[Major] Total refactoring of StrolchElementVisitor hierarchy

li.strolch.agent/src/main/java/li/strolch/agent/impl/AuditingActivityMap.java

@@ -53,7 +53,7 @@ public class AuditingActivityMap extends AuditingElementMapFacade<Activity> impl
 		DBC.PRE.assertNotNull("activityVisitor on query", activityVisitor);
 		query.setActivityVisitor(activity -> {
 			this.read.add(activity);
-			return activityVisitor.visit(activity);
+			return activity.accept(activityVisitor);
 		});
 
 		return getElementMap().doQuery(tx, query);

li.strolch.agent/src/main/java/li/strolch/agent/impl/AuditingOrderMap.java

@@ -53,7 +53,7 @@ public class AuditingOrderMap extends AuditingElementMapFacade<Order> implements
 		DBC.PRE.assertNotNull("orderVisitor on query", orderVisitor);
 		query.setOrderVisitor(order -> {
 			this.read.add(order);
-			return orderVisitor.visit(order);
+			return order.accept(orderVisitor);
 		});
 
 		return getElementMap().doQuery(tx, query);

li.strolch.agent/src/main/java/li/strolch/agent/impl/AuditingResourceMap.java

@@ -22,7 +22,7 @@ import li.strolch.agent.api.ElementMap;
 import li.strolch.agent.api.ResourceMap;
 import li.strolch.model.Resource;
 import li.strolch.model.query.ResourceQuery;
-import li.strolch.model.visitor.ResourceVisitor;
+import li.strolch.model.visitor.StrolchElementVisitor;
 import li.strolch.persistence.api.StrolchTransaction;
 import li.strolch.utils.dbc.DBC;
 
@@ -49,11 +49,11 @@ public class AuditingResourceMap extends AuditingElementMapFacade<Resource> impl
 
 	@Override
 	public <U> List<U> doQuery(StrolchTransaction tx, ResourceQuery<U> query) {
-		ResourceVisitor<U> resourceVisitor = query.getResourceVisitor();
+		StrolchElementVisitor<U> resourceVisitor = query.getResourceVisitor();
 		DBC.PRE.assertNotNull("resourceVisitor on query", resourceVisitor);
 		query.setResourceVisitor(resource -> {
 			this.read.add(resource);
-			return resourceVisitor.visit(resource);
+			return resource.accept(resourceVisitor);
 		});
 
 		return getElementMap().doQuery(tx, query);

li.strolch.agent/src/main/java/li/strolch/runtime/query/inmemory/InMemoryQuery.java

@@ -33,14 +33,14 @@ public class InMemoryQuery<T extends StrolchRootElement, U> {
 
 	private Navigator<T> navigator;
 	private Selector<T> selector;
-	private StrolchElementVisitor<T, U> elementVisitor;
+	private StrolchElementVisitor<U> elementVisitor;
 	private Comparator<T> comparator;
 
 	public InMemoryQuery() {
 		// empty constructor
 	}
 
-	public InMemoryQuery(Navigator<T> navigator, Selector<T> selector, StrolchElementVisitor<T, U> elementVisitor,
+	public InMemoryQuery(Navigator<T> navigator, Selector<T> selector, StrolchElementVisitor<U> elementVisitor,
 			Comparator<T> comparator) {
 		this.navigator = navigator;
 		this.selector = selector;
@@ -68,7 +68,7 @@ public class InMemoryQuery<T extends StrolchRootElement, U> {
 	 * @param elementVisitor
 	 *            the elementVisitor to set
 	 */
-	public void setElementVisitor(StrolchElementVisitor<T, U> elementVisitor) {
+	public void setElementVisitor(StrolchElementVisitor<U> elementVisitor) {
 		this.elementVisitor = elementVisitor;
 	}
 
@@ -86,7 +86,7 @@ public class InMemoryQuery<T extends StrolchRootElement, U> {
 		while (iter.hasNext()) {
 			T element = iter.next();
 			if (this.selector.select(element)) {
-				U returnValue = this.elementVisitor.visit(element);
+				U returnValue = element.accept(this.elementVisitor);
 				DBC.INTERIM.assertNotNull("Visitor may not return null in query!", returnValue); //$NON-NLS-1$
 				result.add(returnValue);
 			}

li.strolch.model/src/main/java/li/strolch/model/AbstractStrolchRootElement.java

@@ -3,7 +3,6 @@ package li.strolch.model;
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 
-import li.strolch.model.json.StrolchElementToFlatJsonVisitor;
 import li.strolch.model.json.StrolchElementToJsonVisitor;
 import li.strolch.model.xml.StrolchElementToXmlStringVisitor;
 
@@ -21,7 +20,7 @@ public abstract class AbstractStrolchRootElement extends GroupedParameterizedEle
 
 	@Override
 	public String toXmlString() {
-		return this.accept(new StrolchElementToXmlStringVisitor());
+		return accept(new StrolchElementToXmlStringVisitor());
 	}
 
 	@Override
@@ -33,6 +32,6 @@ public abstract class AbstractStrolchRootElement extends GroupedParameterizedEle
 	@Override
 	public String toFlatJsonString() {
 		Gson gson = new GsonBuilder().setPrettyPrinting().create();
-		return gson.toJson(this.accept(new StrolchElementToFlatJsonVisitor()));
+		return gson.toJson(this.accept(new StrolchElementToJsonVisitor().flat()));
 	}
 }

li.strolch.model/src/main/java/li/strolch/model/Order.java

@@ -22,7 +22,7 @@ import li.strolch.exception.StrolchPolicyException;
 import li.strolch.model.Locator.LocatorBuilder;
 import li.strolch.model.policy.PolicyDef;
 import li.strolch.model.policy.PolicyDefs;
-import li.strolch.model.visitor.StrolchRootElementVisitor;
+import li.strolch.model.visitor.StrolchElementVisitor;
 import li.strolch.utils.iso8601.ISO8601FormatFactory;
 
 /**
@@ -188,7 +188,7 @@ public class Order extends AbstractStrolchRootElement implements StrolchRootElem
 	}
 
 	@Override
-	public <T> T accept(StrolchRootElementVisitor<T> visitor) {
+	public <T> T accept(StrolchElementVisitor<T> visitor) {
 		return visitor.visitOrder(this);
 	}
 

li.strolch.model/src/main/java/li/strolch/model/Resource.java

@@ -31,7 +31,7 @@ import li.strolch.model.policy.PolicyDef;
 import li.strolch.model.policy.PolicyDefs;
 import li.strolch.model.timedstate.StrolchTimedState;
 import li.strolch.model.timevalue.IValue;
-import li.strolch.model.visitor.StrolchRootElementVisitor;
+import li.strolch.model.visitor.StrolchElementVisitor;
 
 /**
  * @author Robert von Burg <eitch@eitchnet.ch>
@@ -208,7 +208,7 @@ public class Resource extends AbstractStrolchRootElement implements StrolchRootE
 	}
 
 	@Override
-	public <T> T accept(StrolchRootElementVisitor<T> visitor) {
+	public <T> T accept(StrolchElementVisitor<T> visitor) {
 		return visitor.visitResource(this);
 	}
 

li.strolch.model/src/main/java/li/strolch/model/StrolchRootElement.java

@@ -15,6 +15,7 @@
  */
 package li.strolch.model;
 
+import li.strolch.model.visitor.StrolchElementVisitor;
 import li.strolch.model.visitor.StrolchRootElementVisitor;
 
 /**
@@ -68,7 +69,7 @@ public interface StrolchRootElement extends StrolchElement, PolicyContainer, Par
 	 * 
 	 * @return the result of the visitation
 	 */
-	public <T> T accept(StrolchRootElementVisitor<T> visitor);
+	public <T> T accept(StrolchElementVisitor<T> visitor);
 
 	/**
 	 * Formats this {@link StrolchRootElement} as an XML string

li.strolch.model/src/main/java/li/strolch/model/activity/Action.java

@@ -310,6 +310,6 @@ public class Action extends GroupedParameterizedElement implements IActivityElem
 
 	@Override
 	public <T> T accept(IActivityElementVisitor<T> visitor) {
-		return visitor.visit(this);
+		return visitor.visitAction(this);
 	}
 }

li.strolch.model/src/main/java/li/strolch/model/activity/Activity.java

@@ -38,7 +38,7 @@ import li.strolch.model.parameter.Parameter;
 import li.strolch.model.policy.PolicyDef;
 import li.strolch.model.policy.PolicyDefs;
 import li.strolch.model.visitor.IActivityElementVisitor;
-import li.strolch.model.visitor.StrolchRootElementVisitor;
+import li.strolch.model.visitor.StrolchElementVisitor;
 import li.strolch.utils.dbc.DBC;
 
 /**
@@ -373,13 +373,13 @@ public class Activity extends AbstractStrolchRootElement
 	}
 
 	@Override
-	public <T> T accept(StrolchRootElementVisitor<T> visitor) {
+	public <T> T accept(StrolchElementVisitor<T> visitor) {
 		return visitor.visitActivity(this);
 	}
 
 	@Override
 	public <T> T accept(IActivityElementVisitor<T> visitor) {
-		return visitor.visit(this);
+		return visitor.visitActivity(this);
 	}
 
 	@Override

li.strolch.model/src/main/java/li/strolch/model/json/ActivityToFlatJsonVisitor.java

@@ -1,53 +0,0 @@
-package li.strolch.model.json;
-
-import java.util.function.BiConsumer;
-
-import com.google.gson.JsonObject;
-
-import li.strolch.model.Tags;
-import li.strolch.model.activity.Activity;
-import li.strolch.model.visitor.ActivityVisitor;
-
-public class ActivityToFlatJsonVisitor extends ToFlatJsonVisitor<Activity> implements ActivityVisitor<JsonObject> {
-
-	public ActivityToFlatJsonVisitor() {
-		super();
-	}
-
-	@Override
-	public ActivityToFlatJsonVisitor withVersion() {
-		super.withVersion();
-		return this;
-	}
-
-	@Override
-	public ActivityToFlatJsonVisitor withoutElementName() {
-		super.withoutElementName();
-		return this;
-	}
-
-	@Override
-	public ActivityToFlatJsonVisitor hook(BiConsumer<Activity, JsonObject> hook) {
-		super.hook(hook);
-		return this;
-	}
-
-	@Override
-	public ActivityToFlatJsonVisitor ignoreBag(String bagId) {
-		super.ignoreBag(bagId);
-		return this;
-	}
-
-	@Override
-	public ActivityToFlatJsonVisitor ignoreParameter(String bagId, String paramId) {
-		super.ignoreParameter(bagId, paramId);
-		return this;
-	}
-
-	@Override
-	public JsonObject visit(Activity element) {
-		JsonObject jsonObject = toJson(element);
-		jsonObject.addProperty(Tags.Json.STATE, element.getState().getName());
-		return jsonObject;
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/json/ActivityToJsonVisitor.java

