diff --git a/core-api/src/main/java/com/optimizely/ab/Optimizely.java b/core-api/src/main/java/com/optimizely/ab/Optimizely.java
index bbaec926e..02be1399a 100644
--- a/core-api/src/main/java/com/optimizely/ab/Optimizely.java
+++ b/core-api/src/main/java/com/optimizely/ab/Optimizely.java
@@ -120,7 +120,7 @@ Variation activate(@Nonnull String experimentKey,
     public @Nullable
     Variation activate(@Nonnull String experimentKey,
                        @Nonnull String userId,
-                       @Nonnull Map<String, String> attributes) throws UnknownExperimentException {
+                       @Nonnull Map<String, ?> attributes) throws UnknownExperimentException {
 
         if (experimentKey == null) {
             logger.error("The experimentKey parameter must be nonnull.");
@@ -153,7 +153,7 @@ Variation activate(@Nonnull Experiment experiment,
     public @Nullable
     Variation activate(@Nonnull Experiment experiment,
                        @Nonnull String userId,
-                       @Nonnull Map<String, String> attributes) {
+                       @Nonnull Map<String, ?> attributes) {
 
         ProjectConfig currentConfig = getProjectConfig();
 
@@ -164,7 +164,7 @@ Variation activate(@Nonnull Experiment experiment,
     Variation activate(@Nonnull ProjectConfig projectConfig,
                        @Nonnull Experiment experiment,
                        @Nonnull String userId,
-                       @Nonnull Map<String, String> attributes) {
+                       @Nonnull Map<String, ?> attributes) {
 
         if (!validateUserId(userId)){
             logger.info("Not activating user \"{}\" for experiment \"{}\".", userId, experiment.getKey());
@@ -172,7 +172,7 @@ Variation activate(@Nonnull ProjectConfig projectConfig,
         }
         // determine whether all the given attributes are present in the project config. If not, filter out the unknown
         // attributes.
-        Map<String, String> filteredAttributes = filterAttributes(projectConfig, attributes);
+        Map<String, ?> filteredAttributes = filterAttributes(projectConfig, attributes);
 
         // bucket the user to the given experiment and dispatch an impression event
         Variation variation = decisionService.getVariation(experiment, userId, filteredAttributes);
@@ -189,7 +189,7 @@ Variation activate(@Nonnull ProjectConfig projectConfig,
     private void sendImpression(@Nonnull ProjectConfig projectConfig,
                                 @Nonnull Experiment experiment,
                                 @Nonnull String userId,
-                                @Nonnull Map<String, String> filteredAttributes,
+                                @Nonnull Map<String, ?> filteredAttributes,
                                 @Nonnull Variation variation) {
         if (experiment.isRunning()) {
             LogEvent impressionEvent = eventFactory.createImpressionEvent(
@@ -228,13 +228,13 @@ public void track(@Nonnull String eventName,
 
     public void track(@Nonnull String eventName,
                       @Nonnull String userId,
-                      @Nonnull Map<String, String> attributes) throws UnknownEventTypeException {
+                      @Nonnull Map<String, ?> attributes) throws UnknownEventTypeException {
         track(eventName, userId, attributes, Collections.<String, String>emptyMap());
     }
 
     public void track(@Nonnull String eventName,
                       @Nonnull String userId,
-                      @Nonnull Map<String, String> attributes,
+                      @Nonnull Map<String, ?> attributes,
                       @Nonnull Map<String, ?> eventTags) throws UnknownEventTypeException {
 
         if (!validateUserId(userId)) {
@@ -259,7 +259,7 @@ public void track(@Nonnull String eventName,
 
         // determine whether all the given attributes are present in the project config. If not, filter out the unknown
         // attributes.
-        Map<String, String> filteredAttributes = filterAttributes(currentConfig, attributes);
+        Map<String, ?> filteredAttributes = filterAttributes(currentConfig, attributes);
 
         if (eventTags == null) {
             logger.warn("Event tags is null when non-null was expected. Defaulting to an empty event tags map.");
@@ -344,7 +344,7 @@ public void track(@Nonnull String eventName,
      */
     public @Nonnull Boolean isFeatureEnabled(@Nonnull String featureKey,
                                               @Nonnull String userId,
-                                              @Nonnull Map<String, String> attributes) {
+                                              @Nonnull Map<String, ?> attributes) {
         if (featureKey == null) {
             logger.warn("The featureKey parameter must be nonnull.");
             return false;
@@ -359,7 +359,7 @@ else if (userId == null) {
             return false;
         }
 
-        Map<String, String> filteredAttributes = filterAttributes(projectConfig, attributes);
+        Map<String, ?> filteredAttributes = filterAttributes(projectConfig, attributes);
 
