diff --git a/org.coreasm.engine/pom.xml b/org.coreasm.engine/pom.xml
index 049f7cbd..00d989c2 100644
--- a/org.coreasm.engine/pom.xml
+++ b/org.coreasm.engine/pom.xml
@@ -11,6 +11,10 @@
 		<relativePath>../org.coreasm.parent</relativePath>
 	</parent>
 
+	<properties>
+		<skipTests>true</skipTests>
+	</properties>
+
 	<build>
 		<resources>
 			<resource>
@@ -60,7 +64,7 @@
 				<artifactId>maven-surefire-plugin</artifactId>
 				<version>2.16</version>
 				<configuration>
-					<skipTests>true</skipTests>
+					<skipTests>${skipTests}</skipTests>
 					<reuseForks>false</reuseForks>
 					<forkCount>0</forkCount>
 				</configuration>
@@ -103,7 +107,7 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-compiler-plugin</artifactId>
-				<version>3.6.0</version>
+				<version>3.8.0</version>
 				<configuration>
 					<source>1.7</source>
 					<target>1.7</target>
@@ -138,7 +142,7 @@
 		<dependency>
 			<groupId>junit</groupId>
 			<artifactId>junit</artifactId>
-			<version>4.8.2</version>
+			<version>4.12</version>
 		</dependency>
 		<dependency>
 			<groupId>org.coreasm</groupId>
diff --git a/org.coreasm.engine/src/org/coreasm/engine/Specification.java b/org.coreasm.engine/src/org/coreasm/engine/Specification.java
index 3666e54f..ba3f046c 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/Specification.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/Specification.java
@@ -323,11 +323,12 @@ public Set<String> getPluginNames() {
 	 * @see #loadSpec(String)
 	 */
 	public static ArrayList<SpecLine> loadSpec(Specification mainSpec, String fileName) throws IOException {
-		String specRoot = "";
-		if (mainSpec != null) 
-			specRoot = mainSpec.getFileDir() + File.separator;
-
-		return loadSpec(specRoot + fileName);
+		if (mainSpec == null) {
+			return loadSpec(new File(fileName));
+		}
+		else {
+			return loadSpec(new File(mainSpec.getFileDir(), fileName));
+		}
 	}
 
 	/**
diff --git a/org.coreasm.engine/src/org/coreasm/engine/absstorage/AbstractStorage.java b/org.coreasm.engine/src/org/coreasm/engine/absstorage/AbstractStorage.java
index 8dce06f0..db93a3a4 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/absstorage/AbstractStorage.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/absstorage/AbstractStorage.java
@@ -173,7 +173,7 @@ public interface AbstractStorage extends State {
 	 * This method should only be called when there is a state in the stack.
 	 * 
 	 * @param u the update multiset
-	 * @see #pushState()
+	 * @see #pushState(String pluginName)
 	 */
 	public void apply(Set<Update> u);
 	
diff --git a/org.coreasm.engine/src/org/coreasm/engine/absstorage/HashStorage.java b/org.coreasm.engine/src/org/coreasm/engine/absstorage/HashStorage.java
index ca1bb38b..71129f57 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/absstorage/HashStorage.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/absstorage/HashStorage.java
@@ -140,7 +140,8 @@ private Stack<String> getUpdateStackPluginNames() {
 	private boolean isStateStacked() {
 		return !getUpdateStack().isEmpty();
 	}
-	
+
+	@Override
 	public void initAbstractStorage() {
 		clearState();
 		
@@ -217,7 +218,8 @@ private void loadVocabularyExtender(VocabularyExtender ve) throws NameConflictEx
 				addRule(name, veRules.get(name));
 			}
 	}
-	
+
+	@Override
 	public synchronized void fireUpdateSet(Set<Update> updateSet) throws InvalidLocationException {
 		// Cannot fire updates while state stack is not empty.
 		// Doing this check will allow us to bypass calling setValue(...)
@@ -231,16 +233,14 @@ public synchronized void fireUpdateSet(Set<Update> updateSet) throws InvalidLoca
 		monitoredCache.clear();
 	}
 
+	@Override
 	public Element getChosenProgram(Element agent) {
-		Element p = null;
-		Element s = null;
-		
 		try {
-			p = getValue(new Location(PROGRAM_FUNCTION_NAME, ElementList.create(agent)));
+			Element p = getValue(new Location(PROGRAM_FUNCTION_NAME, ElementList.create(agent)));
 			if (p instanceof RuleElement)
 				return p;
 			else {
-				capi.error("Value of program(" + s + ") is not a Rule element.");
+				capi.error("Value of program(" + agent + ") is not a Rule element.");
 				return Element.UNDEF;
 			}
 		} catch (InvalidLocationException e) {
@@ -250,23 +250,6 @@ public Element getChosenProgram(Element agent) {
 		}
 	}
 
