diff --git a/src/main/java/com/metaweb/gridworks/browsing/facets/TextSearchFacet.java b/src/main/java/com/metaweb/gridworks/browsing/facets/TextSearchFacet.java
index 08d7e661e..163369b3e 100644
--- a/src/main/java/com/metaweb/gridworks/browsing/facets/TextSearchFacet.java
+++ b/src/main/java/com/metaweb/gridworks/browsing/facets/TextSearchFacet.java
@@ -10,7 +10,7 @@ import com.metaweb.gridworks.browsing.FilteredRows;
 import com.metaweb.gridworks.browsing.filters.ExpressionStringComparisonRowFilter;
 import com.metaweb.gridworks.browsing.filters.RowFilter;
 import com.metaweb.gridworks.expr.Evaluable;
-import com.metaweb.gridworks.expr.VariableExpr;
+import com.metaweb.gridworks.expr.ast.VariableExpr;
 import com.metaweb.gridworks.model.Project;
 
 public class TextSearchFacet implements Facet {
diff --git a/src/main/java/com/metaweb/gridworks/commands/util/PreviewExpressionCommand.java b/src/main/java/com/metaweb/gridworks/commands/util/PreviewExpressionCommand.java
index 0a221b83f..4966b9871 100644
--- a/src/main/java/com/metaweb/gridworks/commands/util/PreviewExpressionCommand.java
+++ b/src/main/java/com/metaweb/gridworks/commands/util/PreviewExpressionCommand.java
@@ -17,7 +17,7 @@ import com.metaweb.gridworks.expr.Evaluable;
 import com.metaweb.gridworks.expr.ExpressionUtils;
 import com.metaweb.gridworks.expr.HasFields;
 import com.metaweb.gridworks.expr.Parser;
-import com.metaweb.gridworks.expr.Parser.ParserException;
+import com.metaweb.gridworks.expr.ParsingException;
 import com.metaweb.gridworks.model.Cell;
 import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.model.Row;
@@ -85,7 +85,7 @@ public class PreviewExpressionCommand extends Command {
 					}
 				}
 				writer.endArray();
-			} catch (ParserException e) {
+			} catch (ParsingException e) {
                 writer.key("code"); writer.value("error");
                 writer.key("type"); writer.value("parser");
                 writer.key("message"); writer.value(e.getMessage());
diff --git a/src/main/java/com/metaweb/gridworks/expr/Parser.java b/src/main/java/com/metaweb/gridworks/expr/Parser.java
index 6bcfab198..27711cdc2 100644
--- a/src/main/java/com/metaweb/gridworks/expr/Parser.java
+++ b/src/main/java/com/metaweb/gridworks/expr/Parser.java
@@ -6,25 +6,23 @@ import java.util.List;
 import com.metaweb.gridworks.expr.Scanner.NumberToken;
 import com.metaweb.gridworks.expr.Scanner.Token;
 import com.metaweb.gridworks.expr.Scanner.TokenType;
+import com.metaweb.gridworks.expr.ast.ControlCallExpr;
+import com.metaweb.gridworks.expr.ast.FieldAccessorExpr;
+import com.metaweb.gridworks.expr.ast.FunctionCallExpr;
+import com.metaweb.gridworks.expr.ast.LiteralExpr;
+import com.metaweb.gridworks.expr.ast.OperatorCallExpr;
+import com.metaweb.gridworks.expr.ast.VariableExpr;
 
 public class Parser {
 	protected Scanner 	_scanner;
 	protected Token 	_token;
 	protected Evaluable _root;
 	
-	static public class ParserException extends Exception {
-        private static final long serialVersionUID = 155004505172098755L;
-
-        protected ParserException(String message) {
-	        super(message);
-	    }
-	}
-	
-	public Parser(String s) throws ParserException {
+	public Parser(String s) throws ParsingException {
 		this(s, 0, s.length());
 	}
 	
-	public Parser(String s, int from, int to) throws ParserException {
+	public Parser(String s, int from, int to) throws ParsingException {
 		_scanner = new Scanner(s, from, to);
 		_token = _scanner.next();
 		
@@ -39,13 +37,13 @@ public class Parser {
 		_token = _scanner.next();
 	}
 	
-	protected ParserException makeException(String desc) {
+	protected ParsingException makeException(String desc) {
 		int index = _token != null ? _token.start : _scanner.getIndex();
 		
-		return new ParserException("Parsing error at offset " + index + ": " + desc);
+		return new ParsingException("Parsing error at offset " + index + ": " + desc);
 	}
 	
-	protected Evaluable parseExpression() throws ParserException {
+	protected Evaluable parseExpression() throws ParsingException {
 		Evaluable sub = parseSubExpression();
 		
 		while (_token != null && 
@@ -64,7 +62,7 @@ public class Parser {
 		return sub;
 	}
 	