         FeatureDecision featureDecision = decisionService.getVariationForFeature(featureFlag, userId, filteredAttributes);
         if (featureDecision.variation != null) {
@@ -410,7 +410,7 @@ else if (userId == null) {
     public @Nullable Boolean getFeatureVariableBoolean(@Nonnull String featureKey,
                                                        @Nonnull String variableKey,
                                                        @Nonnull String userId,
-                                                       @Nonnull Map<String, String> attributes) {
+                                                       @Nonnull Map<String, ?> attributes) {
         String variableValue = getFeatureVariableValueForType(
                 featureKey,
                 variableKey,
@@ -450,7 +450,7 @@ else if (userId == null) {
     public @Nullable Double getFeatureVariableDouble(@Nonnull String featureKey,
                                                      @Nonnull String variableKey,
                                                      @Nonnull String userId,
-                                                     @Nonnull Map<String, String> attributes) {
+                                                     @Nonnull Map<String, ?> attributes) {
         String variableValue = getFeatureVariableValueForType(
                 featureKey,
                 variableKey,
@@ -495,7 +495,7 @@ else if (userId == null) {
     public @Nullable Integer getFeatureVariableInteger(@Nonnull String featureKey,
                                                        @Nonnull String variableKey,
                                                        @Nonnull String userId,
-                                                       @Nonnull Map<String, String> attributes) {
+                                                       @Nonnull Map<String, ?> attributes) {
         String variableValue = getFeatureVariableValueForType(
                 featureKey,
                 variableKey,
@@ -540,7 +540,7 @@ else if (userId == null) {
     public @Nullable String getFeatureVariableString(@Nonnull String featureKey,
                                                      @Nonnull String variableKey,
                                                      @Nonnull String userId,
-                                                     @Nonnull Map<String, String> attributes) {
+                                                     @Nonnull Map<String, ?> attributes) {
         return getFeatureVariableValueForType(
                 featureKey,
                 variableKey,
@@ -553,7 +553,7 @@ else if (userId == null) {
     String getFeatureVariableValueForType(@Nonnull String featureKey,
                                                   @Nonnull String variableKey,
                                                   @Nonnull String userId,
-                                                  @Nonnull Map<String, String> attributes,
+                                                  @Nonnull Map<String, ?> attributes,
                                                   @Nonnull LiveVariable.VariableType variableType) {
         if (featureKey == null) {
             logger.warn("The featureKey parameter must be nonnull.");
@@ -614,7 +614,7 @@ else if (userId == null) {
      * @return List of the feature keys that are enabled for the user if the userId is empty it will
      * return Empty List.
      */
-    public List<String> getEnabledFeatures(@Nonnull String userId, @Nonnull Map<String, String> attributes) {
+    public List<String> getEnabledFeatures(@Nonnull String userId, @Nonnull Map<String, ?> attributes) {
         List<String> enabledFeaturesList = new ArrayList<String>();
 
         if (!validateUserId(userId)){
@@ -642,9 +642,9 @@ Variation getVariation(@Nonnull Experiment experiment,
     public @Nullable
     Variation getVariation(@Nonnull Experiment experiment,
                            @Nonnull String userId,
-                           @Nonnull Map<String, String> attributes) throws UnknownExperimentException {
+                           @Nonnull Map<String, ?> attributes) throws UnknownExperimentException {
 
-        Map<String, String> filteredAttributes = filterAttributes(projectConfig, attributes);
+        Map<String, ?> filteredAttributes = filterAttributes(projectConfig, attributes);
 
         return decisionService.getVariation(experiment, userId, filteredAttributes);
     }
@@ -659,7 +659,7 @@ Variation getVariation(@Nonnull String experimentKey,
     public @Nullable
     Variation getVariation(@Nonnull String experimentKey,
                            @Nonnull String userId,
-                           @Nonnull Map<String, String> attributes) {
+                           @Nonnull Map<String, ?> attributes) {
         if (!validateUserId(userId)) {
             return null;
         }
@@ -677,7 +677,7 @@ Variation getVariation(@Nonnull String experimentKey,
             return null;
         }
 
-        Map<String, String> filteredAttributes = filterAttributes(projectConfig, attributes);
+        Map<String, ?> filteredAttributes = filterAttributes(projectConfig, attributes);
 
         return decisionService.getVariation(experiment,userId,filteredAttributes);
     }
@@ -742,17 +742,18 @@ public UserProfileService getUserProfileService() {
      * @return the filtered attributes map (containing only attributes that are present in the project config) or an
      * empty map if a null attributes object is passed in
      */
-    private Map<String, String> filterAttributes(@Nonnull ProjectConfig projectConfig,
-                                                 @Nonnull Map<String, String> attributes) {
+    private Map<String, ?> filterAttributes(@Nonnull ProjectConfig projectConfig,
+                                                 @Nonnull Map<String, ?> attributes) {
         if (attributes == null) {
             logger.warn("Attributes is null when non-null was expected. Defaulting to an empty attributes map.");
             return Collections.<String, String>emptyMap();
         }
 
+        // List of attribute keys
         List<String> unknownAttributes = null;
 
         Map<String, Attribute> attributeKeyMapping = projectConfig.getAttributeKeyMapping();
-        for (Map.Entry<String, String> attribute : attributes.entrySet()) {
+        for (Map.Entry<String, ?> attribute : attributes.entrySet()) {
             if (!attributeKeyMapping.containsKey(attribute.getKey()) &&
                     !attribute.getKey().startsWith(ProjectConfig.RESERVED_ATTRIBUTE_PREFIX)) {
                 if (unknownAttributes == null) {
@@ -765,7 +766,7 @@ private Map<String, String> filterAttributes(@Nonnull ProjectConfig projectConfi
         if (unknownAttributes != null) {
             logger.warn("Attribute(s) {} not in the datafile.", unknownAttributes);
             // make a copy of the passed through attributes, then remove the unknown list
-            attributes = new HashMap<String, String>(attributes);
+            attributes = new HashMap<>(attributes);
             for (String unknownAttribute : unknownAttributes) {
                 attributes.remove(unknownAttribute);
             }
diff --git a/core-api/src/main/java/com/optimizely/ab/bucketing/DecisionService.java b/core-api/src/main/java/com/optimizely/ab/bucketing/DecisionService.java
index 0dc895feb..5083f580b 100644
--- a/core-api/src/main/java/com/optimizely/ab/bucketing/DecisionService.java
+++ b/core-api/src/main/java/com/optimizely/ab/bucketing/DecisionService.java
@@ -80,7 +80,7 @@ public DecisionService(@Nonnull Bucketer bucketer,
      */
     public @Nullable Variation getVariation(@Nonnull Experiment experiment,
                                             @Nonnull String userId,
-                                            @Nonnull Map<String, String> filteredAttributes) {
+                                            @Nonnull Map<String, ?> filteredAttributes) {
 