-//	/**
-//	 * @see org.coreasm.engine.absstorage.AbstractStorage#getState()
-//	 */
-//	public State getState() {
-//		return this;
-//	}
-//
-//	/** 
-//	 * @see org.coreasm.engine.absstorage.AbstractStorage#setState(org.coreasm.engine.absstorage.State)
-//	 */
-//	public void setState(State newState) {
-//		if (!stateStacked) 
-//			this.state = newState;
-//		else
-//			throw new EngineError("Cannot set state when the state stack is not empty.");
-//	}
-//
 	public Element getValue(Location l) throws InvalidLocationException {
 		Element e = null;
 		FunctionElement f = this.getFunction(l.name);
@@ -339,6 +322,7 @@ private Element getStackedValue(Location loc) {
 		return null;
 	}
 
+	@Override
 	public void aggregateUpdates() {
 		logger.debug("Aggregating updates.");
 		UpdateMultiset updateInsts = capi.getScheduler().getUpdateInstructions();
@@ -359,14 +343,15 @@ public void aggregateUpdates() {
 	/**
 	 * @see AbstractStorage#compose(UpdateMultiset, UpdateMultiset)
 	 */
+	@Override
 	public UpdateMultiset compose(UpdateMultiset updateSet1, UpdateMultiset updateSet2) {
 		// instantiate engine composition API, and set update multiset
 		CompositionAPIImp compAPI = new CompositionAPIImp();
 		compAPI.setUpdateInstructions(updateSet1, updateSet2);
 		
-		for (Aggregator p: aggregatorPlugins) 
+		for (Aggregator p : aggregatorPlugins)
 //			synchronized (p) {
-				((Aggregator)p).compose(compAPI);
+				p.compose(compAPI);
 //			}
 		
 //		if (compAPI.isConsistent() == false)
@@ -379,16 +364,17 @@ public UpdateMultiset compose(UpdateMultiset updateSet1, UpdateMultiset updateSe
 	/**
 	 * @see AbstractStorage#performAggregation(UpdateMultiset)
 	 */
+	@Override
 	public Set<Update> performAggregation(UpdateMultiset updateInsts) {
 		// instantiate engine aggregation API, and set update multiset
 		AggregationAPIImp aggAPI = new AggregationAPIImp();
 		aggAPI.setUpdateInstructions(updateInsts);
 		
 		// for each plugin
-		for (Aggregator p: aggregatorPlugins) 
-			((Aggregator)p).aggregateUpdates(aggAPI);
+		for (Aggregator p : aggregatorPlugins)
+			p.aggregateUpdates(aggAPI);
 		
-		if (aggAPI.isConsistent() == false) {
+		if (!aggAPI.isConsistent()) {
 			String msg = "Inconsistent aggregated results.";
 			
 			if (aggAPI.getFailedInstructions().size() > 0) {
@@ -405,7 +391,8 @@ public Set<Update> performAggregation(UpdateMultiset updateInsts) {
 		// get resultant updates from agg API
 		return aggAPI.getResultantUpdates();
 	}
-	
+
+	@Override
 	public synchronized boolean isConsistent(Collection<Update> updateSet) {
 		Collection<Update> uSet = updateSet;
 		lastInconsistentUpdates = null;
@@ -430,6 +417,7 @@ public synchronized boolean isConsistent(Collection<Update> updateSet) {
 		return true;
 	}
 
+	@Override
 	public Element getNewElement() {
 		return new Element();
 	}
@@ -481,8 +469,9 @@ public void popState(String pluginName) {
 	 * This method should only be called when there is a state in the stack.
 	 * 
 	 * @param updates the update multiset
-	 * @see #pushState()
+	 * @see #pushState(String pluginName)
 	 */
+	@Override
 	public synchronized void apply(Set<Update> updates) {
 		if (isStateStacked()) {
 			Stack<Map<Location, Element>> updateStack = getUpdateStack();
@@ -541,6 +530,7 @@ public Set<Location> getLocations() {
 	 * Return <code>true</code> if the given name is the name
 	 * of a function in the state.
 	 */
+	@Override
 	public boolean isFunctionName(String token) {
 		return getFunction(token) != null;
 	}
@@ -549,6 +539,7 @@ public boolean isFunctionName(String token) {
 	 * Return <code>true</code> if the given name is the name
 	 * of a function in the state.
 	 */
+	@Override
 	public boolean isUniverseName(String token) {
 		return getUniverse(token) != null;
 	}
@@ -557,23 +548,14 @@ public boolean isUniverseName(String token) {
 	 * Return <code>true<code> if the given name is the name
 	 * of a rule in the state.
 	 */
+	@Override
 	public boolean isRuleName(String token) {
 		return getRule(token) != null;
 	}
 
+	@Override
 	public synchronized void clearState() {
 		state = new HashState();
-		/*
-		 * The following universe and functions are moved to Kernel
-		try {
-			state.addFunction(SELF_FUNCTION_NAME, new MapFunction(Element.UNDEF));
-			state.addFunction(PROGRAM_FUNCTION_NAME, new MapFunction(Element.UNDEF));
-			state.addUniverse(AGENTS_UNIVERSE_NAME, new UniverseElement());
-		} catch (NameConflictException e) {
-			// This should not happen!
-			throw new EngineError(e);
-		}
-		/**/
 	}
 
     public String getFunctionName(FunctionElement function) {
@@ -584,6 +566,7 @@ public String toString() {
 		return state.toString();
 	}
 
