok();
-        expect(filter.getLeft().getOperator()).to.eql(ol.expr.ComparisonOp.GTE);
-        expect(filter.getLeft().getLeft()).to.eql('number');
-        expect(filter.getLeft().getRight()).to.eql(0);
+        expect(filter.getLeft().getOperator()).to.equal(
+            ol.expr.ComparisonOp.GTE);
+        expect(filter.getLeft().getLeft().getName()).to.equal('number');
+        expect(filter.getLeft().getRight().getValue()).to.equal(0);
         expect(filter.getRight() instanceof ol.expr.Comparison).to.be.ok();
-        expect(filter.getRight().getOperator()).to.eql(
+        expect(filter.getRight().getOperator()).to.equal(
             ol.expr.ComparisonOp.LTE);
-        expect(filter.getRight().getLeft()).to.eql('number');
-        expect(filter.getRight().getRight()).to.eql(100);
+        expect(filter.getRight().getLeft().getName()).to.equal('number');
+        expect(filter.getRight().getRight().getValue()).to.equal(100);
         done();
       });
     });
@@ -101,8 +103,8 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = parser.read(xml);
         expect(filter instanceof ol.expr.Comparison).to.be.ok();
-        expect(filter.getLeft()).to.eql('prop');
-        expect(filter.getRight()).to.eql(null);
+        expect(filter.getLeft().getName()).to.equal('prop');
+        expect(filter.getRight().getValue()).to.equal(null);
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -114,7 +116,10 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = new ol.expr.Call(
             new ol.expr.Identifier(ol.expr.functions.EXTENT),
-            [-180, -90, 180, 90, 'EPSG:4326', 'the_geom']);
+            [new ol.expr.Literal(-180), new ol.expr.Literal(-90),
+              new ol.expr.Literal(180), new ol.expr.Literal(90),
+              new ol.expr.Literal('EPSG:4326'),
+              new ol.expr.Identifier('the_geom')]);
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -126,7 +131,9 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = new ol.expr.Call(
             new ol.expr.Identifier(ol.expr.functions.EXTENT),
-            [-180, -90, 180, 90, 'EPSG:4326']);
+            [new ol.expr.Literal(-180), new ol.expr.Literal(-90),
+              new ol.expr.Literal(180), new ol.expr.Literal(90),
+              new ol.expr.Literal('EPSG:4326')]);
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -138,8 +145,9 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = new ol.expr.Call(new ol.expr.Identifier(
             ol.expr.functions.DWITHIN),
-            [new ol.geom.Point([2488789, 289552]), 1000, 'm', undefined,
-             'Geometry']);
+            [new ol.expr.Literal(new ol.geom.Point([2488789, 289552])),
+              new ol.expr.Literal(1000), new ol.expr.Literal('m'),
+              new ol.expr.Literal(null), new ol.expr.Identifier('Geometry')]);
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         filter = parser.read(xml);
@@ -160,9 +168,11 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = new ol.expr.Logical(ol.expr.LogicalOp.OR,
             new ol.expr.Call(new ol.expr.Identifier(ol.expr.functions.LIKE),
-            ['person', 'me', '*', '.', '!']),
+            [new ol.expr.Identifier('person'), new ol.expr.Literal('me'),
+              new ol.expr.Literal('*'), new ol.expr.Literal('.'),
+              new ol.expr.Literal('!')]),
             new ol.expr.Call(new ol.expr.Identifier(ol.expr.functions.FID),
-            ['foo.1', 'foo.2']));
+            [new ol.expr.Literal('foo.1'), new ol.expr.Literal('foo.2')]));
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -176,9 +186,11 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
           afterLoadXml(url, function(xml) {
             var filter = new ol.expr.Logical(ol.expr.LogicalOp.AND,
                 new ol.expr.Call(new ol.expr.Identifier(ol.expr.functions.LIKE),
-                ['person', 'me', '*', '.', '!']),
+                [new ol.expr.Identifier('person'), new ol.expr.Literal('me'),
+                  new ol.expr.Literal('*'), new ol.expr.Literal('.'),
+                  new ol.expr.Literal('!')]),
                 new ol.expr.Call(new ol.expr.Identifier(ol.expr.functions.FID),
-                ['foo.1', 'foo.2']));
+                [new ol.expr.Literal('foo.1'), new ol.expr.Literal('foo.2')]));