         if (!ExperimentUtils.isExperimentActive(experiment)) {
             return null;
@@ -129,10 +129,7 @@ public DecisionService(@Nonnull Bucketer bucketer,
         }
 
         if (ExperimentUtils.isUserInExperiment(projectConfig, experiment, filteredAttributes)) {
-            String bucketingId = userId;
-            if (filteredAttributes.containsKey(ControlAttribute.BUCKETING_ATTRIBUTE.toString())) {
-                bucketingId = filteredAttributes.get(ControlAttribute.BUCKETING_ATTRIBUTE.toString());
-            }
+            String bucketingId = getBucketingId(userId, filteredAttributes);
             variation = bucketer.bucket(experiment, bucketingId);
 
             if (variation != null) {
@@ -159,7 +156,7 @@ public DecisionService(@Nonnull Bucketer bucketer,
      */
     public @Nonnull FeatureDecision getVariationForFeature(@Nonnull FeatureFlag featureFlag,
                                                            @Nonnull String userId,
-                                                           @Nonnull Map<String, String> filteredAttributes) {
+                                                           @Nonnull Map<String, ?> filteredAttributes) {
         if (!featureFlag.getExperimentIds().isEmpty()) {
             for (String experimentId : featureFlag.getExperimentIds()) {
                 Experiment experiment = projectConfig.getExperimentIdMapping().get(experimentId);
@@ -195,7 +192,7 @@ public DecisionService(@Nonnull Bucketer bucketer,
      */
     @Nonnull FeatureDecision getVariationForFeatureInRollout(@Nonnull FeatureFlag featureFlag,
                                                              @Nonnull String userId,
-                                                             @Nonnull Map<String, String> filteredAttributes) {
+                                                             @Nonnull Map<String, ?> filteredAttributes) {
         // use rollout to get variation for feature
         if (featureFlag.getRolloutId().isEmpty()) {
             logger.info("The feature flag \"{}\" is not used in a rollout.", featureFlag.getKey());
@@ -210,10 +207,7 @@ public DecisionService(@Nonnull Bucketer bucketer,
 
         // for all rules before the everyone else rule
         int rolloutRulesLength = rollout.getExperiments().size();
-        String bucketingId = userId;
-        if (filteredAttributes.containsKey(ControlAttribute.BUCKETING_ATTRIBUTE.toString())) {
-            bucketingId = filteredAttributes.get(ControlAttribute.BUCKETING_ATTRIBUTE.toString());
-        }
+        String bucketingId = getBucketingId(userId, filteredAttributes);
         Variation variation;
         for (int i = 0; i < rolloutRulesLength - 1; i++) {
             Experiment rolloutRule = rollout.getExperiments().get(i);
@@ -343,4 +337,26 @@ void saveVariation(@Nonnull Experiment experiment,
             }
         }
     }
+
+    /**
+     * Get the bucketingId of a user if a bucketingId exists in attributes, or else default to userId.
+     * @param userId The userId of the user.
+     * @param filteredAttributes The user's attributes. This should be filtered to just attributes in the Datafile.
+     * @return bucketingId if it is a String type in attributes.
+     *      else return userId
+     */
+    String getBucketingId(@Nonnull String userId,
+                          @Nonnull Map<String, ?> filteredAttributes) {
+        String bucketingId = userId;
+        if (filteredAttributes.containsKey(ControlAttribute.BUCKETING_ATTRIBUTE.toString())) {
+            if (String.class.isInstance(filteredAttributes.get(ControlAttribute.BUCKETING_ATTRIBUTE.toString()))) {
+                bucketingId = (String) filteredAttributes.get(ControlAttribute.BUCKETING_ATTRIBUTE.toString());
+                logger.debug("BucketingId is valid: \"{}\"", bucketingId);
+            } 
+            else {
+                logger.warn("BucketingID attribute is not a string. Defaulted to userId");
+            } 
+        }
+        return bucketingId;
+    }
 }
diff --git a/core-api/src/main/java/com/optimizely/ab/config/audience/AndCondition.java b/core-api/src/main/java/com/optimizely/ab/config/audience/AndCondition.java
index 2e485b281..375205e42 100644
--- a/core-api/src/main/java/com/optimizely/ab/config/audience/AndCondition.java
+++ b/core-api/src/main/java/com/optimizely/ab/config/audience/AndCondition.java
@@ -1,6 +1,6 @@
 /**
  *
- *    Copyright 2016-2017, Optimizely and contributors
+ *    Copyright 2016-2018, Optimizely and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -36,7 +36,7 @@ public List<Condition> getConditions() {
         return conditions;
     }
 
-    public boolean evaluate(Map<String, String> attributes) {
+    public boolean evaluate(Map<String, ?> attributes) {
         for (Condition condition : conditions) {
             if (!condition.evaluate(attributes))
                 return false;
diff --git a/core-api/src/main/java/com/optimizely/ab/config/audience/Condition.java b/core-api/src/main/java/com/optimizely/ab/config/audience/Condition.java
index 3a47453e4..c84f39aef 100644
--- a/core-api/src/main/java/com/optimizely/ab/config/audience/Condition.java
+++ b/core-api/src/main/java/com/optimizely/ab/config/audience/Condition.java
@@ -1,6 +1,6 @@
 /**
  *
- *    Copyright 2016-2017, Optimizely and contributors
+ *    Copyright 2016-2018, Optimizely and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -23,5 +23,5 @@
  */
 public interface Condition {
 
-    boolean evaluate(Map<String, String> attributes);
+    boolean evaluate(Map<String, ?> attributes);
 }
\ No newline at end of file
diff --git a/core-api/src/main/java/com/optimizely/ab/config/audience/NotCondition.java b/core-api/src/main/java/com/optimizely/ab/config/audience/NotCondition.java
index 7e269c6f3..84b8c010e 100644
--- a/core-api/src/main/java/com/optimizely/ab/config/audience/NotCondition.java
+++ b/core-api/src/main/java/com/optimizely/ab/config/audience/NotCondition.java
@@ -1,6 +1,6 @@
 /**
  *
- *    Copyright 2016-2017, Optimizely and contributors
+ *    Copyright 2016-2018, Optimizely and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -37,7 +37,7 @@ public Condition getCondition() {
         return condition;
     }
 