+	@Override
 	public Set<Update> getLastInconsistentUpdate() {
 		return lastInconsistentUpdates;
 	}
@@ -637,9 +620,17 @@ public void setValue(List<? extends Element> args, Element value) throws Unmodif
 		public E getValue(String name) {
 			return table.get(name);
 		}
+
+		public String getKey(E value) {
+			for (Entry<String, E> f: table.entrySet()) {
+				if (f.getValue().equals(value))
+					return f.getKey();
+			}
+			return null;
+		}
 		
 		public Collection<E> values() {
-			return (Collection<E>)table.values();
+			return table.values();
 		}
 
 		public Collection<String> getNames() {
@@ -723,10 +714,17 @@ public HashState() {
 			functionElements.setValue(FUNCTION_ELEMENT_FUNCTION_NAME, functionElements);
 		}
 
+		@Override
 		public Map<String,AbstractUniverse> getUniverses() {
 			return universeElements.getTableClone();
 		}
 
+		@Override
+		public AbstractUniverse getUniverse(String name) {
+			return universeElements.getValue(name);
+		}
+
+		@Override
 		public synchronized void addUniverse(String name, AbstractUniverse universe) throws NameConflictException {
 			if (universe == null)
 				throw new NullPointerException();
@@ -735,10 +733,32 @@ public synchronized void addUniverse(String name, AbstractUniverse universe) thr
 			universeElements.setValue(name, universe);
 		}
 
+		@Override
 		public Map<String,FunctionElement> getFunctions() {
 			return functionElements.getTableClone();
 		}
 
+		@Override
+		public FunctionElement getFunction(String name) {
+			FunctionElement res = functionElements.getValue(name);
+			if (res == null)
+				res = universeElements.getValue(name);
+			return res;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.coreasm.engine.absstorage.State#getFunctionName(org.coreasm.engine.absstorage.FunctionElement)
+		 */
+		@Override
+		public String getFunctionName(FunctionElement function) {
+			String result = functionElements.getKey(function);
+			if (result == null && function instanceof AbstractUniverse) {
+				result = universeElements.getKey((AbstractUniverse)function);
+			}
+			return result;
+		}
+
+		@Override
 		public synchronized void addFunction(String name, FunctionElement function) throws NameConflictException {
 			if (function instanceof AbstractUniverse)
 				addUniverse(name, (AbstractUniverse)function);
@@ -749,10 +769,17 @@ public synchronized void addFunction(String name, FunctionElement function) thro
 			functionElements.setValue(name, function);
 		}
 
+		@Override
 		public Map<String,RuleElement> getRules() {
 			return ruleElements.getTableClone();
 		}
 
+		@Override
+		public RuleElement getRule(String name) {
+			return ruleElements.getValue(name);
+		}
+
+		@Override
 		public synchronized void addRule(String name, RuleElement rule) throws NameConflictException {
 			if (rule == null)
 				throw new NullPointerException();
@@ -761,6 +788,7 @@ public synchronized void addRule(String name, RuleElement rule) throws NameConfl
 			ruleElements.setValue(name, rule);
 		}
 
+		@Override
 		public Set<Location> getLocations() {
 			HashSet<Location> locations = new HashSet<Location>();
 			Map<String,FunctionElement> funcs = getFunctions();
@@ -770,6 +798,7 @@ public Set<Location> getLocations() {
 			return locations;
 		}
 
+		@Override
 		public Element getValue(Location loc) throws InvalidLocationException {
 			if (nameExists(loc.name)) {
 				Element id;
@@ -808,6 +837,7 @@ public Element getValue(Location loc) throws InvalidLocationException {
 		 * @throws InvalidLocationException if the location is not modifiable.
 		 * @see State#setValue(Location, Element)
 		 */
+		@Override
 		public synchronized void setValue(Location l, Element v) throws InvalidLocationException {
 			if (!nameExists(l.name)) {
 		        FunctionElement f = new MapFunction(Element.UNDEF);
@@ -836,30 +866,6 @@ public synchronized void setValue(Location l, Element v) throws InvalidLocationE
 				throw new InvalidLocationException(l + " is not a valid location.");
 		}
 
-		/*
-		public synchronized void setValue(Location l, Element v) throws InvalidLocationException {
-			if (nameExists(l.name)) {
-				Element id;
-				try {
-					id = getIdentifier(l.name);
-				} catch (IdentifierNotFoundException e) {
-					throw new InvalidLocationException(e);
-				}
-				if (id instanceof FunctionElement && ((FunctionElement)id).isModifiable())
-					try {
-						((FunctionElement) id).setValue(l.args, v);
-					} catch (UnmodifiableFunctionException e) {
-						throw new InvalidLocationException(e);
-					}
-				else
-					throw new InvalidLocationException("Not a valid location.");
-			} else {
-		        FunctionElement f = new MapFunction(Element.UNDEF);
-	            addFunction(id, f); 
-				throw new InvalidLocationException("There is no such function in the state.");
-			}
-		}
-		*/
 
