diff --git a/AlgebraicDataflowArchitectureModel/src/simulator/ConcreteResourcePath.java b/AlgebraicDataflowArchitectureModel/src/simulator/ConcreteResourcePath.java
new file mode 100644
index 0000000..3f07fb8
--- /dev/null
+++ b/AlgebraicDataflowArchitectureModel/src/simulator/ConcreteResourcePath.java
@@ -0,0 +1,11 @@
+package simulator;
+
+import models.dataConstraintModel.ResourcePath;
+
+public class ConcreteResourcePath extends ResourcePath {
+
+	public ConcreteResourcePath(ResourcePath another) {
+		super(another);
+	}
+
+}
diff --git a/AlgebraicDataflowArchitectureModel/src/simulator/Event.java b/AlgebraicDataflowArchitectureModel/src/simulator/Event.java
index 84fe389..b5a174b 100644
--- a/AlgebraicDataflowArchitectureModel/src/simulator/Event.java
+++ b/AlgebraicDataflowArchitectureModel/src/simulator/Event.java
@@ -1,7 +1,7 @@
 package simulator;
 
-import java.util.AbstractMap;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -18,6 +18,7 @@
 	private List<Expression> channelParameters;
 	private Set<Resource> inputResources;
 	private Set<Resource> outputResources;
+	private Set<Event> succEvents = new HashSet<>();
 	private Map<Integer, Map<ResourcePath, Integer>> channelSelectorToInputResource = new HashMap<>();
 	private Map<Integer, Map<ResourcePath, Integer>> channelSelectorToOutputResource = new HashMap<>();
 	
@@ -29,18 +30,17 @@
 		
 		// Extract channel parameters from the output resource.
 		List<Selector> channelSelectors = channel.getAllSelectors();
-		ResourcePath outputResPath = null;
+		Set<ResourcePath> outputResPathSet = null;
 		for (int i = 0; i < channelSelectors.size(); i++) {
-			Selector sel = channelSelectors.get(i);
-			if (outputResPath == null) {
-				for (ResourcePath resPath: channel.getOutputResources()) {
-					if (resPath.getPathParams().contains(sel.getExpression())) {
-						outputResPath = resPath;		// target output resource.
-						break;
-					}
-				}
+			if (outputResPathSet == null) {
+				outputResPathSet = channelSelectorToOutputResource.get(i).keySet();
+			} else {
+				outputResPathSet.retainAll(channelSelectorToOutputResource.get(i).keySet());
 			}
-			if (outputResPath != null) {
+		}
+		if (outputResPathSet.size() > 0) {
+			ResourcePath outputResPath = outputResPathSet.iterator().next();
+			for (int i = 0; i < channelSelectors.size(); i++) {
 				int paramIdx = channelSelectorToOutputResource.get(i).get(outputResPath);
 				Resource ancestor = outputResource;
 				while (ancestor != null) {
@@ -62,28 +62,29 @@
 