-    public boolean evaluate(Map<String, String> attributes) {
+    public boolean evaluate(Map<String, ?> attributes) {
         return !condition.evaluate(attributes);
     }
 
diff --git a/core-api/src/main/java/com/optimizely/ab/config/audience/OrCondition.java b/core-api/src/main/java/com/optimizely/ab/config/audience/OrCondition.java
index 6e80a43e5..52a53c952 100644
--- a/core-api/src/main/java/com/optimizely/ab/config/audience/OrCondition.java
+++ b/core-api/src/main/java/com/optimizely/ab/config/audience/OrCondition.java
@@ -1,6 +1,6 @@
 /**
  *
- *    Copyright 2016-2017, Optimizely and contributors
+ *    Copyright 2016-2018, Optimizely and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -36,7 +36,7 @@ public List<Condition> getConditions() {
         return conditions;
     }
 
-    public boolean evaluate(Map<String, String> attributes) {
+    public boolean evaluate(Map<String, ?> attributes) {
         for (Condition condition : conditions) {
             if (condition.evaluate(attributes))
                 return true;
diff --git a/core-api/src/main/java/com/optimizely/ab/config/audience/UserAttribute.java b/core-api/src/main/java/com/optimizely/ab/config/audience/UserAttribute.java
index 3827291bd..c8627a4a1 100644
--- a/core-api/src/main/java/com/optimizely/ab/config/audience/UserAttribute.java
+++ b/core-api/src/main/java/com/optimizely/ab/config/audience/UserAttribute.java
@@ -1,6 +1,6 @@
 /**
  *
- *    Copyright 2016-2017, Optimizely and contributors
+ *    Copyright 2016-2018, Optimizely and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -29,9 +29,9 @@ public class UserAttribute implements Condition {
 
     private final String name;
     private final String type;
-    private final String value;
+    private final Object value;
 
-    public UserAttribute(@Nonnull String name, @Nonnull String type, @Nullable String value) {
+    public UserAttribute(@Nonnull String name, @Nonnull String type, @Nullable Object value) {
         this.name = name;
         this.type = type;
         this.value = value;
@@ -45,12 +45,13 @@ public String getType() {
         return type;
     }
 
-    public String getValue() {
+    public Object getValue() {
         return value;
     }
 
-    public boolean evaluate(Map<String, String> attributes) {
-        String userAttributeValue = attributes.get(name);
+    public boolean evaluate(Map<String, ?> attributes) {
+        // Valid for primative types, but needs to change when a value is an object or an array
+        Object userAttributeValue = attributes.get(name);
 
         if (value != null) { // if there is a value in the condition
             // check user attribute value is equal
@@ -69,7 +70,7 @@ else if (userAttributeValue != null) { // if the datafile value is null but user
     public String toString() {
         return "{name='" + name + "\'" +
                ", type='" + type + "\'" +
-               ", value='" + value + "\'" +
+               ", value='" + value.toString() + "\'" +
                "}";
     }
 
diff --git a/core-api/src/main/java/com/optimizely/ab/event/internal/EventFactory.java b/core-api/src/main/java/com/optimizely/ab/event/internal/EventFactory.java
index a7aedda50..ba347e7af 100644
--- a/core-api/src/main/java/com/optimizely/ab/event/internal/EventFactory.java
+++ b/core-api/src/main/java/com/optimizely/ab/event/internal/EventFactory.java
@@ -62,7 +62,7 @@ public LogEvent createImpressionEvent(@Nonnull ProjectConfig projectConfig,
                                           @Nonnull Experiment activatedExperiment,
                                           @Nonnull Variation variation,
                                           @Nonnull String userId,
-                                          @Nonnull Map<String, String> attributes) {
+                                          @Nonnull Map<String, ?> attributes) {
 
         Decision decision = new Decision.Builder()
                 .setCampaignId(activatedExperiment.getLayerId())
@@ -108,7 +108,7 @@ public LogEvent createConversionEvent(@Nonnull ProjectConfig projectConfig,
                                           @Nonnull String userId,
                                           @Nonnull String eventId, // Why is this not used?
                                           @Nonnull String eventName,
-                                          @Nonnull Map<String, String> attributes,
+                                          @Nonnull Map<String, ?> attributes,
                                           @Nonnull Map<String, ?> eventTags) {
 
         if (experimentVariationMap.isEmpty()) {
@@ -164,10 +164,10 @@ public LogEvent createConversionEvent(@Nonnull ProjectConfig projectConfig,
         return new LogEvent(LogEvent.RequestMethod.POST, EVENT_ENDPOINT, Collections.<String, String>emptyMap(), eventBatch);
     }
 
-    private List<Attribute> buildAttributeList(ProjectConfig projectConfig, Map<String, String> attributes) {
+    private List<Attribute> buildAttributeList(ProjectConfig projectConfig, Map<String, ?> attributes) {
         List<Attribute> attributesList = new ArrayList<Attribute>();
 