 		/**
 		 * Returns the rule/function/universe in the state
@@ -870,7 +876,7 @@ public synchronized void setValue(Location l, Element v) throws InvalidLocationE
 		 * @throws IdentifierNotFoundException if there 
 		 * is no such rule/function/universe in the state
 		 */
-		public Element getIdentifier(String name)
+		private Element getIdentifier(String name)
 				throws IdentifierNotFoundException {
 			Element id = null;
 			id = (Element)universeElements.getValue(name);
@@ -901,21 +907,6 @@ private boolean nameExists(String name) {
 					|| ruleElements.containsName(name);
 		}
 
-		public FunctionElement getFunction(String name) {
-			FunctionElement res = functionElements.getValue(name);
-			if (res == null) 
-				res = universeElements.getValue(name);
-			return res;
-		}
-
-		public AbstractUniverse getUniverse(String name) {
-			return universeElements.getValue(name);
-		}
-
-		public RuleElement getRule(String name) {
-			return ruleElements.getValue(name);
-		}
-
 		public String toString() {
 			StringWriter strWriter = new StringWriter();
 			PrintWriter writer = new PrintWriter(strWriter);
@@ -977,21 +968,6 @@ public String toString() {
 			return strWriter.toString();
 		}
 
-		/* (non-Javadoc)
-         * @see org.coreasm.engine.absstorage.State#getFunctionName(org.coreasm.engine.absstorage.FunctionElement)
-         */
-        public String getFunctionName(FunctionElement function) {
-            for (Entry<String, FunctionElement> f: functionElements.table.entrySet()) {
-                if (f.getValue().equals(function))
-                	return f.getKey();
-            }
-            for (Entry<String, AbstractUniverse> u : universeElements.table.entrySet()) {
-            	if (u.getValue().equals(function))
-            		return u.getKey();
-            }
-            return null;
-        }
-
 		/*
 		 * Cut the string to a specific length
 		 */
@@ -1006,15 +982,18 @@ private String reformatFunctionValue(String value) {
 			
 			return result.toString();
 		}
-		
+
+		@Override
 		public FunctionElement getFunctionElementFunction() {
 			return functionElements;
 		}
 
+		@Override
 		public FunctionElement getRuleElementFunction() {
 			return ruleElements;
 		}
 
+		@Override
 		public FunctionElement getUniverseElementFunction() {
 			return universeElements;
 		}
diff --git a/org.coreasm.engine/src/org/coreasm/engine/absstorage/State.java b/org.coreasm.engine/src/org/coreasm/engine/absstorage/State.java
index 66919d06..f2e00e3d 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/absstorage/State.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/absstorage/State.java
@@ -52,16 +52,6 @@ public interface State {
 	public void addUniverse(String name, AbstractUniverse universe) 
 			throws NameConflictException;
 	
-//	/**
-//	 * Removes a universe from the state.
-//	 * 
-//	 * @param universe universe to be removed
-//	 * @throws IdentifierNotFoundException if no such universe
-//	 * is found in the state
-//	 */
-//	public void removeUniverse(UniverseElement universe) 
-//			throws IdentifierNotFoundException;
-	
 	/**
 	 * Set of all the functions (including universes) defined in the state.
 	 * 
@@ -95,16 +85,6 @@ public void addUniverse(String name, AbstractUniverse universe)
 	 */
 	public void addFunction(String name, FunctionElement function) 
 			throws NameConflictException;
-	
-//	/**
-//	 * Removes a function from the state.
-//	 * 
-//	 * @param function function to be removed.
-//	 * @throws IdentifierNotFoundException if there is no
-//	 * such function in the state.
-//	 */
-//	public void removeFunction(FunctionElement function) 
-//			throws IdentifierNotFoundException;
 		
 	/**
 	 * Set of all the rules defined in 
@@ -133,16 +113,6 @@ public void addFunction(String name, FunctionElement function)
 	public void addRule(String name, RuleElement rule) 
 			throws NameConflictException;
 	
-//	/**
-//	 * Removes a rule from the state.
-//	 * 
-//	 * @param rule the rule to be removed
-//	 * @throws IdentifierNotFoundException if there is no
-//	 * such rule in the state.
-//	 */
-//	public void removeRule(RuleElement rule) 
-//			throws IdentifierNotFoundException;
-	
 	/**
 	 * Set of all the defined locations in the state
 	 * that have a value other than <code>undef</code>
diff --git a/org.coreasm.engine/src/org/coreasm/engine/interpreter/InterpreterImp.java b/org.coreasm.engine/src/org/coreasm/engine/interpreter/InterpreterImp.java
index 84e36f57..ef3c1108 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/interpreter/InterpreterImp.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/interpreter/InterpreterImp.java
@@ -362,7 +362,6 @@ else if (token.equals(Kernel.KW_SELF))
 	private ASTNode interpretExpressions(ASTNode pos) throws InterpreterException {
 		final AbstractStorage storage = capi.getStorage();
 		final String gClass = pos.getGrammarClass();
-		String x = pos.getToken();
 		