@@ -1,29 +0,0 @@
-package li.strolch.model.json;
-
-import com.google.gson.Gson;
-import com.google.gson.JsonObject;
-
-import li.strolch.model.activity.Activity;
-import li.strolch.model.visitor.ActivityVisitor;
-
-public class ActivityToJsonVisitor extends StrolchElementToJsonVisitor implements ActivityVisitor<JsonObject> {
-
-	private JsonObject jsonObject;
-
-	public JsonObject getJsonObject() {
-		return this.jsonObject;
-	}
-
-	@Override
-	public JsonObject visit(Activity element) {
-		this.jsonObject = toJson(element);
-		return this.jsonObject;
-	}
-
-	public static String toJsonString(Activity element) {
-		ActivityToJsonVisitor visitor = new ActivityToJsonVisitor();
-		JsonObject jsonObject = visitor.visit(element);
-		String entity = new Gson().toJson(jsonObject);
-		return entity;
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/json/OrderToFlatJsonVisitor.java

@@ -1,57 +0,0 @@
-package li.strolch.model.json;
-
-import java.util.function.BiConsumer;
-
-import com.google.gson.JsonObject;
-
-import li.strolch.model.Order;
-import li.strolch.model.Tags;
-import li.strolch.model.visitor.OrderVisitor;
-import li.strolch.utils.iso8601.ISO8601FormatFactory;
-
-public class OrderToFlatJsonVisitor extends ToFlatJsonVisitor<Order> implements OrderVisitor<JsonObject> {
-
-	public OrderToFlatJsonVisitor() {
-		super();
-	}
-
-	@Override
-	public OrderToFlatJsonVisitor withVersion() {
-		super.withVersion();
-		return this;
-	}
-
-	@Override
-	public OrderToFlatJsonVisitor withoutElementName() {
-		super.withoutElementName();
-		return this;
-	}
-
-	@Override
-	public OrderToFlatJsonVisitor hook(BiConsumer<Order, JsonObject> hook) {
-		super.hook(hook);
-		return this;
-	}
-
-	@Override
-	public OrderToFlatJsonVisitor ignoreBag(String bagId) {
-		super.ignoreBag(bagId);
-		return this;
-	}
-
-	@Override
-	public OrderToFlatJsonVisitor ignoreParameter(String bagId, String paramId) {
-		super.ignoreParameter(bagId, paramId);
-		return this;
-	}
-
-	@Override
-	public JsonObject visit(Order element) {
-		JsonObject jsonObject = toJson(element);
-
-		jsonObject.addProperty(Tags.Json.DATE, ISO8601FormatFactory.getInstance().formatDate(element.getDate()));
-		jsonObject.addProperty(Tags.Json.STATE, element.getState().getName());
-
-		return jsonObject;
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/json/OrderToJsonVisitor.java

@@ -1,29 +0,0 @@
-package li.strolch.model.json;
-
-import com.google.gson.Gson;
-import com.google.gson.JsonObject;
-
-import li.strolch.model.Order;
-import li.strolch.model.visitor.OrderVisitor;
-
-public class OrderToJsonVisitor extends StrolchElementToJsonVisitor implements OrderVisitor<JsonObject> {
-
-	private JsonObject jsonObject;
-
-	public JsonObject getJsonObject() {
-		return this.jsonObject;
-	}
-
-	@Override
-	public JsonObject visit(Order element) {
-		this.jsonObject = toJson(element);
-		return this.jsonObject;
-	}
-
-	public static String toJsonString(Order element) {
-		OrderToJsonVisitor visitor = new OrderToJsonVisitor();
-		JsonObject jsonObject = visitor.visit(element);
-		String entity = new Gson().toJson(jsonObject);
-		return entity;
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/json/ResourceToFlatJsonVisitor.java

@@ -1,104 +0,0 @@
-package li.strolch.model.json;
-
-import java.util.HashSet;
-import java.util.Set;
-import java.util.function.BiConsumer;
-
-import com.google.gson.JsonArray;
-import com.google.gson.JsonObject;
-
-import li.strolch.exception.StrolchModelException;
-import li.strolch.model.Resource;
-import li.strolch.model.Tags;
-import li.strolch.model.timedstate.StrolchTimedState;
-import li.strolch.model.timevalue.ITimeValue;
-import li.strolch.model.timevalue.ITimeVariable;
-import li.strolch.model.timevalue.IValue;
-import li.strolch.model.visitor.ResourceVisitor;
-import li.strolch.utils.iso8601.ISO8601FormatFactory;
-
-public class ResourceToFlatJsonVisitor extends ToFlatJsonVisitor<Resource> implements ResourceVisitor<JsonObject> {
-
-	private Set<String> ignoredStates;
-	private boolean withoutTimedStates;
-
-	public ResourceToFlatJsonVisitor() {
-		super();
-		this.ignoredStates = new HashSet<>();
-	}
-
-	@Override
-	public ResourceToFlatJsonVisitor withVersion() {
-		super.withVersion();
-		return this;
-	}
-
-	public ResourceToFlatJsonVisitor withoutTimedStates() {
-		this.withoutTimedStates = true;
-		return this;
-	}
-
-	@Override
-	public ResourceToFlatJsonVisitor withoutElementName() {
-		super.withoutElementName();
-		return this;
-	}
-
-	@Override
-	public ResourceToFlatJsonVisitor hook(BiConsumer<Resource, JsonObject> hook) {
-		super.hook(hook);
-		return this;
-	}
-
-	@Override
-	public ResourceToFlatJsonVisitor ignoreBag(String bagId) {
-		super.ignoreBag(bagId);
-		return this;
-	}
-
-	@Override
-	public ResourceToFlatJsonVisitor ignoreParameter(String bagId, String paramId) {
-		super.ignoreParameter(bagId, paramId);
-		return this;
-	}
-
-	@Override
-	public JsonObject visit(Resource element) {
-		if (this.withoutTimedStates || !element.hasTimedStates())
-			return toJson(element);
-
-		JsonObject jsonObject = toJson(element);
-		addStates(element, jsonObject);
-		return jsonObject;
-	}
-
-	private void addStates(Resource element, JsonObject jsonObject) {
-		for (String stateKey : element.getTimedStateKeySet()) {
-
-			// see if we have to ignore this state
-			if (this.ignoredStates.contains(stateKey))
-				continue;
-
-			// get values
-			StrolchTimedState<IValue<?>> stateT = element.getTimedState(stateKey);
-			ITimeVariable<IValue<?>> timeEvolution = stateT.getTimeEvolution();
-
-			if (jsonObject.has(stateKey)) {
-				throw new StrolchModelException(
-						"JsonObject already has a member with ID " + stateKey + ": " + stateT.getLocator());
-			}
-
-			// build JSON data
-			JsonArray arrayJ = new JsonArray();
-			for (ITimeValue<IValue<?>> v : timeEvolution.getValues()) {
-				JsonObject obj = new JsonObject();
-				obj.addProperty(Tags.Json.DATE, ISO8601FormatFactory.getInstance().formatDate(v.getTime()));
-				obj.addProperty(Tags.Json.VALUE, v.getValue().getValueAsString());
-
-				arrayJ.add(obj);
-			}
-
-			jsonObject.add(stateKey, arrayJ);
-		}
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/json/ResourceToJsonVisitor.java

@@ -1,29 +0,0 @@
-package li.strolch.model.json;
-
-import com.google.gson.Gson;
-import com.google.gson.JsonObject;
-
-import li.strolch.model.Resource;
-import li.strolch.model.visitor.ResourceVisitor;
-
-public class ResourceToJsonVisitor extends StrolchElementToJsonVisitor implements ResourceVisitor<JsonObject> {
-
-	private JsonObject jsonObject;
-
-	public JsonObject getJsonObject() {
-		return this.jsonObject;
-	}
-
-	@Override
-	public JsonObject visit(Resource element) {
-		this.jsonObject = toJson(element);
-		return this.jsonObject;
-	}
-
-	public static String toJsonString(Resource element) {
-		ResourceToJsonVisitor visitor = new ResourceToJsonVisitor();
-		JsonObject jsonObject = visitor.visit(element);
-		String entity = new Gson().toJson(jsonObject);
-		return entity;
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/json/StrolchElementToFlatJsonVisitor.java

@@ -1,26 +0,0 @@
-package li.strolch.model.json;
-
-import com.google.gson.JsonObject;
-
-import li.strolch.model.Order;
-import li.strolch.model.Resource;
-import li.strolch.model.activity.Activity;
-import li.strolch.model.visitor.StrolchRootElementVisitor;
-
-public class StrolchElementToFlatJsonVisitor implements StrolchRootElementVisitor<JsonObject> {
-
-	@Override
-	public JsonObject visitOrder(Order order) {
-		return new OrderToFlatJsonVisitor().toJson(order);
-	}
-
-	@Override
-	public JsonObject visitResource(Resource resource) {
-		return new ResourceToFlatJsonVisitor().toJson(resource);
-	}
-
-	@Override
-	public JsonObject visitActivity(Activity activity) {
-		return new ActivityToFlatJsonVisitor().toJson(activity);
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/json/StrolchElementToJsonVisitor.java

@@ -1,13 +1,18 @@
 package li.strolch.model.json;
 
+import java.util.Collections;
 import java.util.Date;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Map.Entry;
+import java.util.Set;
 import java.util.SortedSet;
+import java.util.function.BiConsumer;
 
 import com.google.gson.JsonArray;
 import com.google.gson.JsonObject;
 
+import li.strolch.exception.StrolchModelException;
 import li.strolch.model.AbstractStrolchElement;
 import li.strolch.model.GroupedParameterizedElement;
 import li.strolch.model.Order;
@@ -16,6 +21,7 @@ import li.strolch.model.PolicyContainer;
 import li.strolch.model.Resource;
 import li.strolch.model.StrolchModelConstants;
 import li.strolch.model.StrolchRootElement;
+import li.strolch.model.StrolchValueType;
 import li.strolch.model.Tags;
 import li.strolch.model.Version;
 import li.strolch.model.activity.Action;
@@ -26,12 +32,100 @@ import li.strolch.model.policy.PolicyDef;
 import li.strolch.model.policy.PolicyDefs;
 import li.strolch.model.timedstate.StrolchTimedState;
 import li.strolch.model.timevalue.ITimeValue;
+import li.strolch.model.timevalue.ITimeVariable;
 import li.strolch.model.timevalue.IValue;
 import li.strolch.model.timevalue.IValueChange;
+import li.strolch.model.visitor.IActivityElementVisitor;
 import li.strolch.model.visitor.StrolchRootElementVisitor;
+import li.strolch.utils.collections.MapOfSets;
 import li.strolch.utils.iso8601.ISO8601FormatFactory;
 