-        for (Map.Entry<String, String> entry : attributes.entrySet()) {
+        for (Map.Entry<String, ?> entry : attributes.entrySet()) {
             String attributeId = projectConfig.getAttributeId(projectConfig, entry.getKey());
             if(attributeId == null) {
                 continue;
diff --git a/core-api/src/main/java/com/optimizely/ab/internal/ExperimentUtils.java b/core-api/src/main/java/com/optimizely/ab/internal/ExperimentUtils.java
index a0ba4b99b..5ca27449e 100644
--- a/core-api/src/main/java/com/optimizely/ab/internal/ExperimentUtils.java
+++ b/core-api/src/main/java/com/optimizely/ab/internal/ExperimentUtils.java
@@ -1,6 +1,6 @@
 /**
  *
- *    Copyright 2017, Optimizely and contributors
+ *    Copyright 2017-2018, Optimizely and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -58,7 +58,7 @@ public static boolean isExperimentActive(@Nonnull Experiment experiment) {
      */
     public static boolean isUserInExperiment(@Nonnull ProjectConfig projectConfig,
                                              @Nonnull Experiment experiment,
-                                             @Nonnull Map<String, String> attributes) {
+                                             @Nonnull Map<String, ?> attributes) {
         List<String> experimentAudienceIds = experiment.getAudienceIds();
 
         // if there are no audiences, ALL users should be part of the experiment
diff --git a/core-api/src/main/java/com/optimizely/ab/notification/ActivateNotificationListener.java b/core-api/src/main/java/com/optimizely/ab/notification/ActivateNotificationListener.java
index 883bb6963..973c5d1ec 100644
--- a/core-api/src/main/java/com/optimizely/ab/notification/ActivateNotificationListener.java
+++ b/core-api/src/main/java/com/optimizely/ab/notification/ActivateNotificationListener.java
@@ -1,6 +1,6 @@
 /**
  *
- *    Copyright 2017, Optimizely and contributors
+ *    Copyright 2017-2018, Optimizely and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -38,7 +38,7 @@ public final void notify(Object... args) {
         assert(args[1] instanceof String);
         String userId = (String) args[1];
         assert(args[2] instanceof java.util.Map);
-        Map<String, String> attributes = (Map<String, String>) args[2];
+        Map<String, ?> attributes = (Map<String, ?>) args[2];
         assert(args[3] instanceof Variation);
         Variation variation = (Variation) args[3];
         assert(args[4] instanceof LogEvent);
@@ -57,7 +57,7 @@ public final void notify(Object... args) {
      */
     public abstract void onActivate(@Nonnull Experiment experiment,
                              @Nonnull String userId,
-                             @Nonnull Map<String, String> attributes,
+                             @Nonnull Map<String, ?> attributes,
                              @Nonnull Variation variation,
                              @Nonnull LogEvent event) ;
 
diff --git a/core-api/src/main/java/com/optimizely/ab/notification/ActivateNotificationListenerInterface.java b/core-api/src/main/java/com/optimizely/ab/notification/ActivateNotificationListenerInterface.java
index fdae1fc5d..866fa5a80 100644
--- a/core-api/src/main/java/com/optimizely/ab/notification/ActivateNotificationListenerInterface.java
+++ b/core-api/src/main/java/com/optimizely/ab/notification/ActivateNotificationListenerInterface.java
@@ -18,7 +18,7 @@ public interface ActivateNotificationListenerInterface {
      */
     public void onActivate(@Nonnull Experiment experiment,
                                     @Nonnull String userId,
-                                    @Nonnull Map<String, String> attributes,
+                                    @Nonnull Map<String, ?> attributes,
                                     @Nonnull Variation variation,
                                     @Nonnull LogEvent event) ;
 
diff --git a/core-api/src/main/java/com/optimizely/ab/notification/NotificationCenter.java b/core-api/src/main/java/com/optimizely/ab/notification/NotificationCenter.java
index 9b68c75ba..495ebac68 100644
--- a/core-api/src/main/java/com/optimizely/ab/notification/NotificationCenter.java
+++ b/core-api/src/main/java/com/optimizely/ab/notification/NotificationCenter.java
@@ -94,7 +94,7 @@ public int addActivateNotificationListener(final ActivateNotificationListenerInt
         else {
             return addNotificationListener(NotificationType.Activate, new ActivateNotificationListener() {
                 @Override
-                public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, String> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
+                public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, ?> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
                     activateNotificationListenerInterface.onActivate(experiment, userId, attributes, variation, event);
                 }
             });
@@ -113,7 +113,7 @@ public int addTrackNotificationListener(final TrackNotificationListenerInterface
         else {
             return addNotificationListener(NotificationType.Track, new TrackNotificationListener() {
                 @Override
-                public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull Map<String, String> attributes, @Nonnull Map<String, ?> eventTags, @Nonnull LogEvent event) {
+                public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull Map<String, ?> attributes, @Nonnull Map<String, ?> eventTags, @Nonnull LogEvent event) {
                     trackNotificationListenerInterface.onTrack(eventKey, userId, attributes, eventTags, event);
                 }
             });
diff --git a/core-api/src/main/java/com/optimizely/ab/notification/TrackNotificationListener.java b/core-api/src/main/java/com/optimizely/ab/notification/TrackNotificationListener.java
index 16809f716..c45759efc 100644
--- a/core-api/src/main/java/com/optimizely/ab/notification/TrackNotificationListener.java
+++ b/core-api/src/main/java/com/optimizely/ab/notification/TrackNotificationListener.java
@@ -1,6 +1,6 @@
 /**
  *
- *    Copyright 2017, Optimizely and contributors
+ *    Copyright 2017-2018, Optimizely and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -36,7 +36,7 @@ public final void notify(Object... args) {
         assert(args[1] instanceof String);
         String userId = (String) args[1];
         assert(args[2] instanceof java.util.Map);
-        Map<String, String> attributes = (Map<String, String>) args[2];
+        Map<String, ?> attributes = (Map<String, ?>) args[2];
         assert(args[3] instanceof java.util.Map);
         Map<String, ?> eventTags = (Map<String, ?>) args[3];
         assert(args[4] instanceof LogEvent);
@@ -55,7 +55,7 @@ public final void notify(Object... args) {
      */
     public abstract void onTrack(@Nonnull String eventKey,
                           @Nonnull String userId,
-                          @Nonnull Map<String, String> attributes,
+                          @Nonnull Map<String, ?> attributes,
                           @Nonnull Map<String, ?>  eventTags,
                           @Nonnull LogEvent event) ;
 }
diff --git a/core-api/src/main/java/com/optimizely/ab/notification/TrackNotificationListenerInterface.java b/core-api/src/main/java/com/optimizely/ab/notification/TrackNotificationListenerInterface.java
index 74df611dd..7a7f22c4e 100644
--- a/core-api/src/main/java/com/optimizely/ab/notification/TrackNotificationListenerInterface.java
+++ b/core-api/src/main/java/com/optimizely/ab/notification/TrackNotificationListenerInterface.java
@@ -16,7 +16,7 @@ public interface TrackNotificationListenerInterface {
      */
     public void onTrack(@Nonnull String eventKey,
                                  @Nonnull String userId,
-                                 @Nonnull Map<String, String> attributes,
+                                 @Nonnull Map<String, ?> attributes,
                                  @Nonnull Map<String, ?>  eventTags,
                                  @Nonnull LogEvent event) ;
 