 		// If the current node is a function/rule term
 		if (gClass.equals(ASTNode.FUNCTION_RULE_CLASS)) {
@@ -372,7 +371,7 @@ private ASTNode interpretExpressions(ASTNode pos) throws InterpreterException {
 				// If the current node is of the form 'x' or 'x(...)'
 				if (frNode.hasName()) {
 	
-					x = frNode.getName();
+					final String x = frNode.getName();
 					
 					// If the current node is of the form 'x' with no arguments
 					if (!frNode.hasArguments()) {
@@ -383,14 +382,14 @@ private ASTNode interpretExpressions(ASTNode pos) throws InterpreterException {
 						else {
 							// If this 'x' refers to a function in the state...
 							final FunctionElement f = storage.getFunction(x);
-//							if (storage.isFunctionName(x)) {
+
 							if (f != null) {
 								final Location l = new Location(x, ElementList.NO_ARGUMENT, f.isModifiable());
 								try {
 									pos.setNode(l, null, storage.getValue(l));
 								} catch (InvalidLocationException e) {
 									throw new EngineError("Location is invalid in 'interpretExpressions()'." + 
-											"This cannot happen!");
+											"This cannot happen!", e);
 								}
 							} else
 								// if this 'x' is not defined before...
@@ -399,11 +398,19 @@ private ASTNode interpretExpressions(ASTNode pos) throws InterpreterException {
 								}
 						}
 					} else { // if current node is 'x(...)' (with arguments)
-						
+
 						// If this 'x' refers to a function in the state...
 						FunctionElement f = storage.getFunction(x);
-						if (getEnv(x) instanceof FunctionElement)
-							f = (FunctionElement)getEnv(x);
+						String name = null;
+						if (f != null) {
+							name = x;
+						}
+
+						if (getEnv(x) instanceof FunctionElement) {
+							f = (FunctionElement) getEnv(x);
+							name = null;
+						}
+
 						if (f == null) {
 							try {
 								Element value = storage.getValue(new Location(x, ElementList.NO_ARGUMENT));
@@ -412,6 +419,7 @@ private ASTNode interpretExpressions(ASTNode pos) throws InterpreterException {
 							} catch (InvalidLocationException e) {
 							}
 						}
+
 						if (f != null) {
 							final List<ASTNode> args = frNode.getArguments();
 							// look for the parameter that needs to be evaluated
@@ -419,14 +427,13 @@ private ASTNode interpretExpressions(ASTNode pos) throws InterpreterException {
 							if (toBeEvaluated == null) {
 								// if all nodes are evaluated...
 								final ElementList vList = EngineTools.getValueList(args);
-								final String name = storage.getFunctionName(f);
 								if (name != null) {
 									final Location l = new Location(name, vList, f.isModifiable());
 									try {
 										pos.setNode(l, null, storage.getValue(l));
 									} catch (InvalidLocationException e) {
 										throw new EngineError("Location is invalid in 'interpretExpressions()'." + 
-												"This cannot happen!");
+												"This cannot happen!", e);
 									}
 								}
 								else
diff --git a/org.coreasm.engine/src/org/coreasm/engine/parser/_.java b/org.coreasm.engine/src/org/coreasm/engine/parser/_.java
deleted file mode 100644
index 398f35c0..00000000
--- a/org.coreasm.engine/src/org/coreasm/engine/parser/_.java
+++ /dev/null
@@ -1,5 +0,0 @@
-package org.coreasm.engine.parser;
-
-public class _ {
-
-}
diff --git a/org.coreasm.engine/src/org/coreasm/engine/plugin/Plugin.java b/org.coreasm.engine/src/org/coreasm/engine/plugin/Plugin.java
index 077eda44..35d99a96 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/plugin/Plugin.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/plugin/Plugin.java
@@ -51,9 +51,10 @@ public Plugin() {
 		super();
 	}
 
+	private final String pluginName = this.getClass().getSimpleName();
 	@Override
 	public final String getName() {
-		return this.getClass().getSimpleName();
+		return pluginName;
 	}
 	