-public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<JsonObject> {
+public class StrolchElementToJsonVisitor
+		implements StrolchRootElementVisitor<JsonObject>, IActivityElementVisitor<JsonObject> {
+
+	private MapOfSets<String, String> ignoredKeys;
+	private Set<String> ignoredStates;
+
+	private BiConsumer<Resource, JsonObject> resourceHook;
+	private BiConsumer<Order, JsonObject> orderHook;
+	private BiConsumer<Activity, JsonObject> activityHook;
+	private BiConsumer<Action, JsonObject> actionHook;
+
+	private boolean flat;
+	private boolean withoutElementName;
+	private boolean withVersion;
+	private boolean withoutPolicies;
+
+	public StrolchElementToJsonVisitor() {
+		this.ignoredKeys = new MapOfSets<>();
+		this.ignoredStates = new HashSet<>();
+	}
+
+	public boolean isFlat() {
+		return this.flat;
+	}
+
+	public boolean isWithVersion() {
+		return this.withVersion;
+	}
+
+	public boolean isWithoutElementName() {
+		return this.withoutElementName;
+	}
+
+	public boolean isWithoutPolicies() {
+		return this.withoutPolicies;
+	}
+
+	public StrolchElementToJsonVisitor withVersion() {
+		this.withVersion = true;
+		return this;
+	}
+
+	public StrolchElementToJsonVisitor withoutElementName() {
+		this.withoutElementName = true;
+		return this;
+	}
+
+	public StrolchElementToJsonVisitor withoutPolicies() {
+		this.withoutPolicies = true;
+		return this;
+	}
+
+	public StrolchElementToJsonVisitor flat() {
+		this.flat = true;
+		return this;
+	}
+
+	public StrolchElementToJsonVisitor ignoreBag(String bagId) {
+		this.ignoredKeys.addSet(bagId, Collections.emptySet());
+		return this;
+	}
+
+	public StrolchElementToJsonVisitor ignoreParameter(String bagId, String paramId) {
+		this.ignoredKeys.addElement(bagId, paramId);
+		return this;
+	}
+
+	public StrolchElementToJsonVisitor resourceHook(BiConsumer<Resource, JsonObject> hook) {
+		this.resourceHook = hook;
+		return this;
+	}
+
+	public StrolchElementToJsonVisitor orderHook(BiConsumer<Order, JsonObject> hook) {
+		this.orderHook = hook;
+		return this;
+	}
+
+	public StrolchElementToJsonVisitor activityHook(BiConsumer<Activity, JsonObject> hook) {
+		this.activityHook = hook;
+		return this;
+	}
+
+	public StrolchElementToJsonVisitor actionHook(BiConsumer<Action, JsonObject> hook) {
+		this.actionHook = hook;
+		return this;
+	}
 
 	@Override
 	public JsonObject visitResource(Resource resource) {
@@ -48,6 +142,11 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 		return toJson(activity);
 	}
 
+	@Override
+	public JsonObject visitAction(Action action) {
+		return toJson(action);
+	}
+
 	protected JsonObject toJson(Resource element) {
 
 		JsonObject rootJ = new JsonObject();
@@ -56,10 +155,13 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 		toJson(element, rootJ);
 
 		addVersion(element, rootJ);
-		addParameterBags(element, rootJ);
+		addParameters(element, rootJ);
-		addTimedStates(element, rootJ);
+		addStates(element, rootJ);
 		addPolicies(element, rootJ);
 
+		if (this.resourceHook != null)
+			this.resourceHook.accept(element, rootJ);
+
 		return rootJ;
 	}
 
@@ -73,15 +175,17 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 		rootJ.addProperty(Tags.Json.STATE, element.getState().getName());
 
 		addVersion(element, rootJ);
-		addParameterBags(element, rootJ);
+		addParameters(element, rootJ);
 		addPolicies(element, rootJ);
 
+		if (this.orderHook != null)
+			this.orderHook.accept(element, rootJ);
+
 		return rootJ;
 	}
 
 	protected JsonObject toJson(Activity element) {
 		JsonObject rootJ = new JsonObject();
-		addVersion(element, rootJ);
 		return toJson(element, rootJ);
 	}
 
@@ -94,16 +198,20 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 
 		rootJ.addProperty(Tags.Json.OBJECT_TYPE, Tags.Json.ACTIVITY);
 
+		toJson((AbstractStrolchElement) element, rootJ);
 		rootJ.addProperty(Tags.Json.TIME_ORDERING, element.getTimeOrdering().getName());
 		rootJ.addProperty(Tags.Json.STATE, element.getState().getName());
 		rootJ.addProperty(Tags.Json.START, formatDate(element.getStart()));
 		rootJ.addProperty(Tags.Json.END, formatDate(element.getEnd()));
 
-		toJson((AbstractStrolchElement) element, rootJ);
+		if (element.isRootElement())
-
+			addVersion(element, rootJ);
-		addParameterBags(element, rootJ);
+		addParameters(element, rootJ);
 		addPolicies(element, rootJ);
 
+		if (this.activityHook != null)
+			this.activityHook.accept(element, rootJ);
+
 		Iterator<Entry<String, IActivityElement>> iter = element.elementIterator();
 		if (iter.hasNext()) {
 
@@ -141,9 +249,12 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 		rootJ.addProperty(Tags.Json.START, formatDate(element.getStart()));
 		rootJ.addProperty(Tags.Json.END, formatDate(element.getEnd()));
 
-		addParameterBags(element, rootJ);
+		addParameters(element, rootJ);
 		addPolicies(element, rootJ);
 
+		if (this.actionHook != null)
+			this.actionHook.accept(element, rootJ);
+
 		// value changes
 		Iterator<IValueChange<? extends IValue<?>>> iter = element.getChanges().iterator();
 		if (iter.hasNext()) {
@@ -171,6 +282,8 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 	protected void addPolicies(PolicyContainer policyContainer, JsonObject rootJ) {
 		if (!policyContainer.hasPolicyDefs() || !policyContainer.getPolicyDefs().hasPolicyDefs())
 			return;
+		if (isWithoutPolicies())
+			return;
 
 		PolicyDefs policyDefs = policyContainer.getPolicyDefs();
 
@@ -186,13 +299,61 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 	protected JsonObject toJson(AbstractStrolchElement element, JsonObject rootJ) {
 
 		rootJ.addProperty(Tags.Json.ID, element.getId());
-		rootJ.addProperty(Tags.Json.NAME, element.getName());
+
+		if (!isWithoutElementName())
+			rootJ.addProperty(Tags.Json.NAME, element.getName());
+
 		rootJ.addProperty(Tags.Json.TYPE, element.getType());
 
 		return rootJ;
 	}
 
-	protected void addParameterBags(GroupedParameterizedElement element, JsonObject rootJ) {
+	protected void addParameters(GroupedParameterizedElement element, JsonObject rootJ) {
+		if (isFlat())
+			addParametersFlat(element, rootJ);
+		else
+			addParameterFull(element, rootJ);
+	}
+
+	protected void addParametersFlat(GroupedParameterizedElement element, JsonObject rootJ) {
+
+		Set<String> bagKeySet = element.getParameterBagKeySet();
+		for (String bagId : bagKeySet) {
+
+			// see if we have to ignore this bag i.e. empty set existing
+			Set<String> ignoredParamIds = this.ignoredKeys.getSet(bagId);
+			if (ignoredParamIds != null && ignoredParamIds.isEmpty())
+				continue;
+
+			ParameterBag parameterBag = element.getParameterBag(bagId);
+
+			Set<String> parameterKeySet = parameterBag.getParameterKeySet();
+			for (String paramId : parameterKeySet) {
+
+				// see if this parameter must be ignored
+				if (ignoredParamIds != null && ignoredParamIds.contains(paramId))
+					continue;
+
+				if (rootJ.has(paramId)) {
+					throw new StrolchModelException(
+							"JsonObject already has a member with ID " + paramId + ": " + parameterBag.getLocator());
+				}
+
+				Parameter<?> param = parameterBag.getParameter(paramId);
+
+				StrolchValueType type = StrolchValueType.parse(param.getType());
+				if (type.isBoolean()) {
+					rootJ.addProperty(paramId, (Boolean) param.getValue());
+				} else if (type.isNumber()) {
+					rootJ.addProperty(paramId, (Number) param.getValue());
+				} else {
+					rootJ.addProperty(paramId, param.getValueAsString());
+				}
+			}
+		}
+	}
+
+	protected void addParameterFull(GroupedParameterizedElement element, JsonObject rootJ) {
 
 		if (!element.hasParameterBags())
 			return;
@@ -239,7 +400,14 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 		}
 	}
 
-	protected void addTimedStates(Resource element, JsonObject rootJ) {
+	protected void addStates(Resource resource, JsonObject rootJ) {
+		if (isFlat())
+			addTimedStatesFlat(resource, rootJ);
+		else
+			addTimedStatesFull(resource, rootJ);
+	}
+
+	protected void addTimedStatesFull(Resource element, JsonObject rootJ) {
 
 		if (!element.hasTimedStates())
 			return;
@@ -248,6 +416,11 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 		rootJ.add(Tags.Json.TIMED_STATES, timedStatesJ);
 
 		for (String stateKey : element.getTimedStateKeySet()) {
+
+			// see if we have to ignore this state
+			if (this.ignoredStates.contains(stateKey))
+				continue;
+
 			StrolchTimedState<IValue<?>> state = element.getTimedState(stateKey);
 
 			JsonObject stateJ = new JsonObject();
@@ -273,9 +446,45 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 		}
 	}
 
-	public static void addVersion(StrolchRootElement element, JsonObject rootJ) {
+	private void addTimedStatesFlat(Resource element, JsonObject jsonObject) {
+
+		if (!element.hasTimedStates())
+			return;
+
+		for (String stateKey : element.getTimedStateKeySet()) {
+
+			// see if we have to ignore this state
+			if (this.ignoredStates.contains(stateKey))
+				continue;
+
+			// get values
+			StrolchTimedState<IValue<?>> stateT = element.getTimedState(stateKey);
+			ITimeVariable<IValue<?>> timeEvolution = stateT.getTimeEvolution();
+
+			if (jsonObject.has(stateKey)) {
+				throw new StrolchModelException(
+						"JsonObject already has a member with ID " + stateKey + ": " + stateT.getLocator());
+			}
+
+			// build JSON data
+			JsonArray arrayJ = new JsonArray();
+			for (ITimeValue<IValue<?>> v : timeEvolution.getValues()) {
+				JsonObject obj = new JsonObject();
+				obj.addProperty(Tags.Json.DATE, ISO8601FormatFactory.getInstance().formatDate(v.getTime()));
+				obj.addProperty(Tags.Json.VALUE, v.getValue().getValueAsString());
+
+				arrayJ.add(obj);
+			}
+
+			jsonObject.add(stateKey, arrayJ);
+		}
+	}
+
+	protected void addVersion(StrolchRootElement element, JsonObject rootJ) {
 		if (!element.hasVersion())
 			return;
+		if (!isWithVersion())
+			return;
 
 		Version version = element.getVersion();
 