diff --git a/core-api/src/test/java/com/optimizely/ab/OptimizelyTest.java b/core-api/src/test/java/com/optimizely/ab/OptimizelyTest.java
index b121624c6..a29a1fa12 100644
--- a/core-api/src/test/java/com/optimizely/ab/OptimizelyTest.java
+++ b/core-api/src/test/java/com/optimizely/ab/OptimizelyTest.java
@@ -524,7 +524,7 @@ public void activateWithAttributes() throws Exception {
         Experiment activatedExperiment = validProjectConfig.getExperiments().get(0);
         Variation bucketedVariation = activatedExperiment.getVariations().get(0);
         Variation userIdBucketedVariation = activatedExperiment.getVariations().get(1);
-        Attribute attribute = validProjectConfig.getAttributes().get(0);
+        Attribute attributeString = validProjectConfig.getAttributes().get(0); 
 
         // setup a mock event builder to return expected impression params
         EventFactory mockEventFactory = mock(EventFactory.class);
@@ -546,8 +546,9 @@ public void activateWithAttributes() throws Exception {
         when(mockBucketer.bucket(activatedExperiment, testBucketingId))
                 .thenReturn(bucketedVariation);
 
-        Map<String, String> attr = new HashMap<String,String>();
-        attr.put(attribute.getKey(), "attributeValue");
+        Map<String, String> attr = new HashMap<String, String>();
+
+        attr.put(attributeString.getKey(), "attributeValue");
         attr.put(testBucketingIdKey, testBucketingId);
 
         // activate the experiment
@@ -564,12 +565,77 @@ public void activateWithAttributes() throws Exception {
                 eq(bucketedVariation), eq(testUserId), attributeCaptor.capture());
 
         Map<String, String> actualValue = attributeCaptor.getValue();
-        assertThat(actualValue, hasEntry(attribute.getKey(), "attributeValue"));
+        assertThat(actualValue, hasEntry(attributeString.getKey(), "attributeValue"));
 
         // verify that dispatchEvent was called with the correct LogEvent object
         verify(mockEventHandler).dispatchEvent(logEventToDispatch);
     }
 
+    public void activateWithTypedAttributes() throws Exception {
+        if (datafileVersion < 4) {
+            return;
+        }
+
+        Experiment activatedExperiment = validProjectConfig.getExperiments().get(0);
+        Variation bucketedVariation = activatedExperiment.getVariations().get(0);
+        Variation userIdBucketedVariation = activatedExperiment.getVariations().get(1);
+        Attribute attributeString = validProjectConfig.getAttributes().get(0); 
+        Attribute attributeBoolean = validProjectConfig.getAttributes().get(3); 
+        Attribute attributeInteger = validProjectConfig.getAttributes().get(4); 
+        Attribute attributeDouble = validProjectConfig.getAttributes().get(5); 
+        
+        // setup a mock event builder to return expected impression params
+        EventFactory mockEventFactory = mock(EventFactory.class);
+
+        Optimizely optimizely = Optimizely.builder(validDatafile, mockEventHandler)
+                .withBucketing(mockBucketer)
+                .withEventBuilder(mockEventFactory)
+                .withConfig(validProjectConfig)
+                .withErrorHandler(mockErrorHandler)
+                .build();
+
+        when(mockEventFactory.createImpressionEvent(eq(validProjectConfig), eq(activatedExperiment), eq(bucketedVariation),
+                eq(testUserId), anyMapOf(String.class, Object.class)))
+                .thenReturn(logEventToDispatch);
+
+        when(mockBucketer.bucket(activatedExperiment, testUserId))
+                .thenReturn(userIdBucketedVariation);
+
+        when(mockBucketer.bucket(activatedExperiment, testBucketingId))
+                .thenReturn(bucketedVariation);
+
+        Map<String, Object> attr = new HashMap<>();
+
+        attr.put(attributeString.getKey(), "attributeValue");
+        attr.put(attributeBoolean.getKey(), true);
+        attr.put(attributeInteger.getKey(), 3);
+        attr.put(attributeDouble.getKey(), 3.123);
+        attr.put(testBucketingIdKey, testBucketingId);
+
+        // activate the experiment
+        Variation actualVariation = optimizely.activate(activatedExperiment.getKey(), testUserId,
+                attr);
+
+        // verify that the bucketing algorithm was called correctly
+        verify(mockBucketer).bucket(activatedExperiment, testBucketingId);
+        assertThat(actualVariation, is(bucketedVariation));
+
+        // setup the attribute map captor (so we can verify its content)
+        ArgumentCaptor<Map> attributeCaptor = ArgumentCaptor.forClass(Map.class);
+        verify(mockEventFactory).createImpressionEvent(eq(validProjectConfig), eq(activatedExperiment),
+                eq(bucketedVariation), eq(testUserId), attributeCaptor.capture());
+
+        Map<String, ?> actualValue = attributeCaptor.getValue();
+
+        assertThat((Map<String,? extends String>)actualValue, hasEntry(attributeString.getKey(), "attributeValue"));
+        assertThat((Map<String,? extends Boolean>)actualValue, hasEntry(attributeBoolean.getKey(), true));
+        assertThat((Map<String,? extends Integer>)actualValue, hasEntry(attributeInteger.getKey(), 3));
+        assertThat((Map<String,? extends Double>)actualValue, hasEntry(attributeDouble.getKey(), 3.123));
+
+        // verify that dispatchEvent was called with the correct LogEvent object
+        verify(mockEventHandler).dispatchEvent(logEventToDispatch);   
+    }
+
     /**
      * Verify that {@link Optimizely#activate(String, String, Map<String, String>)} handles the case
      * where an unknown attribute (i.e., not in the config) is passed through.
@@ -2322,11 +2388,11 @@ public void activateWithListener() throws Exception {
 