 	@Override
diff --git a/org.coreasm.engine/src/org/coreasm/engine/plugins/kernelextensions/KernelExtensionsPlugin.java b/org.coreasm.engine/src/org/coreasm/engine/plugins/kernelextensions/KernelExtensionsPlugin.java
index 8a71a96d..ba03a105 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/plugins/kernelextensions/KernelExtensionsPlugin.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/plugins/kernelextensions/KernelExtensionsPlugin.java
@@ -243,10 +243,18 @@ public ASTNode interpret(Interpreter interpreter, ASTNode pos)
 					if (toBeEvaluated == null) {
 						// if all nodes are evaluated...
 						ElementList vList = EngineTools.getValueList(args);
-						
-						//look for the function in the state
-						Element value = null;
-						String fname = capi.getStorage().getFunctionName(fe);
+
+						Element value;
+						String fname;
+						if (fe.getFClass().equals(FunctionElement.FunctionClass.fcStatic)) {
+							// value can be returned directly
+							fname = null;
+						}
+						else {
+							// look for the function in the state
+							fname = capi.getStorage().getFunctionName(fe);
+						}
+
 						Location loc = null;
 						if (fname != null) {
 							try {
diff --git a/org.coreasm.engine/src/org/coreasm/engine/plugins/modularity/ModularityPlugin.java b/org.coreasm.engine/src/org/coreasm/engine/plugins/modularity/ModularityPlugin.java
index ec3b8b8d..3447233a 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/plugins/modularity/ModularityPlugin.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/plugins/modularity/ModularityPlugin.java
@@ -63,8 +63,8 @@ public class ModularityPlugin extends Plugin implements ParserPlugin,
 	
 	public static final String PLUGIN_NAME = ModularityPlugin.class.getSimpleName();
 
-	private final String[] keywords = {"CoreModule", "include"};
-	private final String[] operators = {};
+	private static final String[] keywords = {"CoreModule", "include"};
+	private static final String[] operators = {};
 	
     private Map<String, GrammarRule> parsers = null;
 
@@ -230,21 +230,18 @@ public Node map(Object[] from) {
 	private ArrayList<SpecLine> injectModules(List<SpecLine> lines, String relativePath) {
 		// CHANGE: Includes inside included specifications will be looked up relative to the including specification now
 		ArrayList<SpecLine> newSpec = new ArrayList<SpecLine>();
-		String useRegex;
-		Pattern usePattern;
-		Matcher useMatcher;
 		// compile pattern to find "include " directives using regular expression
-		useRegex = "^[\\s]*[i][n][c][l][u][d][e][\\s]+"; 
-		usePattern = Pattern.compile(useRegex);
+		String useRegex = "^[\\s]*[i][n][c][l][u][d][e][\\s]+";
+		Pattern usePattern = Pattern.compile(useRegex);
 
-		for (SpecLine line: lines) {
+		for (SpecLine line : lines) {
 			// get an "include" directive matcher object for the line
-			useMatcher = usePattern.matcher(line.text);
+			Matcher useMatcher = usePattern.matcher(line.text);
 
 			// if match found
 			if (useMatcher.find()) {
 				// are there inner include files?
-				
+
 				// get the include file name and load the file
 				String fileName = useMatcher.replaceFirst("").trim();
 				// remove potential quotation marks
@@ -252,28 +249,29 @@ private ArrayList<SpecLine> injectModules(List<SpecLine> lines, String relativeP
 					fileName = fileName.substring(1, fileName.length()-1);
 				// CHANGE: make sure that filenames have the same format to ensure that equal paths match, not only equal include statements
 				try {
-					fileName = (new File(relativePath + File.separator + fileName)).getCanonicalPath();
+					fileName = (new File(relativePath, fileName)).getCanonicalPath();
 				} catch (IOException e) {
+					logger.info("ModularityPlugin: unable to get canonical path for module '" + fileName + "'. Check " + line.fileName + ":" + line.line + ".");
 				}
+
 				if (loadedModules.contains(fileName))
-					logger.info(
-							"ModularityPlugin: Skipping module '" + fileName + "' since it's already loaded.");
-				else 
+					logger.info("ModularityPlugin: Skipping module '" + fileName + "' since it's already loaded.");
+				else
 					try {
 						loadedModules.add(fileName);
-						logger.info( 
-								"ModularityPlugin: Loading module '" + fileName + "'.");
+						logger.info("ModularityPlugin: Loading module '" + fileName + "'.");
+
 						List<SpecLine> newLines = injectModules(Specification.loadSpec(fileName), fileName.substring(0, fileName.lastIndexOf(File.separator)));
-						for (SpecLine newLine: newLines)
-							newSpec.add(newLine);
+						newSpec.addAll(newLines);
 					} catch (IOException e) {
-						capi.error("Modularity plugin cannot load module file '" 
+						capi.error("Modularity plugin cannot load module file '"
 								+ fileName + "'. The error is:" + Tools.getEOL()
 								+ e.getMessage() + Tools.getEOL()
 								+ "Check " + line.fileName + ":" + line.line + ".");
 					}
-			} else
+			} else {
 				newSpec.add(line);
+			}
 		}
 		return newSpec;
 	}
diff --git a/org.coreasm.engine/src/org/coreasm/engine/plugins/options/OptionsPlugin.java b/org.coreasm.engine/src/org/coreasm/engine/plugins/options/OptionsPlugin.java
index ff70e169..bbc282dd 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/plugins/options/OptionsPlugin.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/plugins/options/OptionsPlugin.java
@@ -252,11 +252,10 @@ public void fireOnModeTransition(EngineMode source, EngineMode target) {
 	private void loadProperties() {
 		Set<String> definedOptions = capi.getSpec().getOptions();
         ASTNode currentNode = capi.getParser().getRootNode().getFirst();
-        OptionNode optionNode = null;
         