@@ -286,7 +495,6 @@ public class StrolchElementToJsonVisitor implements StrolchRootElementVisitor<Js
 		versionJ.addProperty(Tags.Json.DELETED, version.isDeleted());
 		rootJ.add(Tags.Json.VERSION, versionJ);
 	}
-	
 
 	private static String formatDate(Date date) {
 		return ISO8601FormatFactory.getInstance().formatDate(date);

li.strolch.model/src/main/java/li/strolch/model/json/ToFlatJsonVisitor.java

@@ -1,142 +0,0 @@
-package li.strolch.model.json;
-
-import static li.strolch.model.Tags.Json.ID;
-import static li.strolch.model.Tags.Json.NAME;
-import static li.strolch.model.Tags.Json.OBJECT_TYPE;
-import static li.strolch.model.Tags.Json.TYPE;
-import static li.strolch.model.json.StrolchElementToJsonVisitor.addVersion;
-
-import java.util.Collections;
-import java.util.Set;
-import java.util.function.BiConsumer;
-
-import com.google.gson.JsonObject;
-
-import li.strolch.exception.StrolchModelException;
-import li.strolch.model.ParameterBag;
-import li.strolch.model.StrolchRootElement;
-import li.strolch.model.StrolchValueType;
-import li.strolch.model.parameter.Parameter;
-import li.strolch.utils.collections.MapOfSets;
-
-/**
- * <p>
- * Maps a given {@link StrolchRootElement} to a {@link JsonObject}. All {@link Parameter Parameters} are mapped to a
- * member of the {@link JsonObject}, {@link ParameterBag ParameterBags} are thus removed
- * </p>
- * 
- * <p>
- * To ignore {@link Parameter Parameters} or {@link ParameterBag ParameterBags} use the
- * {@link #ignoreParameter(String, String)} and {@link #ignoreBag(String)} methods
- * </p>
- * 
- * <p>
- * The mapping can be extended by setting hook:
- * </p>
- * 
- * <pre>
- * visitor.setHook((element, jsonObject) -> {
- * 	// do work
- * });
- * </pre>
- * 
- * @author Robert von Burg <eitch@eitchnet.ch>
- */
-public class ToFlatJsonVisitor<T extends StrolchRootElement> {
-
-	private MapOfSets<String, String> ignoredKeys;
-	private BiConsumer<T, JsonObject> hook;
-	private boolean withoutElementName;
-	private boolean withVersion;
-
-	public ToFlatJsonVisitor() {
-		this.ignoredKeys = new MapOfSets<>();
-	}
-	
-	public boolean isWithVersion() {
-		return this.withVersion;
-	}
-	
-	public boolean isWithoutElementName() {
-		return this.withoutElementName;
-	}
-
-	public ToFlatJsonVisitor<T> withVersion() {
-		this.withVersion = true;
-		return this;
-	}
-
-	public ToFlatJsonVisitor<T> withoutElementName() {
-		this.withoutElementName = true;
-		return this;
-	}
-
-	public ToFlatJsonVisitor<T> hook(BiConsumer<T, JsonObject> hook) {
-		this.hook = hook;
-		return this;
-	}
-
-	public ToFlatJsonVisitor<T> ignoreBag(String bagId) {
-		this.ignoredKeys.addSet(bagId, Collections.emptySet());
-		return this;
-	}
-
-	public ToFlatJsonVisitor<T> ignoreParameter(String bagId, String paramId) {
-		this.ignoredKeys.addElement(bagId, paramId);
-		return this;
-	}
-
-	protected JsonObject toJson(T element) {
-
-		JsonObject jsonObject = new JsonObject();
-
-		jsonObject.addProperty(ID, element.getId());
-		if (!this.withoutElementName)
-			jsonObject.addProperty(NAME, element.getName());
-		jsonObject.addProperty(TYPE, element.getType());
-		jsonObject.addProperty(OBJECT_TYPE, element.getClass().getSimpleName());
-
-		Set<String> bagKeySet = element.getParameterBagKeySet();
-		for (String bagId : bagKeySet) {
-
-			// see if we have to ignore this bag i.e. empty set existing
-			Set<String> ignoredParamIds = this.ignoredKeys.getSet(bagId);
-			if (ignoredParamIds != null && ignoredParamIds.isEmpty())
-				continue;
-
-			ParameterBag parameterBag = element.getParameterBag(bagId);
-
-			Set<String> parameterKeySet = parameterBag.getParameterKeySet();
-			for (String paramId : parameterKeySet) {
-
-				// see if this parameter must be ignored
-				if (ignoredParamIds != null && ignoredParamIds.contains(paramId))
-					continue;
-
-				if (jsonObject.has(paramId)) {
-					throw new StrolchModelException(
-							"JsonObject already has a member with ID " + paramId + ": " + parameterBag.getLocator());
-				}
-
-				Parameter<?> param = parameterBag.getParameter(paramId);
-
-				StrolchValueType type = StrolchValueType.parse(param.getType());
-				if (type.isBoolean()) {
-					jsonObject.addProperty(paramId, (Boolean) param.getValue());
-				} else if (type.isNumber()) {
-					jsonObject.addProperty(paramId, (Number) param.getValue());
-				} else {
-					jsonObject.addProperty(paramId, param.getValueAsString());
-				}
-			}
-		}
-
-		if (this.hook != null)
-			this.hook.accept(element, jsonObject);
-
-		if (this.withVersion)
-			addVersion(element, jsonObject);
-
-		return jsonObject;
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/query/ActivityQuery.java

@@ -19,6 +19,7 @@ import li.strolch.model.activity.Action;
 import li.strolch.model.activity.Activity;
 import li.strolch.model.query.ordering.StrolchQueryOrdering;
 import li.strolch.model.visitor.ActivityVisitor;
+import li.strolch.model.visitor.StrolchElementVisitor;
 import li.strolch.utils.dbc.DBC;
 
 /**
@@ -73,6 +74,12 @@ public class ActivityQuery<U> extends StrolchElementQuery<ActivityQueryVisitor>
 		return this;
 	}
 
+	public ActivityQuery<U> setVisitor(StrolchElementVisitor<U> visitor) {
+		DBC.PRE.assertNotNull("visitor", visitor);
+		this.activityVisitor = visitor.asActivityVisitor();
+		return this;
+	}
+
 	public ActivityQuery<U> setActivityVisitor(ActivityVisitor<U> activityVisitor) {
 		DBC.PRE.assertNotNull("activityVisitor", activityVisitor);
 		this.activityVisitor = activityVisitor;

li.strolch.model/src/main/java/li/strolch/model/query/OrderQuery.java

@@ -19,6 +19,7 @@ import li.strolch.model.Order;
 import li.strolch.model.parameter.Parameter;
 import li.strolch.model.query.ordering.StrolchQueryOrdering;
 import li.strolch.model.visitor.OrderVisitor;
+import li.strolch.model.visitor.StrolchElementVisitor;
 import li.strolch.utils.dbc.DBC;
 
 /**
@@ -73,6 +74,12 @@ public class OrderQuery<U> extends StrolchElementQuery<OrderQueryVisitor> {
 		return this;
 	}
 
+	public OrderQuery<U> setVisitor(StrolchElementVisitor<U> visitor) {
+		DBC.PRE.assertNotNull("visitor", visitor);
+		this.orderVisitor = visitor.asOrderVisitor();
+		return this;
+	}
+
 	public OrderQuery<U> setOrderVisitor(OrderVisitor<U> orderVisitor) {
 		DBC.PRE.assertNotNull("orderVisitor", orderVisitor);
 		this.orderVisitor = orderVisitor;

li.strolch.model/src/main/java/li/strolch/model/query/ResourceQuery.java

@@ -19,6 +19,7 @@ import li.strolch.model.Resource;
 import li.strolch.model.parameter.Parameter;
 import li.strolch.model.query.ordering.StrolchQueryOrdering;
 import li.strolch.model.visitor.ResourceVisitor;
+import li.strolch.model.visitor.StrolchElementVisitor;
 import li.strolch.utils.dbc.DBC;
 
 /**
@@ -73,6 +74,12 @@ public class ResourceQuery<U> extends StrolchElementQuery<ResourceQueryVisitor>
 		return this;
 	}
 
+	public ResourceQuery<U> setVisitor(StrolchElementVisitor<U> visitor) {
+		DBC.PRE.assertNotNull("visitor", visitor);
+		this.resourceVisitor = visitor.asResourceVisitor();
+		return this;
+	}
+
 	public ResourceQuery<U> setResourceVisitor(ResourceVisitor<U> resourceVisitor) {
 		DBC.PRE.assertNotNull("resourceVisitor", resourceVisitor);
 		this.resourceVisitor = resourceVisitor;

li.strolch.model/src/main/java/li/strolch/model/visitor/ActivityDeepEqualsVisitor.java

@@ -1,40 +0,0 @@
-/*
- * Copyright 2013 Robert von Burg <eitch@eitchnet.ch>
- * 
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- * 
- *     http://www.apache.org/licenses/LICENSE-2.0
- * 
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package li.strolch.model.visitor;
-
-import java.util.List;
-
-import li.strolch.model.Locator;
-import li.strolch.model.activity.Activity;
-
-/**
- * @author Robert von Burg <eitch@eitchnet.ch>
- */
-public class ActivityDeepEqualsVisitor extends StrolchElementDeepEqualsVisitor implements
-		ActivityVisitor<List<Locator>> {
-
-	private Activity sourceActivity;
-
-	public ActivityDeepEqualsVisitor(Activity sourceActivity) {
-		this.sourceActivity = sourceActivity;
-	}
-
-	@Override
-	public List<Locator> visit(Activity dstActivity) {
-		deepEquals(this.sourceActivity, dstActivity);
-		return getMismatchedLocators();
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/visitor/ActivityVisitor.java

@@ -15,14 +15,28 @@
  */
 package li.strolch.model.visitor;
 
-import li.strolch.model.activity.Activity;
+import li.strolch.model.Order;
+import li.strolch.model.Resource;
+import li.strolch.model.activity.Action;
 
 /**
  * @author Robert von Burg <eitch@eitchnet.ch>
  * @param <U>
  */
-public interface ActivityVisitor<U> extends StrolchElementVisitor<Activity, U> {
+public interface ActivityVisitor<U> extends StrolchElementVisitor<U> {
 
 	@Override
-	public U visit(Activity element);
+	public default U visitAction(Action action) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + action.getClass());
+	}
+
+	@Override
+	public default U visitOrder(Order order) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + order.getClass());
+	}
+
+	@Override
+	public default U visitResource(Resource resource) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + resource.getClass());
+	}
 }

li.strolch.model/src/main/java/li/strolch/model/visitor/IActivityElementVisitor.java

@@ -1,11 +1,17 @@
 package li.strolch.model.visitor;
 
-import li.strolch.model.activity.Action;
+import li.strolch.model.Order;
-import li.strolch.model.activity.Activity;
+import li.strolch.model.Resource;
 
-public interface IActivityElementVisitor<T> {
+public interface IActivityElementVisitor<T> extends StrolchElementVisitor<T> {
 