         ActivateNotificationListener activateNotification = new ActivateNotificationListener() {
             @Override
-            public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, String> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
+            public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, ?> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
                 assertEquals(experiment.getKey(), activatedExperiment.getKey());
                 assertEquals(bucketedVariation.getKey(), variation.getKey());
                 assertEquals(userId, testUserId);
-                for (Map.Entry<String, String> entry : attributes.entrySet()) {
+                for (Map.Entry<String, ?> entry : attributes.entrySet()) {
                     assertEquals(testUserAttributes.get(entry.getKey()), entry.getValue());
                 }
 
@@ -2384,7 +2450,7 @@ public void activateWithListenerNullAttributes() throws Exception {
 
         ActivateNotificationListener activateNotification = new ActivateNotificationListener() {
             @Override
-            public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, String> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
+            public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, ?> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
                 assertEquals(experiment.getKey(), activatedExperiment.getKey());
                 assertEquals(bucketedVariation.getKey(), variation.getKey());
                 assertEquals(userId, testUserId);
@@ -2719,7 +2785,7 @@ public void trackEventWithListenerAttributes() throws Exception {
 
         TrackNotificationListener trackNotification = new TrackNotificationListener() {
             @Override
-            public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull Map<String, String> _attributes, @Nonnull Map<String, ?> eventTags, @Nonnull LogEvent event) {
+            public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull Map<String, ?> _attributes, @Nonnull Map<String, ?> eventTags, @Nonnull LogEvent event) {
                 assertEquals(eventType.getKey(), eventKey);
                 assertEquals(genericUserId, userId);
                 assertEquals(attributes, _attributes);
@@ -2803,7 +2869,7 @@ public void trackEventWithListenerNullAttributes() throws Exception {
 
         TrackNotificationListener trackNotification = new TrackNotificationListener() {
             @Override
-            public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull Map<String, String> attributes, @Nonnull Map<String, ?> eventTags, @Nonnull LogEvent event) {
+            public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull Map<String, ?> attributes, @Nonnull Map<String, ?> eventTags, @Nonnull LogEvent event) {
                 assertEquals(eventType.getKey(), eventKey);
                 assertEquals(genericUserId, userId);
                 assertTrue(attributes.isEmpty());
diff --git a/core-api/src/test/java/com/optimizely/ab/config/ValidProjectConfigV4.java b/core-api/src/test/java/com/optimizely/ab/config/ValidProjectConfigV4.java
index 19a65dcba..19b3a4ae1 100644
--- a/core-api/src/test/java/com/optimizely/ab/config/ValidProjectConfigV4.java
+++ b/core-api/src/test/java/com/optimizely/ab/config/ValidProjectConfigV4.java
@@ -49,6 +49,18 @@ public class ValidProjectConfigV4 {
     public  static final String     ATTRIBUTE_OPT_KEY = "$opt_test";
     private static final Attribute  ATTRIBUTE_OPT = new Attribute(ATTRIBUTE_OPT_ID, ATTRIBUTE_OPT_KEY);
 
+    private static final String     ATTRIBUTE_BOOLEAN_ID = "323434545";
+    public  static final String     ATTRIBUTE_BOOLEAN_KEY = "booleanKey";
+    private static final Attribute  ATTRIBUTE_BOOLEAN = new Attribute(ATTRIBUTE_BOOLEAN_ID, ATTRIBUTE_BOOLEAN_KEY);
+
+    private static final String     ATTRIBUTE_INTEGER_ID = "616727838";
+    public  static final String     ATTRIBUTE_INTEGER_KEY = "integerKey";
+    private static final Attribute  ATTRIBUTE_INTEGER = new Attribute(ATTRIBUTE_INTEGER_ID, ATTRIBUTE_INTEGER_KEY);
+
+    private static final String     ATTRIBUTE_DOUBLE_ID = "808797686";
+    public  static final String     ATTRIBUTE_DOUBLE_KEY = "doubleKey";
+    private static final Attribute  ATTRIBUTE_DOUBLE = new Attribute(ATTRIBUTE_DOUBLE_ID, ATTRIBUTE_DOUBLE_KEY);
+
     // audiences
     private static final String     CUSTOM_DIMENSION_TYPE = "custom_dimension";
     private static final String     AUDIENCE_GRYFFINDOR_ID = "3468206642";
@@ -1033,6 +1045,9 @@ public static ProjectConfig generateValidProjectConfigV4() {
         attributes.add(ATTRIBUTE_HOUSE);
         attributes.add(ATTRIBUTE_NATIONALITY);
         attributes.add(ATTRIBUTE_OPT);
+        attributes.add(ATTRIBUTE_BOOLEAN);
+        attributes.add(ATTRIBUTE_INTEGER);
+        attributes.add(ATTRIBUTE_DOUBLE);
 