         while (currentNode != null) {
             if (currentNode instanceof OptionNode) {
-            	optionNode = (OptionNode)currentNode;
+            	OptionNode optionNode = (OptionNode)currentNode;
             	if (definedOptions.contains(optionNode.getOptionName())) {
             		try {
             			String pluginName = optionNode.getOptionName().substring(0, optionNode.getOptionName().indexOf('.'));
diff --git a/org.coreasm.engine/src/org/coreasm/engine/plugins/set/SetPlugin.java b/org.coreasm.engine/src/org/coreasm/engine/plugins/set/SetPlugin.java
index 009a179e..df5bfc06 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/plugins/set/SetPlugin.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/plugins/set/SetPlugin.java
@@ -835,13 +835,16 @@ private Update aggregateLocationForComposition(Location l, PluginCompositionAPI
 		// value should be a set
 		if (value instanceof SetElement) {
 			Set<Element> resultSet = new HashSet<Element>(((SetElement)value).enumerate());
+			Set<Element> removeFromSet = new HashSet<Element>();
 			
 			for (Element e: resultSet) {
 				Update removeUpdate = new Update(l, e, SETREMOVE_ACTION, (Element)null, null);
 				
-				if (!uMset2.contains(removeUpdate)) 
-					resultSet.add(e);
+				if (uMset2.contains(removeUpdate))
+					removeFromSet.add(e);
 			}
+
+			resultSet.removeAll(removeFromSet);
 			
 			for (Update u: uMset2) {
 				if (u.action.equals(SETADD_ACTION)) 
diff --git a/org.coreasm.engine/src/org/coreasm/engine/plugins/signature/SignaturePlugin.java b/org.coreasm.engine/src/org/coreasm/engine/plugins/signature/SignaturePlugin.java
index 2b385c2b..6ccd4ebe 100644
--- a/org.coreasm.engine/src/org/coreasm/engine/plugins/signature/SignaturePlugin.java
+++ b/org.coreasm.engine/src/org/coreasm/engine/plugins/signature/SignaturePlugin.java
@@ -610,6 +610,7 @@ else if (typeCheckingMode == CheckMode.WARN) {
 	        						"The " + Tools.getIth(i+1) + " argument in update '" + updateToString(u) +  
 	        						"' is not a member of " + domName + " and does not match the signature of " +
 	        						"function '" + u.loc.name + ": " + func.getSignature() + "'." +
+	        						(!isUpdateSuccessful && domain instanceof UniverseElement ? " The update was not successful so it might not be added to the universe." : "") +
 	                            	getContextInfo(u);
 	                            	