-	public T visit(Activity activity);
+	@Override
+	public default T visitOrder(Order order) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + order.getClass());
+	}
 
-	public T visit(Action action);
+	@Override
+	public default T visitResource(Resource resource) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + resource.getClass());
+	}
 }

li.strolch.model/src/main/java/li/strolch/model/visitor/NoStrategyActivityVisitor.java

@@ -1,29 +0,0 @@
-/*
- * Copyright 2015 Robert von Burg <eitch@eitchnet.ch>
- * 
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- * 
- *     http://www.apache.org/licenses/LICENSE-2.0
- * 
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package li.strolch.model.visitor;
-
-import li.strolch.model.activity.Activity;
-
-/**
- * @author Robert von Burg <eitch@eitchnet.ch>
- */
-public class NoStrategyActivityVisitor implements ActivityVisitor<Activity> {
-
-	@Override
-	public Activity visit(Activity element) {
-		return element;
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/visitor/NoStrategyOrderVisitor.java

@@ -1,29 +0,0 @@
-/*
- * Copyright 2013 Robert von Burg <eitch@eitchnet.ch>
- * 
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- * 
- *     http://www.apache.org/licenses/LICENSE-2.0
- * 
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package li.strolch.model.visitor;
-
-import li.strolch.model.Order;
-
-/**
- * @author Robert von Burg <eitch@eitchnet.ch>
- */
-public class NoStrategyOrderVisitor implements OrderVisitor<Order> {
-
-	@Override
-	public Order visit(Order element) {
-		return element;
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/visitor/NoStrategyResourceVisitor.java

@@ -1,29 +0,0 @@
-/*
- * Copyright 2013 Robert von Burg <eitch@eitchnet.ch>
- * 
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- * 
- *     http://www.apache.org/licenses/LICENSE-2.0
- * 
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package li.strolch.model.visitor;
-
-import li.strolch.model.Resource;
-
-/**
- * @author Robert von Burg <eitch@eitchnet.ch>
- */
-public class NoStrategyResourceVisitor implements ResourceVisitor<Resource> {
-
-	@Override
-	public Resource visit(Resource element) {
-		return element;
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/visitor/NoStrategyVisitor.java

@@ -1,29 +0,0 @@
-/*
- * Copyright 2013 Robert von Burg <eitch@eitchnet.ch>
- * 
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- * 
- *     http://www.apache.org/licenses/LICENSE-2.0
- * 
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package li.strolch.model.visitor;
-
-import li.strolch.model.StrolchElement;
-
-/**
- * @author Robert von Burg <eitch@eitchnet.ch>
- */
-public class NoStrategyVisitor<T extends StrolchElement> implements StrolchElementVisitor<T, T> {
-
-	@Override
-	public T visit(T element) {
-		return element;
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/visitor/OrderDeepEqualsVisitor.java

@@ -1,39 +0,0 @@
-/*
- * Copyright 2013 Robert von Burg <eitch@eitchnet.ch>
- * 
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- * 
- *     http://www.apache.org/licenses/LICENSE-2.0
- * 
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package li.strolch.model.visitor;
-
-import java.util.List;
-
-import li.strolch.model.Locator;
-import li.strolch.model.Order;
-
-/**
- * @author Robert von Burg <eitch@eitchnet.ch>
- */
-public class OrderDeepEqualsVisitor extends StrolchElementDeepEqualsVisitor implements OrderVisitor<List<Locator>> {
-
-	private Order srcOrder;
-
-	public OrderDeepEqualsVisitor(Order srcOrder) {
-		this.srcOrder = srcOrder;
-	}
-
-	@Override
-	public List<Locator> visit(Order dstOrder) {
-		deepEquals(this.srcOrder, dstOrder);
-		return getMismatchedLocators();
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/visitor/OrderVisitor.java

@@ -15,13 +15,27 @@
  */
 package li.strolch.model.visitor;
 
-import li.strolch.model.Order;
+import li.strolch.model.Resource;
+import li.strolch.model.activity.Action;
+import li.strolch.model.activity.Activity;
 
 /**
  * @author Robert von Burg <eitch@eitchnet.ch>
  */
-public interface OrderVisitor<U> extends StrolchElementVisitor<Order, U> {
+public interface OrderVisitor<U> extends StrolchElementVisitor<U> {
 
 	@Override
-	public U visit(Order element);
+	public default U visitAction(Action action) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + action.getClass());
+	}
+
+	@Override
+	public default U visitActivity(Activity activity) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + activity.getClass());
+	}
+
+	@Override
+	public default U visitResource(Resource resource) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + resource.getClass());
+	}
 }

li.strolch.model/src/main/java/li/strolch/model/visitor/ResourceDeepEqualsVisitor.java

@@ -1,40 +0,0 @@
-/*
- * Copyright 2013 Robert von Burg <eitch@eitchnet.ch>
- * 
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- * 
- *     http://www.apache.org/licenses/LICENSE-2.0
- * 
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package li.strolch.model.visitor;
-
-import java.util.List;
-
-import li.strolch.model.Locator;
-import li.strolch.model.Resource;
-
-/**
- * @author Robert von Burg <eitch@eitchnet.ch>
- */
-public class ResourceDeepEqualsVisitor extends StrolchElementDeepEqualsVisitor implements
-		ResourceVisitor<List<Locator>> {
-
-	private Resource srcRes;
-
-	public ResourceDeepEqualsVisitor(Resource sourceRes) {
-		this.srcRes = sourceRes;
-	}
-
-	@Override
-	public List<Locator> visit(Resource dstRes) {
-		deepEquals(this.srcRes, dstRes);
-		return getMismatchedLocators();
-	}
-}

li.strolch.model/src/main/java/li/strolch/model/visitor/ResourceVisitor.java

@@ -15,14 +15,28 @@
  */
 package li.strolch.model.visitor;
 
-import li.strolch.model.Resource;
+import li.strolch.model.Order;
+import li.strolch.model.activity.Action;
+import li.strolch.model.activity.Activity;
 
 /**
  * @author Robert von Burg <eitch@eitchnet.ch>
  * @param <U>
  */
-public interface ResourceVisitor<U> extends StrolchElementVisitor<Resource, U> {
+public interface ResourceVisitor<U> extends StrolchElementVisitor<U> {
 
 	@Override
-	public U visit(Resource element);
+	public default U visitAction(Action action) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + action.getClass());
+	}
+
+	@Override
+	public default U visitActivity(Activity activity) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + activity.getClass());
+	}
+
+	@Override
+	public default U visitOrder(Order order) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + order.getClass());
+	}
 }

li.strolch.model/src/main/java/li/strolch/model/visitor/StrolchElementDeepEqualsVisitor.java

@@ -47,11 +47,13 @@ import li.strolch.utils.dbc.DBC;
  * 
  * @author Robert von Burg <eitch@eitchnet.ch>
  */
-public class StrolchElementDeepEqualsVisitor {
+public class StrolchElementDeepEqualsVisitor implements StrolchElementVisitor<List<Locator>> {
 
 	private List<Locator> mismatchedLocators;
+	private StrolchElement srcElement;
 
-	public StrolchElementDeepEqualsVisitor() {
+	public StrolchElementDeepEqualsVisitor(StrolchElement srcElement) {
+		this.srcElement = srcElement;
 		this.mismatchedLocators = new ArrayList<>();
 	}
 
@@ -335,20 +337,42 @@ public class StrolchElementDeepEqualsVisitor {
 	}
 
 	public static boolean isEqual(Order srcOrder, Order dstOrder) {
-		OrderDeepEqualsVisitor visitor = new OrderDeepEqualsVisitor(srcOrder);
+		return srcOrder.accept(new StrolchElementDeepEqualsVisitor(dstOrder)).isEmpty();
-		visitor.visit(dstOrder);
-		return visitor.isEqual();
 	}
 
 	public static boolean isEqual(Resource srcRes, Resource dstRes) {
-		ResourceDeepEqualsVisitor visitor = new ResourceDeepEqualsVisitor(srcRes);
+		return srcRes.accept(new StrolchElementDeepEqualsVisitor(dstRes)).isEmpty();
-		visitor.visit(dstRes);
-		return visitor.isEqual();
 	}
 
 	public static boolean isEqual(Activity srcAct, Activity dstAct) {
-		ActivityDeepEqualsVisitor visitor = new ActivityDeepEqualsVisitor(srcAct);
+		return srcAct.accept(new StrolchElementDeepEqualsVisitor(dstAct)).isEmpty();
-		visitor.visit(dstAct);
+	}
-		return visitor.isEqual();
+
+	@Override
+	public List<Locator> visitOrder(Order order) {
+		DBC.PRE.assertEquals("Can't compare apples with pairs =)", this.srcElement.getClass(), order.getClass());
+		deepEquals((Order) this.srcElement, order);
+		return getMismatchedLocators();
+	}
+
+	@Override
+	public List<Locator> visitResource(Resource resource) {
+		DBC.PRE.assertEquals("Can't compare apples with pairs =)", this.srcElement.getClass(), resource.getClass());
+		deepEquals((Resource) this.srcElement, resource);
+		return getMismatchedLocators();
+	}
+
+	@Override
+	public List<Locator> visitActivity(Activity activity) {
+		DBC.PRE.assertEquals("Can't compare apples with pairs =)", this.srcElement.getClass(), activity.getClass());
+		deepEquals((Activity) this.srcElement, activity);
+		return getMismatchedLocators();
+	}
+
+	@Override
+	public List<Locator> visitAction(Action action) {
+		DBC.PRE.assertEquals("Can't compare apples with pairs =)", this.srcElement.getClass(), action.getClass());
+		deepEquals((Action) this.srcElement, action);
+		return getMismatchedLocators();
 	}
 }

li.strolch.model/src/main/java/li/strolch/model/visitor/StrolchElementVisitor.java

@@ -15,12 +15,33 @@
  */
 package li.strolch.model.visitor;
 
-import li.strolch.model.StrolchElement;
+import li.strolch.model.Order;
+import li.strolch.model.Resource;
+import li.strolch.model.activity.Action;
+import li.strolch.model.activity.Activity;
 
 /**
  * @author Robert von Burg <eitch@eitchnet.ch>
  */
-public interface StrolchElementVisitor<T extends StrolchElement, U> extends StrolchVisitor {
+public interface StrolchElementVisitor<T> extends StrolchVisitor {
 
-	public U visit(T element);
+	public T visitOrder(Order order);
+
+	public T visitResource(Resource resource);
+
+	public T visitActivity(Activity activity);
+
+	public T visitAction(Action action);
+
+	public default ResourceVisitor<T> asResourceVisitor() {
+		return resource -> this.visitResource(resource);
+	}
+
+	public default OrderVisitor<T> asOrderVisitor() {
+		return order -> this.visitOrder(order);
+	}
+
+	public default ActivityVisitor<T> asActivityVisitor() {
+		return activity -> this.visitActivity(activity);
+	}
 }

li.strolch.model/src/main/java/li/strolch/model/visitor/StrolchRootElementVisitor.java