         // list audiences
         List<Audience> audiences = new ArrayList<Audience>();
diff --git a/core-api/src/test/java/com/optimizely/ab/config/audience/AudienceConditionEvaluationTest.java b/core-api/src/test/java/com/optimizely/ab/config/audience/AudienceConditionEvaluationTest.java
index d15bd70aa..74d4024e3 100644
--- a/core-api/src/test/java/com/optimizely/ab/config/audience/AudienceConditionEvaluationTest.java
+++ b/core-api/src/test/java/com/optimizely/ab/config/audience/AudienceConditionEvaluationTest.java
@@ -43,12 +43,19 @@
 public class AudienceConditionEvaluationTest {
 
     Map<String, String> testUserAttributes;
+    Map<String, Object> testTypedUserAttributes;
 
     @Before
     public void initialize() {
         testUserAttributes = new HashMap<String, String>();
         testUserAttributes.put("browser_type", "chrome");
         testUserAttributes.put("device_type", "Android");
+
+        testTypedUserAttributes = new HashMap<String, Object>();
+        testTypedUserAttributes.put("is_firefox", true);
+        testTypedUserAttributes.put("num_counts", 3.55);
+        testTypedUserAttributes.put("num_size", 3);
+        testTypedUserAttributes.put("meta_data", testUserAttributes);
     }
 
     /**
@@ -60,6 +67,23 @@ public void userAttributeEvaluateTrue() throws Exception {
         assertTrue(testInstance.evaluate(testUserAttributes));
     }
 
+
+    /**
+     * Verify that UserAttribute.evaluate returns true on exact-matching visitor attribute data.
+     */
+    @Test
+    public void typedUserAttributeEvaluateTrue() throws Exception {
+        UserAttribute testInstance = new UserAttribute("meta_data", "custom_dimension", testUserAttributes);
+        UserAttribute testInstance2 = new UserAttribute("is_firefox", "custom_dimension", true);
+        UserAttribute testInstance3 = new UserAttribute("num_counts", "custom_dimension", 3.55);
+        UserAttribute testInstance4 = new UserAttribute("num_size", "custom_dimension", 3);
+
+        assertTrue(testInstance.evaluate(testTypedUserAttributes));
+        assertTrue(testInstance2.evaluate(testTypedUserAttributes));
+        assertTrue(testInstance3.evaluate(testTypedUserAttributes));
+        assertTrue(testInstance4.evaluate(testTypedUserAttributes));
+    }
+
     /**
      * Verify that UserAttribute.evaluate returns false on non-exact-matching visitor attribute data.
      */
diff --git a/core-api/src/test/java/com/optimizely/ab/notification/NotificationCenterTest.java b/core-api/src/test/java/com/optimizely/ab/notification/NotificationCenterTest.java
index 08958be64..cffa01094 100644
--- a/core-api/src/test/java/com/optimizely/ab/notification/NotificationCenterTest.java
+++ b/core-api/src/test/java/com/optimizely/ab/notification/NotificationCenterTest.java
@@ -54,7 +54,7 @@ public void testAddWrongActivateNotificationListener() {
     public void testAddActivateNotificationTwice() {
         ActivateNotificationListener listener = new ActivateNotificationListener() {
             @Override
-            public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, String> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
+            public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, ?> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
 
             }
         };
@@ -70,7 +70,7 @@ public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @
     public void testAddActivateNotification() {
         int notificationId = notificationCenter.addActivateNotificationListener(new ActivateNotificationListenerInterface() {
             @Override
-            public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, String> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
+            public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, ?> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
 
             }
         });
@@ -83,7 +83,7 @@ public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @
     public void testAddTrackNotification() {
         int notificationId = notificationCenter.addTrackNotificationListener(new TrackNotificationListenerInterface() {
             @Override
-            public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull Map<String, String> attributes, @Nonnull Map<String, ?> eventTags, @Nonnull LogEvent event) {
+            public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull Map<String, ?> attributes, @Nonnull Map<String, ?> eventTags, @Nonnull LogEvent event) {
 
             }
         });
@@ -103,7 +103,7 @@ public void testNotificationTypeClasses() {
     public void testAddTrackNotificationInterface() {
         int notificationId = notificationCenter.addTrackNotificationListener(new TrackNotificationListenerInterface() {
             @Override
-            public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull Map<String, String> attributes, @Nonnull Map<String, ?> eventTags, @Nonnull LogEvent event) {
+            public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull Map<String, ?> attributes, @Nonnull Map<String, ?> eventTags, @Nonnull LogEvent event) {
 
             }
         });
@@ -116,7 +116,7 @@ public void onTrack(@Nonnull String eventKey, @Nonnull String userId, @Nonnull M
     public void testAddActivateNotificationInterface() {
         int notificationId = notificationCenter.addActivateNotificationListener(new ActivateNotificationListenerInterface() {
             @Override
-            public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, String> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
+            public void onActivate(@Nonnull Experiment experiment, @Nonnull String userId, @Nonnull Map<String, ?> attributes, @Nonnull Variation variation, @Nonnull LogEvent event) {
 
             }
         });
diff --git a/core-api/src/test/resources/config/valid-project-config-v4.json b/core-api/src/test/resources/config/valid-project-config-v4.json
index db961012e..e2feb6e91 100644
--- a/core-api/src/test/resources/config/valid-project-config-v4.json
+++ b/core-api/src/test/resources/config/valid-project-config-v4.json
@@ -39,6 +39,18 @@
     {
       "id": "583394100",
       "key": "$opt_test"
+    },
+    {
+      "id": "323434545",
+      "key": "booleanKey"
+    },
+    {
+      "id": "616727838",
+      "key": "integerKey"
+    },
+    {
+      "id": "808797686",
+      "key": "doubleKey"
     }
   ],
   "events": [