 	                            	/*
@@ -652,6 +653,7 @@ else if (typeCheckingMode == CheckMode.WARN) {
 							"The value of update '" + updateToString(u) +  
 							"' is not a member of " + rangeName + " and does not match the signature of " +
 							"function '" + u.loc.name + ": " + func.getSignature() + "'." +
+							(!isUpdateSuccessful && range instanceof UniverseElement ? " The update was not successful so it might not be added to the universe." : "") +
 	                    	getContextInfo(u);
 	                    	/*
 	                    	"There is an update for function '" + u.loc.name + 
diff --git a/org.coreasm.engine/test-rsc/plugin-tests/set/Set4_compose.casm b/org.coreasm.engine/test-rsc/plugin-tests/set/Set4_compose.casm
new file mode 100644
index 00000000..23504059
--- /dev/null
+++ b/org.coreasm.engine/test-rsc/plugin-tests/set/Set4_compose.casm
@@ -0,0 +1,190 @@
+CoreASM Set4_compose
+
+use Standard
+
+init Start
+
+/*
+ * @minsteps 1
+ * @maxsteps 1
+ */
+
+function foo : -> SET
+rule Start = seqblock
+    Case1a()
+
+    Case1b()
+
+    Case2()
+
+    Case3a_add()
+
+    Case3a_remove()
+
+    Case3a_mixed()
+
+    Case3b_i()
+
+    Case3b_ii_1()
+
+    Case3b_ii_2()
+
+    Case3b_iii()
+endseqblock
+
+
+rule Case1a = {
+    seq
+        foo := {}
+    next {
+        seq
+            add 1 to foo
+        next
+            skip
+    }
+    next {
+        // @require "Case1a: {1}"
+        print "Case1a: " + foo
+    }
+}
+
+rule Case1b = {
+    seq
+        foo := {}
+    next {
+        seq
+            skip
+        next
+            add 1 to foo
+    }
+    next {
+        // @require "Case1b: {1}"
+        print "Case1b: " + foo
+    }
+}
+
+rule Case2 = {
+    seq
+        foo := {3}
+    next {
+        seq
+            skip
+        next {
+            remove 1 from foo
+            foo := {2}
+            add 2 to foo
+        }
+    }
+    next {
+        // @require "Case2: {2}"
+        print "Case2: " + foo
+    }
+}
+
+rule Case3a_add = {
+    seq
+        foo := {}
+    next {
+        seq
+            foo := {1}
+        next
+            add 2 to foo
+    }
+    next {
+        // @require "Case3a_add: {1, 2}"
+        print "Case3a_add: " + foo
+    }
+}
+
+rule Case3a_remove = {
+    seq
+        foo := {}
+    next {
+        seq
+            foo := {1, 2}
+        next
+            remove 2 from foo
+    }
+    next {
+        // @require "Case3a_remove: {1}"
+        print "Case3a_remove: " + foo
+    }
+}
+
+
+rule Case3a_mixed = {
+    seq
+        foo := {}
+    next {
+        seq
+            foo := {1, 2}
+        next {
+            remove 2 from foo
+            add 3 to foo
+        }
+    }
+    next {
+        // @require "Case3a_mixed: {1, 3}"
+        print "Case3a_mixed: " + foo
+    }
+}
+
+rule Case3b_i = {
+    seq
+        foo := {3}
+    next {
+        seq
+            add 1 to foo
+        next
+            remove 1 from foo
+    }
+    next {
+        // @require "Case3b_i: {3}"
+        print "Case3b_i: " + foo
+    }
+}
+
+rule Case3b_ii_1 = {
+    seq
+        foo := {3}
+    next {
+        seq
+            remove 3 from foo
+        next
+            add 3 to foo
+    }
+    next {
+        // @require "Case3b_ii_1: {3}"
+        print "Case3b_ii_1: " + foo
+    }
+}
+
+rule Case3b_ii_2 = {
+    seq
+        foo := {3}
+    next {
+        seq
+            remove 1 from foo
+        next
+            add 1 to foo
+    }
+    next {
+        // @require "Case3b_ii_2: {1, 3}"
+        print "Case3b_ii_2: " + foo
+    }
+}
+
+rule Case3b_iii = {
+    seq
+        foo := {3}
+    next {
+        seq
+            add 1 to foo
+        next
+            remove 2 from foo
+    }
+    next {
+        // @require "Case3b_iii: {1, 3}"
+        print "Case3b_iii: " + foo
+    }
+}
\ No newline at end of file
diff --git a/org.coreasm.engine/test/org/coreasm/engine/test/plugins/set/Set4_compose.java b/org.coreasm.engine/test/org/coreasm/engine/test/plugins/set/Set4_compose.java
new file mode 100644
index 00000000..5159f938
--- /dev/null
+++ b/org.coreasm.engine/test/org/coreasm/engine/test/plugins/set/Set4_compose.java
@@ -0,0 +1,25 @@
+package org.coreasm.engine.test.plugins.set;
+
+import org.coreasm.engine.test.TestAllCasm;
+import org.junit.BeforeClass;
+
+import java.io.File;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.util.LinkedList;
+
+public class Set4_compose extends TestAllCasm {
+
+	@BeforeClass
+	public static void onlyOnce() {
+		URL url = Set4_compose.class.getClassLoader().getResource(".");
+
+		try {
+			testFiles = new LinkedList<File>();
+			getTestFile(testFiles, new File(url.toURI()).getParentFile(), Set4_compose.class);
+		}
+		catch (URISyntaxException e) {
+			e.printStackTrace();
+		}
+	}
+}
diff --git a/org.coreasm.parent/pom.xml b/org.coreasm.parent/pom.xml
index 68a81859..f70c2c45 100644
--- a/org.coreasm.parent/pom.xml
+++ b/org.coreasm.parent/pom.xml
@@ -98,10 +98,11 @@
 		<plugin>
 			<groupId>org.apache.maven.plugins</groupId>
 			<artifactId>maven-compiler-plugin</artifactId>
-			<version>3.1</version>
+			<version>3.8.0</version>
 			<configuration>
 				<source>1.7</source>
 				<target>1.7</target>
+				<useIncrementalCompilation>false</useIncrementalCompilation>
 			</configuration>
 			</plugin>
 
diff --git a/org.coreasm.ui.carma/pom.xml b/org.coreasm.ui.carma/pom.xml
index 360c722b..cec3b479 100644
--- a/org.coreasm.ui.carma/pom.xml
+++ b/org.coreasm.ui.carma/pom.xml
@@ -60,9 +60,11 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-compiler-plugin</artifactId>
+				<version>3.8.0</version>
 				<configuration>
 					<source>1.7</source>
 					<target>1.7</target>
+					<useIncrementalCompilation>false</useIncrementalCompilation>
 				</configuration>
 			</plugin>
 
@@ -87,4 +89,4 @@
 		</dependency>
 	</dependencies>
 	<groupId>org.coreasm</groupId>
-</project>
\ No newline at end of file
+</project>