@@ -17,16 +17,22 @@ package li.strolch.model.visitor;
 
 import li.strolch.model.Order;
 import li.strolch.model.Resource;
+import li.strolch.model.activity.Action;
 import li.strolch.model.activity.Activity;
 
 /**
  * @author Robert von Burg <eitch@eitchnet.ch>
  */
-public interface StrolchRootElementVisitor<T> extends StrolchVisitor {
+public interface StrolchRootElementVisitor<T> extends StrolchElementVisitor<T> {
 
 	public T visitOrder(Order order);
 
 	public T visitResource(Resource resource);
 
 	public T visitActivity(Activity activity);
+
+	@Override
+	public default T visitAction(Action action) {
+		throw new UnsupportedOperationException(getClass().getName() + " can not handle " + action.getClass());
+	}
 }

li.strolch.model/src/test/java/li/strolch/model/ModelTest.java

@@ -96,9 +96,7 @@ import li.strolch.model.timevalue.IValueChange;
 import li.strolch.model.timevalue.impl.BooleanValue;
 import li.strolch.model.timevalue.impl.IntegerValue;
 import li.strolch.model.timevalue.impl.ValueChange;
-import li.strolch.model.visitor.ActivityDeepEqualsVisitor;
+import li.strolch.model.visitor.StrolchElementDeepEqualsVisitor;
-import li.strolch.model.visitor.OrderDeepEqualsVisitor;
-import li.strolch.model.visitor.ResourceDeepEqualsVisitor;
 
 @SuppressWarnings("nls")
 public class ModelTest {
@@ -242,18 +240,18 @@ public class ModelTest {
 	public void shouldPerformDeepActivityEquals() {
 		Activity srcActivity = createActivity("@act01", "Test Activity", "MyType", TimeOrdering.SERIES);
 		Activity dstActivity = createActivity("@act01", "Test Activity", "MyType", TimeOrdering.SERIES);
-		ActivityDeepEqualsVisitor visitor = new ActivityDeepEqualsVisitor(srcActivity);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcActivity);
-		visitor.visit(dstActivity);
+		List<Locator> mismatches = dstActivity.accept(visitor);
-		assertTrue("Same Activity should be deep equal!", visitor.isEqual());
+		assertTrue("Same Activity should be deep equal!", mismatches.isEmpty());
 	}
 
 	@Test
 	public void shouldPerformActivityClone() {
 		Activity srcActivity = createActivity("@act01", "Test Activity", "MyType", TimeOrdering.SERIES);
 		Activity dstActivity = srcActivity.getClone();
-		ActivityDeepEqualsVisitor visitor = new ActivityDeepEqualsVisitor(srcActivity);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcActivity);
-		visitor.visit(dstActivity);
+		List<Locator> mismatches = dstActivity.accept(visitor);
-		assertTrue("Cloned Activity should be deep equal: " + visitor.getMismatchedLocators(), visitor.isEqual());
+		assertTrue("Cloned Activity should be deep equal: " + mismatches, mismatches.isEmpty());
 	}
 
 	@Test
@@ -267,10 +265,10 @@ public class ModelTest {
 		FloatParameter fParam = bag.getParameter(PARAM_FLOAT_ID);
 		fParam.setValue(23434234.234);
 		fParam.setName("Ohla");
-		ActivityDeepEqualsVisitor visitor = new ActivityDeepEqualsVisitor(srcActivity);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcActivity);
-		visitor.visit(dstActivity);
+		List<Locator> mismatches = dstActivity.accept(visitor);
-		assertFalse("Activity should not be same if something has been changed", visitor.isEqual());
+		assertFalse("Activity should not be same if something has been changed", mismatches.isEmpty());
-		assertEquals("Multiple changes should be registered", 6, visitor.getMismatchedLocators().size());
+		assertEquals("Multiple changes should be registered", 6, mismatches.size());
 	}
 
 	@Test
@@ -297,28 +295,28 @@ public class ModelTest {
 		action = activity.getElement("action1_" + "@act01");
 		action.addChange(new ValueChange<>(1234567890L, new IntegerValue(12345), STATE_INTEGER_ID));
 
-		ActivityDeepEqualsVisitor visitor = new ActivityDeepEqualsVisitor(srcActivity);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcActivity);
-		visitor.visit(dstActivity);
+		List<Locator> mismatches = dstActivity.accept(visitor);
-		assertFalse("Activity should not be same if something has been changed", visitor.isEqual());
+		assertFalse("Activity should not be same if something has been changed", mismatches.isEmpty());
-		assertEquals("Multiple changes should be registered", 9, visitor.getMismatchedLocators().size());
+		assertEquals("Multiple changes should be registered", 9, mismatches.size());
 	}
 
 	@Test
 	public void shouldPerformDeepResourceEquals() {
 		Resource srcRes = createResource("@res01", "Test resource", "MyType");
 		Resource dstRes = createResource("@res01", "Test resource", "MyType");
-		ResourceDeepEqualsVisitor visitor = new ResourceDeepEqualsVisitor(srcRes);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcRes);
-		visitor.visit(dstRes);
+		List<Locator> mismatches = dstRes.accept(visitor);
-		assertTrue("Same Resource should be deep equal!", visitor.isEqual());
+		assertTrue("Same Resource should be deep equal!", mismatches.isEmpty());
 	}
 
 	@Test
 	public void shouldPerformResourceClone() {
 		Resource srcRes = createResource("@res01", "Test resource", "MyType");
 		Resource dstRes = srcRes.getClone();
-		ResourceDeepEqualsVisitor visitor = new ResourceDeepEqualsVisitor(srcRes);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcRes);
-		visitor.visit(dstRes);
+		List<Locator> mismatches = dstRes.accept(visitor);
-		assertTrue("Cloned Resource should be deep equal!", visitor.isEqual());
+		assertTrue("Cloned Resource should be deep equal!", mismatches.isEmpty());
 	}
 
 	@Test
@@ -330,10 +328,10 @@ public class ModelTest {
 		FloatParameter fParam = bag.getParameter(PARAM_FLOAT_ID);
 		fParam.setValue(23434234.234);
 		fParam.setName("Ohla");
-		ResourceDeepEqualsVisitor visitor = new ResourceDeepEqualsVisitor(srcRes);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcRes);
-		visitor.visit(dstRes);
+		List<Locator> mismatches = dstRes.accept(visitor);
-		assertFalse("Resource should not be same if param is changed!", visitor.isEqual());
+		assertFalse("Resource should not be same if param is changed!", mismatches.isEmpty());
-		assertEquals("Multiple changes should be registered", 3, visitor.getMismatchedLocators().size());
+		assertEquals("Multiple changes should be registered", 3, mismatches.size());
 	}
 
 	@Test
@@ -343,10 +341,10 @@ public class ModelTest {
 		BooleanTimedState timedState = dstRes.getTimedState(STATE_BOOLEAN_ID);
 		timedState.applyChange(new ValueChange<>(System.currentTimeMillis(), new BooleanValue(Boolean.FALSE)));
 		timedState.setName("Ohla");
-		ResourceDeepEqualsVisitor visitor = new ResourceDeepEqualsVisitor(srcRes);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcRes);
-		visitor.visit(dstRes);
+		List<Locator> mismatches = dstRes.accept(visitor);
 		assertFalse("Resource should not be same if param is changed!", visitor.isEqual());
-		assertEquals("Multiple change should be registered!", 2, visitor.getMismatchedLocators().size());
+		assertEquals("Multiple change should be registered!", 2, mismatches.size());
 	}
 
 	@Test
@@ -354,9 +352,9 @@ public class ModelTest {
 		Date date = new Date();
 		Order srcOrder = createOrder("@ord01", "Test Order", "MyType", date, State.CREATED);
 		Order dstOrder = createOrder("@ord01", "Test Order", "MyType", date, State.CREATED);
-		OrderDeepEqualsVisitor visitor = new OrderDeepEqualsVisitor(srcOrder);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcOrder);
-		visitor.visit(dstOrder);
+		List<Locator> mismatches = dstOrder.accept(visitor);
-		assertTrue("Same Order should be deep equal: " + visitor.getMismatchedLocators(), visitor.isEqual());
+		assertTrue("Same Order should be deep equal: " + mismatches, visitor.isEqual());
 	}
 
 	@Test
@@ -364,9 +362,9 @@ public class ModelTest {
 		Date date = new Date();
 		Order srcOrder = createOrder("@ord01", "Test Order", "MyType", date, State.CREATED);
 		Order dstOrder = srcOrder.getClone();
-		OrderDeepEqualsVisitor visitor = new OrderDeepEqualsVisitor(srcOrder);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcOrder);
-		visitor.visit(dstOrder);
+		List<Locator> mismatches = dstOrder.accept(visitor);
-		assertTrue("Cloned Order should be deep equal: " + visitor.getMismatchedLocators(), visitor.isEqual());
+		assertTrue("Cloned Order should be deep equal: " + mismatches, visitor.isEqual());
 	}
 
 	@Test
@@ -381,10 +379,10 @@ public class ModelTest {
 		FloatParameter fParam = bag.getParameter(PARAM_FLOAT_ID);
 		fParam.setValue(23434234.234);
 		fParam.setName("Ohla");
-		OrderDeepEqualsVisitor visitor = new OrderDeepEqualsVisitor(srcOrder);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(srcOrder);
-		visitor.visit(dstOrder);
+		List<Locator> mismatches = dstOrder.accept(visitor);
 		assertFalse("Order should not be same if something has been changed", visitor.isEqual());
-		assertEquals("Multiple changes should be registered", 5, visitor.getMismatchedLocators().size());
+		assertEquals("Multiple changes should be registered", 5, mismatches.size());
 	}
 
 	public static void validateBag(ParameterBag bag) {

li.strolch.model/src/test/java/li/strolch/model/ModelToDomTest.java

@@ -17,12 +17,12 @@ package li.strolch.model;
 
 import static org.junit.Assert.assertTrue;
 
+import java.util.List;
+
 import org.w3c.dom.Document;
 
 import li.strolch.model.activity.Activity;
-import li.strolch.model.visitor.ActivityDeepEqualsVisitor;
+import li.strolch.model.visitor.StrolchElementDeepEqualsVisitor;
-import li.strolch.model.visitor.OrderDeepEqualsVisitor;
-import li.strolch.model.visitor.ResourceDeepEqualsVisitor;
 import li.strolch.model.xml.ActivityFromDomVisitor;
 import li.strolch.model.xml.OrderFromDomVisitor;
 import li.strolch.model.xml.ResourceFromDomVisitor;
@@ -40,10 +40,9 @@ public class ModelToDomTest extends ModelMarshallingTest {
 
 		Resource parsedResource = new ResourceFromDomVisitor().visit(document);
 