 		// Extract channel parameters from the input resource.
 		List<Selector> channelSelectors = channel.getAllSelectors();
-		ResourcePath inputResPath = null;
+		Set<ResourcePath> inputResPathSet = null;
 		for (int i = 0; i < channelSelectors.size(); i++) {
-			Selector sel = channelSelectors.get(i);
-			if (inputResPath == null) {
-				for (ResourcePath resPath: channel.getInputResources()) {
-					if (resPath.getPathParams().contains(sel.getExpression())) {
-						inputResPath = resPath;		// target input resource.
-						break;
-					}
-				}
+			if (inputResPathSet == null) {
+				inputResPathSet = channelSelectorToInputResource.get(i).keySet();
+			} else {
+				inputResPathSet.retainAll(channelSelectorToInputResource.get(i).keySet());
 			}
-			if (inputResPath != null) {
-				int paramIdx = channelSelectorToInputResource.get(i).get(inputResPath);
-				Resource ancestor = inputResource;
-				while (ancestor != null) {
-					if (ancestor.getResourceHierarchy().getNumParameters() > 0) {
-						paramIdx++;
-						if (paramIdx == inputResPath.getPathParams().size()) break;
+		}
+		if (inputResPathSet.size() > 0) {
+			ResourcePath inputResPath = inputResPathSet.iterator().next();
+			for (int i = 0; i < channelSelectors.size(); i++) {
+				if (inputResPath != null) {
+					int paramIdx = channelSelectorToInputResource.get(i).get(inputResPath);
+					Resource ancestor = inputResource;
+					while (ancestor != null) {
+						if (ancestor.getResourceHierarchy().getNumParameters() > 0) {
+							paramIdx++;
+							if (paramIdx == inputResPath.getPathParams().size()) break;
+						}
+						ancestor = ancestor.getParent();
 					}
-					ancestor = ancestor.getParent();
+					channelParameters.add(ancestor.getParameter());
 				}
-				channelParameters.add(ancestor.getParameter());
 			}
 		}
 	}
@@ -136,4 +137,16 @@
 	public Set<Resource> getOutputResources() {
 		return outputResources;
 	}
+	
+	public Set<Event> getSuccessors() {
+		return succEvents;
+	}
+	
+	public void addSuccessor(Event succEvt) {
+		succEvents.add(succEvt);
+	}
+	
+	public ConcreteResourcePath getConcreteResourcePath(ResourcePath resPath) {
+		return null;
+	}
 }
diff --git a/AlgebraicDataflowArchitectureModel/src/simulator/Simulator.java b/AlgebraicDataflowArchitectureModel/src/simulator/Simulator.java
index 0ad9b60..6e1f4b7 100644
--- a/AlgebraicDataflowArchitectureModel/src/simulator/Simulator.java
+++ b/AlgebraicDataflowArchitectureModel/src/simulator/Simulator.java
@@ -23,6 +23,7 @@
 		curState = new SystemState();
 		for (ResourceHierarchy res: model.getResourceHierarchies()) {
 			if (res.getParent() == null) {
+				// root resource
 				curState.addResource(new Resource(res));
 			}
 		}
@@ -33,10 +34,31 @@
 		return curState;
 	}
 	
-	public SystemState transition(Event inputEvent) {
-		SystemState nextState = new SystemState(curState);
+	public SystemState transition(final Event inputEvent) {
+		final SystemState nextState = new SystemState(curState);
 		nextState.addEvent(inputEvent);
 		
+		IResourceStateAccessor resouceStateAccessor = new IResourceStateAccessor() {
+			@Override
+			public Expression getCurrentStateAccessorFor(ChannelMember target, ChannelMember from) {
+				ConcreteResourcePath resPath = inputEvent.getConcreteResourcePath(target.getResource());
+				return curState.getResource(resPath).getState().getValue();
+			}
+
+			@Override
+			public Expression getNextStateAccessorFor(ChannelMember target, ChannelMember from) {
+				ConcreteResourcePath resPath = inputEvent.getConcreteResourcePath(target.getResource());
+				return nextState.getResource(resPath).getState().getValue();
+			}
+
+			@Override
+			public Expression getDirectStateAccessorFor(ResourcePath target, ResourcePath from) {
+				ConcreteResourcePath resPath = inputEvent.getConcreteResourcePath(target);
+				return curState.getResource(resPath).getState().getValue();
+			}
+		};
+
+		
 		curState = nextState;
 		return nextState;
 	}
diff --git a/AlgebraicDataflowArchitectureModel/src/simulator/SystemState.java b/AlgebraicDataflowArchitectureModel/src/simulator/SystemState.java
index 7461e67..62c1a30 100644
--- a/AlgebraicDataflowArchitectureModel/src/simulator/SystemState.java
+++ b/AlgebraicDataflowArchitectureModel/src/simulator/SystemState.java
@@ -5,6 +5,8 @@
 import java.util.List;
 import java.util.Set;
 
+import models.dataConstraintModel.ResourcePath;
+
 public class SystemState {
 	private Set<Resource> rootResources = new HashSet<>();
 	private List<Event> events = new ArrayList<>();
@@ -31,4 +33,8 @@
 	public void addEvent(Event event) {
 		events.add(event);
 	}
+	
+	public Resource getResource(ConcreteResourcePath concreteResourcePath) {
+		return null;
+	}
 }