-	protected Evaluable parseSubExpression() throws ParserException {
+	protected Evaluable parseSubExpression() throws ParsingException {
 		Evaluable sub = parseTerm();
 		
 		while (_token != null && 
@@ -83,7 +81,7 @@ public class Parser {
 		return sub;
 	}
 	
-	protected Evaluable parseTerm() throws ParserException {
+	protected Evaluable parseTerm() throws ParsingException {
 		Evaluable factor = parseFactor();
 		
 		while (_token != null && 
@@ -102,7 +100,7 @@ public class Parser {
 		return factor;
 	}
 	
-	protected Evaluable parseFactor() throws ParserException {
+	protected Evaluable parseFactor() throws ParsingException {
 		if (_token == null) {
 			throw makeException("Expression ends too early");
 		}
@@ -207,7 +205,7 @@ public class Parser {
 		return eval;
 	}
 	
-	protected List<Evaluable> parseExpressionList(String closingDelimiter) throws ParserException {
+	protected List<Evaluable> parseExpressionList(String closingDelimiter) throws ParsingException {
 		List<Evaluable> l = new LinkedList<Evaluable>();
 		
 		if (_token != null && 
diff --git a/src/main/java/com/metaweb/gridworks/expr/ParsingException.java b/src/main/java/com/metaweb/gridworks/expr/ParsingException.java
new file mode 100644
index 000000000..07fed1bca
--- /dev/null
+++ b/src/main/java/com/metaweb/gridworks/expr/ParsingException.java
@@ -0,0 +1,16 @@
+/**
+ * 
+ */
+package com.metaweb.gridworks.expr;
+
+public class ParsingException extends Exception {
+    private static final long serialVersionUID = 155004505172098755L;
+
+    public ParsingException(String message) {
+        super(message);
+    }
+    
+    public ParsingException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/metaweb/gridworks/expr/ControlCallExpr.java b/src/main/java/com/metaweb/gridworks/expr/ast/ControlCallExpr.java
similarity index 79%
rename from src/main/java/com/metaweb/gridworks/expr/ControlCallExpr.java
rename to src/main/java/com/metaweb/gridworks/expr/ast/ControlCallExpr.java
index 7364c88cf..0be9fd6c6 100644
--- a/src/main/java/com/metaweb/gridworks/expr/ControlCallExpr.java
+++ b/src/main/java/com/metaweb/gridworks/expr/ast/ControlCallExpr.java
@@ -1,7 +1,10 @@
-package com.metaweb.gridworks.expr;
+package com.metaweb.gridworks.expr.ast;
 
 import java.util.Properties;
 
+import com.metaweb.gridworks.expr.Control;
+import com.metaweb.gridworks.expr.Evaluable;
+
 public class ControlCallExpr implements Evaluable {
 	final protected Evaluable[] _args;
 	final protected Control     _control;
diff --git a/src/main/java/com/metaweb/gridworks/expr/FieldAccessorExpr.java b/src/main/java/com/metaweb/gridworks/expr/ast/FieldAccessorExpr.java
similarity index 75%
rename from src/main/java/com/metaweb/gridworks/expr/FieldAccessorExpr.java
rename to src/main/java/com/metaweb/gridworks/expr/ast/FieldAccessorExpr.java
index 389d022f5..7b77dbb31 100644
--- a/src/main/java/com/metaweb/gridworks/expr/FieldAccessorExpr.java
+++ b/src/main/java/com/metaweb/gridworks/expr/ast/FieldAccessorExpr.java
@@ -1,7 +1,12 @@
-package com.metaweb.gridworks.expr;
+package com.metaweb.gridworks.expr.ast;
 
 import java.util.Properties;
 
+import com.metaweb.gridworks.expr.EvalError;
+import com.metaweb.gridworks.expr.Evaluable;
+import com.metaweb.gridworks.expr.ExpressionUtils;
+import com.metaweb.gridworks.expr.HasFields;
+
 public class FieldAccessorExpr implements Evaluable {
 	final protected Evaluable 	_inner;
 	final protected String		_fieldName;
diff --git a/src/main/java/com/metaweb/gridworks/expr/FunctionCallExpr.java b/src/main/java/com/metaweb/gridworks/expr/ast/FunctionCallExpr.java
similarity index 79%
rename from src/main/java/com/metaweb/gridworks/expr/FunctionCallExpr.java
rename to src/main/java/com/metaweb/gridworks/expr/ast/FunctionCallExpr.java
index f68cf0043..6734d7f70 100644
--- a/src/main/java/com/metaweb/gridworks/expr/FunctionCallExpr.java
+++ b/src/main/java/com/metaweb/gridworks/expr/ast/FunctionCallExpr.java
@@ -1,7 +1,11 @@
-package com.metaweb.gridworks.expr;
+package com.metaweb.gridworks.expr.ast;
 
 import java.util.Properties;
 