-		ResourceDeepEqualsVisitor visitor = new ResourceDeepEqualsVisitor(resource);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(resource);
-		visitor.visit(parsedResource);
+		List<Locator> mismatches = parsedResource.accept(visitor);
-		assertTrue("To DOM and back should equal same Resource:\n" + visitor.getMismatchedLocators(),
+		assertTrue("To DOM and back should equal same Resource:\n" + mismatches, mismatches.isEmpty());
-				visitor.isEqual());
 
 		return parsedResource;
 	}
@@ -54,9 +53,9 @@ public class ModelToDomTest extends ModelMarshallingTest {
 
 		Order parsedOrder = new OrderFromDomVisitor().visit(document);
 
-		OrderDeepEqualsVisitor visitor = new OrderDeepEqualsVisitor(order);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(order);
-		visitor.visit(parsedOrder);
+		List<Locator> mismatches = parsedOrder.accept(visitor);
-		assertTrue("To DOM and back should equal same Order:\n" + visitor.getMismatchedLocators(), visitor.isEqual());
+		assertTrue("To DOM and back should equal same Order:\n" + mismatches, mismatches.isEmpty());
 
 		return parsedOrder;
 	}
@@ -67,10 +66,9 @@ public class ModelToDomTest extends ModelMarshallingTest {
 
 		Activity parsedActivity = new ActivityFromDomVisitor().visit(document);
 
-		ActivityDeepEqualsVisitor visitor = new ActivityDeepEqualsVisitor(activity);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(activity);
-		visitor.visit(parsedActivity);
+		List<Locator> mismatches = parsedActivity.accept(visitor);
-		assertTrue("To DOM and back should equal same Activity:\n" + visitor.getMismatchedLocators(),
+		assertTrue("To DOM and back should equal same Activity:\n" + mismatches, mismatches.isEmpty());
-				visitor.isEqual());
 
 		return parsedActivity;
 	}

li.strolch.model/src/test/java/li/strolch/model/ModelToJsonTest.java

@@ -17,32 +17,29 @@ package li.strolch.model;
 
 import static org.junit.Assert.assertTrue;
 
+import java.util.List;
+
 import com.google.gson.JsonObject;
 
 import li.strolch.model.activity.Activity;
 import li.strolch.model.json.ActivityFromJsonVisitor;
-import li.strolch.model.json.ActivityToJsonVisitor;
 import li.strolch.model.json.OrderFromJsonVisitor;
-import li.strolch.model.json.OrderToJsonVisitor;
 import li.strolch.model.json.ResourceFromJsonVisitor;
-import li.strolch.model.json.ResourceToJsonVisitor;
+import li.strolch.model.json.StrolchElementToJsonVisitor;
-import li.strolch.model.visitor.ActivityDeepEqualsVisitor;
+import li.strolch.model.visitor.StrolchElementDeepEqualsVisitor;
-import li.strolch.model.visitor.OrderDeepEqualsVisitor;
-import li.strolch.model.visitor.ResourceDeepEqualsVisitor;
 
 public class ModelToJsonTest extends ModelMarshallingTest {
 
 	@Override
 	protected Order formatAndParseOrder(Order order) {
-		OrderToJsonVisitor jsonVisitor = new OrderToJsonVisitor();
+		StrolchElementToJsonVisitor jsonVisitor = new StrolchElementToJsonVisitor().withVersion();
-		jsonVisitor.visit(order);
+		JsonObject jsonObject = order.accept(jsonVisitor);
-		JsonObject jsonObject = jsonVisitor.getJsonObject();
 
 		Order parsedOrder = new OrderFromJsonVisitor().visit(jsonObject);
 
-		OrderDeepEqualsVisitor visitor = new OrderDeepEqualsVisitor(order);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(order);
-		visitor.visit(parsedOrder);
+		List<Locator> mismatches = parsedOrder.accept(visitor);
-		assertTrue("To JSON and back should equal same Order:\n" + visitor.getMismatchedLocators(), visitor.isEqual());
+		assertTrue("To JSON and back should equal same Order:\n" + mismatches, mismatches.isEmpty());
 
 		return parsedOrder;
 	}
@@ -50,16 +47,14 @@ public class ModelToJsonTest extends ModelMarshallingTest {
 	@Override
 	protected Resource formatAndParseResource(Resource resource) {
 
-		ResourceToJsonVisitor jsonVisitor = new ResourceToJsonVisitor();
+		StrolchElementToJsonVisitor jsonVisitor = new StrolchElementToJsonVisitor().withVersion();
-		jsonVisitor.visit(resource);
+		JsonObject jsonObject = resource.accept(jsonVisitor);
-		JsonObject jsonObject = jsonVisitor.getJsonObject();
 
 		Resource parsedResource = new ResourceFromJsonVisitor().visit(jsonObject);
 
-		ResourceDeepEqualsVisitor visitor = new ResourceDeepEqualsVisitor(resource);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(resource);
-		visitor.visit(parsedResource);
+		List<Locator> mismatches = parsedResource.accept(visitor);
-		assertTrue("To JSON and back should equal same Resource:\n" + visitor.getMismatchedLocators(),
+		assertTrue("To JSON and back should equal same Resource:\n" + mismatches, mismatches.isEmpty());
-				visitor.isEqual());
 
 		return parsedResource;
 	}
@@ -67,16 +62,14 @@ public class ModelToJsonTest extends ModelMarshallingTest {
 	@Override
 	protected Activity formatAndParseActivity(Activity activity) {
 
-		ActivityToJsonVisitor jsonVisitor = new ActivityToJsonVisitor();
+		StrolchElementToJsonVisitor jsonVisitor = new StrolchElementToJsonVisitor().withVersion();
-		jsonVisitor.visit(activity);
+		JsonObject jsonObject = activity.accept(jsonVisitor);
-		JsonObject jsonObject = jsonVisitor.getJsonObject();
 
 		Activity parsedActivity = new ActivityFromJsonVisitor().visit(jsonObject);
 
-		ActivityDeepEqualsVisitor visitor = new ActivityDeepEqualsVisitor(activity);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(activity);
-		visitor.visit(parsedActivity);
+		List<Locator> mismatches = parsedActivity.accept(visitor);
-		assertTrue("To JSON and back should equal same Activity:\n" + visitor.getMismatchedLocators(),
+		assertTrue("To JSON and back should equal same Activity:\n" + mismatches, mismatches.isEmpty());
-				visitor.isEqual());
 
 		return parsedActivity;
 	}

li.strolch.model/src/test/java/li/strolch/model/ModelToSaxTest.java

@@ -19,11 +19,10 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
 import java.util.Collections;
+import java.util.List;
 
 import li.strolch.model.activity.Activity;
-import li.strolch.model.visitor.ActivityDeepEqualsVisitor;
+import li.strolch.model.visitor.StrolchElementDeepEqualsVisitor;
-import li.strolch.model.visitor.OrderDeepEqualsVisitor;
-import li.strolch.model.visitor.ResourceDeepEqualsVisitor;
 import li.strolch.model.xml.SimpleStrolchElementListener;
 import li.strolch.model.xml.StrolchElementToSaxVisitor;
 import li.strolch.model.xml.XmlModelSaxReader;
@@ -47,9 +46,9 @@ public class ModelToSaxTest extends ModelMarshallingTest {
 		assertEquals(Collections.emptyList(), listener.getActivities());
 		Order parsedOrder = listener.getOrders().get(0);
 
-		OrderDeepEqualsVisitor visitor = new OrderDeepEqualsVisitor(order);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(order);
-		visitor.visit(parsedOrder);
+		List<Locator> mismatches = parsedOrder.accept(visitor);
-		assertTrue("To DOM and back should equal same Order:\n" + visitor.getMismatchedLocators(), visitor.isEqual());
+		assertTrue("To DOM and back should equal same Order:\n" + mismatches, mismatches.isEmpty());
 
 		return parsedOrder;
 	}
@@ -67,10 +66,9 @@ public class ModelToSaxTest extends ModelMarshallingTest {
 		assertEquals(Collections.emptyList(), listener.getOrders());
 		Resource parsedResource = listener.getResources().get(0);
 
-		ResourceDeepEqualsVisitor visitor = new ResourceDeepEqualsVisitor(resource);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(resource);
-		visitor.visit(parsedResource);
+		List<Locator> mismatches = parsedResource.accept(visitor);
-		assertTrue("To DOM and back should equal same Resource:\n" + visitor.getMismatchedLocators(),
+		assertTrue("To DOM and back should equal same Resource:\n" + mismatches, mismatches.isEmpty());
-				visitor.isEqual());
 
 		return parsedResource;
 	}
@@ -88,10 +86,9 @@ public class ModelToSaxTest extends ModelMarshallingTest {
 		assertEquals(Collections.emptyList(), listener.getOrders());
 		Activity parsedActivity = listener.getActivities().get(0);
 
-		ActivityDeepEqualsVisitor visitor = new ActivityDeepEqualsVisitor(activity);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(activity);
-		visitor.visit(parsedActivity);
+		List<Locator> mismatches = parsedActivity.accept(visitor);
-		assertTrue("To DOM and back should equal same Activity:\n" + visitor.getMismatchedLocators(),
+		assertTrue("To DOM and back should equal same Activity:\n" + mismatches, mismatches.isEmpty());
-				visitor.isEqual());
 
 		return parsedActivity;
 	}

li.strolch.model/src/test/java/li/strolch/model/ModelToSaxWriterTest.java

@@ -21,13 +21,12 @@ import static org.junit.Assert.assertTrue;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.util.Collections;
+import java.util.List;
 
 import javax.xml.stream.XMLStreamWriter;
 
 import li.strolch.model.activity.Activity;
-import li.strolch.model.visitor.ActivityDeepEqualsVisitor;
+import li.strolch.model.visitor.StrolchElementDeepEqualsVisitor;
-import li.strolch.model.visitor.OrderDeepEqualsVisitor;
-import li.strolch.model.visitor.ResourceDeepEqualsVisitor;
 import li.strolch.model.xml.SimpleStrolchElementListener;
 import li.strolch.model.xml.StrolchElementToSaxWriterVisitor;
 import li.strolch.model.xml.StrolchXmlHelper;
@@ -57,9 +56,9 @@ public class ModelToSaxWriterTest extends ModelMarshallingTest {
 		assertEquals(Collections.emptyList(), listener.getActivities());
 		Order parsedOrder = listener.getOrders().get(0);
 
-		OrderDeepEqualsVisitor visitor = new OrderDeepEqualsVisitor(order);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(order);
-		visitor.visit(parsedOrder);
+		List<Locator> mismatches = parsedOrder.accept(visitor);
-		assertTrue("To DOM and back should equal same Order:\n" + visitor.getMismatchedLocators(), visitor.isEqual());
+		assertTrue("To DOM and back should equal same Order:\n" + mismatches, mismatches.isEmpty());
 
 		return parsedOrder;
 	}
@@ -82,10 +81,9 @@ public class ModelToSaxWriterTest extends ModelMarshallingTest {
 		assertEquals(Collections.emptyList(), listener.getOrders());
 		Resource parsedResource = listener.getResources().get(0);
 