             var output = parser.write(filter);
             expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
             done();
@@ -192,7 +204,7 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
           afterLoadXml(url, function(xml) {
             var filter = new ol.expr.Not(
                 new ol.expr.Call(new ol.expr.Identifier(ol.expr.functions.FID),
-                    ['foo.2']));
+                    [new ol.expr.Literal('foo.2')]));
             var output = parser.write(filter);
             expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
             done();
@@ -211,8 +223,10 @@ describe('ol.parser.ogc.Filter_v1_0_0', function() {
         // ISO 8601: 2011-12-27T18:19:15.123Z
         var end = new Date(Date.UTC(2011, 11, 27, 18, 19, 15, 123));
         var filter = new ol.expr.Logical(ol.expr.LogicalOp.AND,
-            new ol.expr.Comparison(ol.expr.ComparisonOp.GTE, 'when', start),
-            new ol.expr.Comparison(ol.expr.ComparisonOp.LTE, 'when', end));
+            new ol.expr.Comparison(ol.expr.ComparisonOp.GTE,
+            new ol.expr.Identifier('when'), new ol.expr.Literal(start)),
+            new ol.expr.Comparison(ol.expr.ComparisonOp.LTE,
+            new ol.expr.Identifier('when'), new ol.expr.Literal(end)));
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -229,6 +243,7 @@ goog.require('ol.expr.Call');
 goog.require('ol.expr.Comparison');
 goog.require('ol.expr.ComparisonOp');
 goog.require('ol.expr.Identifier');
+goog.require('ol.expr.Literal');
 goog.require('ol.expr.Logical');
 goog.require('ol.expr.LogicalOp');
 goog.require('ol.expr.Not');
diff --git a/test/spec/ol/parser/ogc/filter_v1_1_0.test.js b/test/spec/ol/parser/ogc/filter_v1_1_0.test.js
index 695a848d65..9d7d06bd3d 100644
--- a/test/spec/ol/parser/ogc/filter_v1_1_0.test.js
+++ b/test/spec/ol/parser/ogc/filter_v1_1_0.test.js
@@ -11,30 +11,36 @@ describe('ol.parser.ogc.Filter_v1_1_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = parser.read(xml);
         expect(filter instanceof ol.expr.Logical).to.be(true);
-        expect(filter.getOperator()).to.eql(ol.expr.LogicalOp.OR);
+        expect(filter.getOperator()).to.equal(ol.expr.LogicalOp.OR);
         var filters = [];
         parser.getSubfiltersForLogical_(filter, filters);
-        expect(filters.length).to.eql(5);
+        expect(filters.length).to.equal(5);
         expect(filters[0]).to.eql(new ol.expr.Logical(ol.expr.LogicalOp.AND,
             new ol.expr.Comparison(
-                ol.expr.ComparisonOp.GTE, 'number', 1064866676),
+                ol.expr.ComparisonOp.GTE, new ol.expr.Identifier('number'),
+                new ol.expr.Literal(1064866676)),
             new ol.expr.Comparison(
-                ol.expr.ComparisonOp.LTE, 'number', 1065512599)));
+                ol.expr.ComparisonOp.LTE, new ol.expr.Identifier('number'),
+                new ol.expr.Literal(1065512599))));
         expect(filters[1]).to.eql(new ol.expr.Not(new ol.expr.Comparison(
-            ol.expr.ComparisonOp.LTE, 'FOO', 5000)));
+            ol.expr.ComparisonOp.LTE, new ol.expr.Identifier('FOO'),
+            new ol.expr.Literal(5000))));
         expect(filters[2] instanceof ol.expr.Call).to.be(true);
-        expect(filters[2].getCallee().getName()).to.eql(
+        expect(filters[2].getCallee().getName()).to.equal(
             ol.expr.functions.LIKE);
-        expect(filters[2].getArgs()).to.eql(['cat', '*dog.food!*good', '*',
-          '.', '!', null]);
+        expect(filters[2].getArgs()).to.eql([new ol.expr.Identifier('cat'),
+              new ol.expr.Literal('*dog.food!*good'), new ol.expr.Literal('*'),
+              new ol.expr.Literal('.'), new ol.expr.Literal('!'),
+              new ol.expr.Literal(null)]);
         expect(filters[3] instanceof ol.expr.Call).to.be(true);
-        expect(filters[3].getCallee().getName()).to.eql(
+        expect(filters[3].getCallee().getName()).to.equal(
             ol.expr.functions.IEQ);
-        expect(filters[3].getArgs()).to.eql(['cat', 'dog']);
+        expect(filters[3].getArgs()).to.eql([new ol.expr.Identifier('cat'),
+              new ol.expr.Literal('dog')]);
         expect(filters[4] instanceof ol.expr.Comparison).to.be(true);