+import com.metaweb.gridworks.expr.Evaluable;
+import com.metaweb.gridworks.expr.ExpressionUtils;
+import com.metaweb.gridworks.expr.Function;
+
 public class FunctionCallExpr implements Evaluable {
 	final protected Evaluable[] _args;
 	final protected Function	_function;
diff --git a/src/main/java/com/metaweb/gridworks/expr/LiteralExpr.java b/src/main/java/com/metaweb/gridworks/expr/ast/LiteralExpr.java
similarity index 79%
rename from src/main/java/com/metaweb/gridworks/expr/LiteralExpr.java
rename to src/main/java/com/metaweb/gridworks/expr/ast/LiteralExpr.java
index e560b9aba..7346b0b8b 100644
--- a/src/main/java/com/metaweb/gridworks/expr/LiteralExpr.java
+++ b/src/main/java/com/metaweb/gridworks/expr/ast/LiteralExpr.java
@@ -1,9 +1,11 @@
-package com.metaweb.gridworks.expr;
+package com.metaweb.gridworks.expr.ast;
 
 import java.util.Properties;
 
 import org.json.JSONObject;
 
+import com.metaweb.gridworks.expr.Evaluable;
+
 public class LiteralExpr implements Evaluable {
 	final protected Object _value;
 	
diff --git a/src/main/java/com/metaweb/gridworks/expr/OperatorCallExpr.java b/src/main/java/com/metaweb/gridworks/expr/ast/OperatorCallExpr.java
similarity index 92%
rename from src/main/java/com/metaweb/gridworks/expr/OperatorCallExpr.java
rename to src/main/java/com/metaweb/gridworks/expr/ast/OperatorCallExpr.java
index bebf81fdc..ab9a52030 100644
--- a/src/main/java/com/metaweb/gridworks/expr/OperatorCallExpr.java
+++ b/src/main/java/com/metaweb/gridworks/expr/ast/OperatorCallExpr.java
@@ -1,7 +1,10 @@
-package com.metaweb.gridworks.expr;
+package com.metaweb.gridworks.expr.ast;
 
 import java.util.Properties;
 
+import com.metaweb.gridworks.expr.Evaluable;
+import com.metaweb.gridworks.expr.ExpressionUtils;
+
 public class OperatorCallExpr implements Evaluable {
 	final protected Evaluable[] _args;
 	final protected String		_op;
diff --git a/src/main/java/com/metaweb/gridworks/expr/VariableExpr.java b/src/main/java/com/metaweb/gridworks/expr/ast/VariableExpr.java
similarity index 76%
rename from src/main/java/com/metaweb/gridworks/expr/VariableExpr.java
rename to src/main/java/com/metaweb/gridworks/expr/ast/VariableExpr.java
index 50e119e87..a50d4bbd2 100644
--- a/src/main/java/com/metaweb/gridworks/expr/VariableExpr.java
+++ b/src/main/java/com/metaweb/gridworks/expr/ast/VariableExpr.java
@@ -1,7 +1,9 @@
-package com.metaweb.gridworks.expr;
+package com.metaweb.gridworks.expr.ast;
 
 import java.util.Properties;
 
+import com.metaweb.gridworks.expr.Evaluable;
+
 public class VariableExpr implements Evaluable {
 	final protected String _name;
 	
diff --git a/src/main/java/com/metaweb/gridworks/expr/controls/ForEach.java b/src/main/java/com/metaweb/gridworks/expr/controls/ForEach.java
index 328343b33..e4f2a2216 100644
--- a/src/main/java/com/metaweb/gridworks/expr/controls/ForEach.java
+++ b/src/main/java/com/metaweb/gridworks/expr/controls/ForEach.java
@@ -12,7 +12,7 @@ import com.metaweb.gridworks.expr.ControlFunctionRegistry;
 import com.metaweb.gridworks.expr.EvalError;
 import com.metaweb.gridworks.expr.Evaluable;
 import com.metaweb.gridworks.expr.ExpressionUtils;
-import com.metaweb.gridworks.expr.VariableExpr;
+import com.metaweb.gridworks.expr.ast.VariableExpr;
 
 public class ForEach implements Control {
     public String checkArguments(Evaluable[] args) {
diff --git a/src/main/java/com/metaweb/gridworks/expr/controls/ForNonBlank.java b/src/main/java/com/metaweb/gridworks/expr/controls/ForNonBlank.java
index 557bea0d9..085f9b678 100644
--- a/src/main/java/com/metaweb/gridworks/expr/controls/ForNonBlank.java
+++ b/src/main/java/com/metaweb/gridworks/expr/controls/ForNonBlank.java
@@ -9,7 +9,7 @@ import com.metaweb.gridworks.expr.Control;
 import com.metaweb.gridworks.expr.ControlFunctionRegistry;
 import com.metaweb.gridworks.expr.Evaluable;
 import com.metaweb.gridworks.expr.ExpressionUtils;
-import com.metaweb.gridworks.expr.VariableExpr;
+import com.metaweb.gridworks.expr.ast.VariableExpr;
 