-		ResourceDeepEqualsVisitor visitor = new ResourceDeepEqualsVisitor(resource);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(resource);
-		visitor.visit(parsedResource);
+		List<Locator> mismatches = parsedResource.accept(visitor);
-		assertTrue("To DOM and back should equal same Resource:\n" + visitor.getMismatchedLocators(),
+		assertTrue("To DOM and back should equal same Resource:\n" + mismatches, mismatches.isEmpty());
-				visitor.isEqual());
 
 		return parsedResource;
 	}
@@ -110,10 +108,9 @@ public class ModelToSaxWriterTest extends ModelMarshallingTest {
 		assertEquals(Collections.emptyList(), listener.getOrders());
 		Activity parsedActivity = listener.getActivities().get(0);
 
-		ActivityDeepEqualsVisitor visitor = new ActivityDeepEqualsVisitor(activity);
+		StrolchElementDeepEqualsVisitor visitor = new StrolchElementDeepEqualsVisitor(activity);
-		visitor.visit(parsedActivity);
+		List<Locator> mismatches = parsedActivity.accept(visitor);
-		assertTrue("To DOM and back should equal same Activity:\n" + visitor.getMismatchedLocators(),
+		assertTrue("To DOM and back should equal same Activity:\n" + mismatches, mismatches.isEmpty());
-				visitor.isEqual());
 
 		return parsedActivity;
 	}

li.strolch.persistence.postgresql/src/main/java/li/strolch/persistence/postgresql/PostgreSqlActivityDao.java

@@ -249,7 +249,7 @@ public class PostgreSqlActivityDao extends PostgresqlDao<Activity> implements Ac
 					String id = result.getString("id");
 					SQLXML sqlxml = result.getSQLXML("asxml");
 					Activity t = parseFromXml(id, queryVisitor.getType(), sqlxml);
-					list.add(query.getActivityVisitor().visit(t));
+					list.add(t.accept(query.getActivityVisitor()));
 				}
 			}
 		} catch (SQLException e) {

li.strolch.persistence.postgresql/src/main/java/li/strolch/persistence/postgresql/PostgreSqlOrderDao.java

@@ -249,7 +249,7 @@ public class PostgreSqlOrderDao extends PostgresqlDao<Order> implements OrderDao
 					String id = result.getString("id");
 					SQLXML sqlxml = result.getSQLXML("asxml");
 					Order t = parseFromXml(id, queryVisitor.getType(), sqlxml);
-					list.add(query.getOrderVisitor().visit(t));
+					list.add(t.accept(query.getOrderVisitor()));
 				}
 			}
 		} catch (SQLException e) {

li.strolch.persistence.postgresql/src/main/java/li/strolch/persistence/postgresql/PostgreSqlResourceDao.java

@@ -241,7 +241,7 @@ public class PostgreSqlResourceDao extends PostgresqlDao<Resource> implements Re
 					String id = result.getString("id");
 					SQLXML sqlxml = result.getSQLXML("asxml");
 					Resource t = parseFromXml(id, queryVisitor.getType(), sqlxml);
-					list.add(query.getResourceVisitor().visit(t));
+					list.add(t.accept(query.getResourceVisitor()));
 				}
 			}
 		} catch (SQLException e) {

li.strolch.rest/src/main/java/li/strolch/rest/endpoint/Inspector.java

@@ -53,9 +53,7 @@ import li.strolch.model.Order;
 import li.strolch.model.Resource;
 import li.strolch.model.Tags;
 import li.strolch.model.activity.Activity;
-import li.strolch.model.json.ActivityToJsonVisitor;
+import li.strolch.model.json.StrolchElementToJsonVisitor;
-import li.strolch.model.json.OrderToJsonVisitor;
-import li.strolch.model.json.ResourceToJsonVisitor;
 import li.strolch.model.query.ActivityQuery;
 import li.strolch.model.query.OrderQuery;
 import li.strolch.model.query.ResourceQuery;
@@ -391,7 +389,7 @@ public class Inspector {
 		RestfulHelper.doOrdering(queryData, resources);
 
 		// build JSON response
-		ResourceToJsonVisitor toJsonVisitor = new ResourceToJsonVisitor();
+		StrolchElementToJsonVisitor toJsonVisitor = new StrolchElementToJsonVisitor();
 		JsonObject root = RestfulHelper.toJson(queryData, dataSetSize, resources, toJsonVisitor);
 
 		// marshall result
@@ -441,7 +439,7 @@ public class Inspector {
 		RestfulHelper.doOrdering(queryData, orders);
 
 		// build JSON response
-		OrderToJsonVisitor toJsonVisitor = new OrderToJsonVisitor();
+		StrolchElementToJsonVisitor toJsonVisitor = new StrolchElementToJsonVisitor();
 		JsonObject root = RestfulHelper.toJson(queryData, dataSetSize, orders, toJsonVisitor);
 
 		// marshall result
@@ -477,7 +475,7 @@ public class Inspector {
 		RestfulHelper.doOrdering(queryData, activities);
 
 		// build JSON response
-		ActivityToJsonVisitor toJsonVisitor = new ActivityToJsonVisitor();
+		StrolchElementToJsonVisitor toJsonVisitor = new StrolchElementToJsonVisitor();
 		JsonObject root = RestfulHelper.toJson(queryData, dataSetSize, activities, toJsonVisitor);
 
 		// marshall result
@@ -502,7 +500,8 @@ public class Inspector {
 			throw new StrolchException(MessageFormat.format("No Resource exists for {0}/{1}", type, id)); //$NON-NLS-1$
 		}
 
-		return Response.ok().entity(ResourceToJsonVisitor.toJsonString(resource)).build();
+		StrolchElementToJsonVisitor visitor = new StrolchElementToJsonVisitor();
+		return Response.ok().entity(resource.accept(visitor)).build();
 	}
 
 	@GET
@@ -584,7 +583,8 @@ public class Inspector {
 			throw new StrolchException(MessageFormat.format("No Order exists for {0}/{1}", type, id)); //$NON-NLS-1$
 		}
 
-		return Response.ok().entity(OrderToJsonVisitor.toJsonString(order)).build();
+		StrolchElementToJsonVisitor visitor = new StrolchElementToJsonVisitor();
+		return Response.ok().entity(order.accept(visitor)).build();
 	}
 
 	@GET
@@ -684,7 +684,8 @@ public class Inspector {
 			throw new StrolchException(MessageFormat.format("No Activity exists for {0}/{1}", type, id)); //$NON-NLS-1$
 		}
 
-		return Response.ok().entity(ActivityToJsonVisitor.toJsonString(activity)).build();
+		StrolchElementToJsonVisitor visitor = new StrolchElementToJsonVisitor();
+		return Response.ok().entity(activity.accept(visitor)).build();
 	}
 
 	@GET

li.strolch.rest/src/main/java/li/strolch/rest/endpoint/ModelQuery.java

@@ -23,9 +23,7 @@ import li.strolch.agent.api.ResourceMap;
 import li.strolch.model.Order;
 import li.strolch.model.Resource;
 import li.strolch.model.activity.Activity;
-import li.strolch.model.json.ActivityToJsonVisitor;
+import li.strolch.model.json.StrolchElementToJsonVisitor;
-import li.strolch.model.json.OrderToJsonVisitor;
-import li.strolch.model.json.ResourceToJsonVisitor;
 import li.strolch.model.query.ActivityQuery;
 import li.strolch.model.query.OrderQuery;
 import li.strolch.model.query.ResourceQuery;
@@ -87,8 +85,8 @@ public class ModelQuery {
 		RestfulHelper.doOrdering(queryData, resources);
 
 		// build JSON response
-		ResourceToJsonVisitor toJsonVisitor = new ResourceToJsonVisitor();
+		StrolchElementToJsonVisitor visitor = new StrolchElementToJsonVisitor();
-		JsonObject root = RestfulHelper.toJson(queryData, dataSetSize, resources, toJsonVisitor);
+		JsonObject root = RestfulHelper.toJson(queryData, dataSetSize, resources, visitor);
 
 		// marshall result
 		Gson gson = new GsonBuilder().setPrettyPrinting().create();
@@ -142,8 +140,8 @@ public class ModelQuery {
 		RestfulHelper.doOrdering(queryData, orders);
 
 		// build JSON response
-		OrderToJsonVisitor toJsonVisitor = new OrderToJsonVisitor();
+		StrolchElementToJsonVisitor visitor = new StrolchElementToJsonVisitor();
-		JsonObject root = RestfulHelper.toJson(queryData, dataSetSize, orders, toJsonVisitor);
+		JsonObject root = RestfulHelper.toJson(queryData, dataSetSize, orders, visitor);
 
 		// marshall result
 		Gson gson = new GsonBuilder().setPrettyPrinting().create();
@@ -198,8 +196,8 @@ public class ModelQuery {
 		RestfulHelper.doOrdering(queryData, activities);
 
 		// build JSON response
-		ActivityToJsonVisitor toJsonVisitor = new ActivityToJsonVisitor();
+		StrolchElementToJsonVisitor visitor = new StrolchElementToJsonVisitor();
-		JsonObject root = RestfulHelper.toJson(queryData, dataSetSize, activities, toJsonVisitor);
+		JsonObject root = RestfulHelper.toJson(queryData, dataSetSize, activities, visitor);
 
 		// marshall result
 		Gson gson = new GsonBuilder().setPrettyPrinting().create();

li.strolch.rest/src/main/java/li/strolch/rest/helper/RestfulHelper.java

@@ -57,7 +57,7 @@ public class RestfulHelper {
 	}
 
 	public static <T extends StrolchRootElement> JsonObject toJson(QueryData queryData, long dataSetSize,
-			List<T> elements, StrolchElementVisitor<T, JsonObject> toJsonVisitor) {
+			List<T> elements, StrolchElementVisitor<JsonObject> toJsonVisitor) {
 
 		// paging
 		Paging<T> paging = Paging.asPage(elements, queryData.getOffset(), queryData.getLimit());
@@ -83,7 +83,7 @@ public class RestfulHelper {
 		// add items
 		JsonArray data = new JsonArray();
 		for (T t : page) {
-			JsonObject element = toJsonVisitor.visit(t);
+			JsonObject element = t.accept(toJsonVisitor);
 			data.add(element);
 		}
 		root.add("data", data);

li.strolch.service/src/main/java/li/strolch/execution/command/ExecutionCommand.java

@@ -119,13 +119,13 @@ public abstract class ExecutionCommand extends Command implements TimeOrderingVi
 	}
 
 	@Override
-	public Void visit(Activity activity) {
+	public Void visitActivity(Activity activity) {
 		activity.getTimeOrdering().accept(this, activity);
 		return null;
 	}
 
 	@Override
-	public Void visit(Action action) {
+	public Void visitAction(Action action) {
 		ExecutionPolicy executionPolicy = getExecutionPolicy(action);
 
 		if (executionPolicy.isExecutable(action)) {