-        expect(filters[4].getOperator()).to.eql(ol.expr.ComparisonOp.EQ);
-        expect(filters[4].getLeft()).to.eql('cat');
-        expect(filters[4].getRight()).to.eql('dog');
+        expect(filters[4].getOperator()).to.equal(ol.expr.ComparisonOp.EQ);
+        expect(filters[4].getLeft().getName()).to.equal('cat');
+        expect(filters[4].getRight().getValue()).to.equal('dog');
         done();
       });
     });
@@ -109,7 +115,7 @@ describe('ol.parser.ogc.Filter_v1_1_0', function() {
         c = cases[i];
         filter = parser.read(c.str);
         var matchCase = (filter instanceof ol.expr.Call) ? false : true;
-        expect(matchCase).to.eql(c.exp);
+        expect(matchCase).to.equal(c.exp);
       }
     });
 
@@ -149,8 +155,10 @@ describe('ol.parser.ogc.Filter_v1_1_0', function() {
         var filter = new ol.expr.Call(new ol.expr.Identifier(
             ol.expr.functions.INTERSECTS),
             [new ol.expr.Call(new ol.expr.Identifier('querySingle'),
-             ['sf:restricted', 'the_geom',
-               'cat=3']), undefined, 'the_geom']);
+             [new ol.expr.Literal('sf:restricted'),
+               new ol.expr.Literal('the_geom'),
+               new ol.expr.Literal('cat=3')]), new ol.expr.Literal(null),
+             new ol.expr.Identifier('the_geom')]);
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -162,8 +170,9 @@ describe('ol.parser.ogc.Filter_v1_1_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = new ol.expr.Logical(ol.expr.LogicalOp.AND,
             new ol.expr.Call(new ol.expr.Identifier(ol.expr.functions.INEQ),
-            ['FOO', new ol.expr.Call(new ol.expr.Identifier('customFunction'),
-             ['param1', 'param2'])]));
+            [new ol.expr.Identifier('FOO'), new ol.expr.Call(
+            new ol.expr.Identifier('customFunction'),
+            [new ol.expr.Literal('param1'), new ol.expr.Literal('param2')])]));
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -177,8 +186,11 @@ describe('ol.parser.ogc.Filter_v1_1_0', function() {
             ol.expr.functions.DWITHIN),
             [new ol.expr.Call(new ol.expr.Identifier('collectGeometries'),
              [new ol.expr.Call(new ol.expr.Identifier('queryCollection'),
-              ['sf:roads', 'the_geom', 'INCLUDE'])]), 200, 'meters',
-             undefined, 'the_geom']);
+              [new ol.expr.Literal('sf:roads'),
+               new ol.expr.Literal('the_geom'),
+               new ol.expr.Literal('INCLUDE')])]), new ol.expr.Literal(200),
+              new ol.expr.Literal('meters'),
+             new ol.expr.Literal(null), new ol.expr.Identifier('the_geom')]);
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -190,7 +202,9 @@ describe('ol.parser.ogc.Filter_v1_1_0', function() {
       afterLoadXml(url, function(xml) {
         var filter = new ol.expr.Call(
             new ol.expr.Identifier(ol.expr.functions.LIKE),
-            ['person', '*me*', '*', '.', '!', false]);
+            [new ol.expr.Identifier('person'), new ol.expr.Literal('*me*'),
+             new ol.expr.Literal('*'), new ol.expr.Literal('.'),
+             new ol.expr.Literal('!'), new ol.expr.Literal(false)]);
         var output = parser.write(filter);
         expect(goog.dom.xml.loadXml(output)).to.xmleql(xml);
         done();
@@ -202,11 +216,11 @@ describe('ol.parser.ogc.Filter_v1_1_0', function() {
       afterLoadXml(url, function(xml) {
         var writer = parser.writers['http://www.opengis.net/ogc']['SortBy'];
         var output = writer.call(parser, [{
-          'property': 'Title',
-          'order': 'ASC'
+          'property': new ol.expr.Identifier('Title'),
+          'order': new ol.expr.Literal('ASC')
         },{
-          'property': 'Relevance',
-          'order': 'DESC'
+          'property': new ol.expr.Identifier('Relevance'),
+          'order': new ol.expr.Literal('DESC')
         }]);
         expect(output).to.xmleql(xml);
         done();
@@ -223,6 +237,7 @@ goog.require('ol.expr.Call');
 goog.require('ol.expr.Comparison');
 goog.require('ol.expr.ComparisonOp');
 goog.require('ol.expr.Identifier');
+goog.require('ol.expr.Literal');
 goog.require('ol.expr.Logical');
 goog.require('ol.expr.LogicalOp');
 goog.require('ol.expr.Not');