 public class ForNonBlank implements Control {
     public String checkArguments(Evaluable[] args) {
diff --git a/src/main/java/com/metaweb/gridworks/expr/controls/With.java b/src/main/java/com/metaweb/gridworks/expr/controls/With.java
index 10d87b204..d6680cf83 100644
--- a/src/main/java/com/metaweb/gridworks/expr/controls/With.java
+++ b/src/main/java/com/metaweb/gridworks/expr/controls/With.java
@@ -8,7 +8,7 @@ import org.json.JSONWriter;
 import com.metaweb.gridworks.expr.Control;
 import com.metaweb.gridworks.expr.ControlFunctionRegistry;
 import com.metaweb.gridworks.expr.Evaluable;
-import com.metaweb.gridworks.expr.VariableExpr;
+import com.metaweb.gridworks.expr.ast.VariableExpr;
 
 public class With implements Control {
     public String checkArguments(Evaluable[] args) {
diff --git a/src/main/java/com/metaweb/gridworks/expr/functions/ToDate.java b/src/main/java/com/metaweb/gridworks/expr/functions/ToDate.java
index 6f3e932fd..b1f9c700c 100644
--- a/src/main/java/com/metaweb/gridworks/expr/functions/ToDate.java
+++ b/src/main/java/com/metaweb/gridworks/expr/functions/ToDate.java
@@ -5,9 +5,9 @@ import java.util.Properties;
 import org.json.JSONException;
 import org.json.JSONWriter;
 
-import com.metaweb.gridworks.expr.CalendarParser;
-import com.metaweb.gridworks.expr.CalendarParserException;
 import com.metaweb.gridworks.expr.Function;
+import com.metaweb.gridworks.expr.util.CalendarParser;
+import com.metaweb.gridworks.expr.util.CalendarParserException;
 
 public class ToDate implements Function {
 
diff --git a/src/main/java/com/metaweb/gridworks/expr/functions/strings/Diff.java b/src/main/java/com/metaweb/gridworks/expr/functions/strings/Diff.java
index b073d59eb..3ed9a84c7 100644
--- a/src/main/java/com/metaweb/gridworks/expr/functions/strings/Diff.java
+++ b/src/main/java/com/metaweb/gridworks/expr/functions/strings/Diff.java
@@ -7,9 +7,9 @@ import org.apache.commons.lang.StringUtils;
 import org.json.JSONException;
 import org.json.JSONWriter;
 
-import com.metaweb.gridworks.expr.CalendarParser;
-import com.metaweb.gridworks.expr.CalendarParserException;
 import com.metaweb.gridworks.expr.Function;
+import com.metaweb.gridworks.expr.util.CalendarParser;
+import com.metaweb.gridworks.expr.util.CalendarParserException;
 
 public class Diff implements Function {
 
diff --git a/src/main/java/com/metaweb/gridworks/expr/CalendarParser.java b/src/main/java/com/metaweb/gridworks/expr/util/CalendarParser.java
similarity index 99%
rename from src/main/java/com/metaweb/gridworks/expr/CalendarParser.java
rename to src/main/java/com/metaweb/gridworks/expr/util/CalendarParser.java
index c372dcb17..1fa99f19e 100644
--- a/src/main/java/com/metaweb/gridworks/expr/CalendarParser.java
+++ b/src/main/java/com/metaweb/gridworks/expr/util/CalendarParser.java
@@ -1,4 +1,4 @@
-package com.metaweb.gridworks.expr;
+package com.metaweb.gridworks.expr.util;
 
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
diff --git a/src/main/java/com/metaweb/gridworks/expr/CalendarParserException.java b/src/main/java/com/metaweb/gridworks/expr/util/CalendarParserException.java
similarity index 93%
rename from src/main/java/com/metaweb/gridworks/expr/CalendarParserException.java
rename to src/main/java/com/metaweb/gridworks/expr/util/CalendarParserException.java
index 6f83cc596..f0f38c671 100644
--- a/src/main/java/com/metaweb/gridworks/expr/CalendarParserException.java
+++ b/src/main/java/com/metaweb/gridworks/expr/util/CalendarParserException.java
@@ -1,4 +1,4 @@
-package com.metaweb.gridworks.expr;
+package com.metaweb.gridworks.expr.util;
 
 // Taken from http://icecube.wisc.edu/~dglo/software/calparse/index.html
 // Copyright Dave Glowacki. Released under the BSD license.