diff --git a/common/framework/parsers/dbquery/condition.php b/common/framework/parsers/dbquery/condition.php
index b386fb894..cb5ecf690 100644
--- a/common/framework/parsers/dbquery/condition.php
+++ b/common/framework/parsers/dbquery/condition.php
@@ -5,12 +5,15 @@ namespace Rhymix\Framework\Parsers\DBQuery;
 /**
  * Condition class.
  */
-class Condition extends GenericVar
+class Condition extends VariableBase
 {
 	public $operation;
 	public $column;
 	public $var;
 	public $default;
 	public $not_null;
-	public $operator = 'AND';
+	public $filter;
+	public $minlength = 0;
+	public $maxlength = 0;
+	public $pipe = 'AND';
 }
diff --git a/common/framework/parsers/dbquery/conditiongroup.php b/common/framework/parsers/dbquery/conditiongroup.php
index caee07f1d..a5e67ce4d 100644
--- a/common/framework/parsers/dbquery/conditiongroup.php
+++ b/common/framework/parsers/dbquery/conditiongroup.php
@@ -8,5 +8,5 @@ namespace Rhymix\Framework\Parsers\DBQuery;
 class ConditionGroup
 {
 	public $conditions = array();
-	public $operator = 'AND';
+	public $pipe = 'AND';
 }
diff --git a/common/framework/parsers/dbquery/expression.php b/common/framework/parsers/dbquery/expression.php
new file mode 100644
index 000000000..5ad98717c
--- /dev/null
+++ b/common/framework/parsers/dbquery/expression.php
@@ -0,0 +1,49 @@
+<?php
+
+namespace Rhymix\Framework\Parsers\DBQuery;
+
+/**
+ * Expression class.
+ */
+class Expression
+{
+	/**
+	 * Instance properties.
+	 */
+	public $type;
+	public $value;
+	
+	/**
+	 * Constructor.
+	 * 
+	 * @param string $type
+	 * @param mixed $value
+	 */
+	public function __construct(string $type, $value = null)
+	{
+		$this->type = $type;
+		$this->value = $value;
+	}
+	
+	/**
+	 * Return the string representation of this expression.
+	 * 
+	 * @return string
+	 */
+	public function __toString()
+	{
+		switch ($this->type)
+		{
+			case 'var':
+				return ':' . $this->value;
+			case 'null':
+				return 'NULL';
+			case 'string':
+				return;
+			case 'int':
+				return $this->value;
+			
+			
+		}
+	}
+}
diff --git a/common/framework/parsers/dbquery/genericvar.php b/common/framework/parsers/dbquery/genericvar.php
deleted file mode 100644
index ca6064a13..000000000
--- a/common/framework/parsers/dbquery/genericvar.php
+++ /dev/null
@@ -1,12 +0,0 @@
-<?php
-
-namespace Rhymix\Framework\Parsers\DBQuery;
-
-/**
- * GenericVar class.
- */
-class GenericVar
-{
-	public $var;
-	public $default;
-}
diff --git a/common/framework/parsers/dbquery/orderby.php b/common/framework/parsers/dbquery/orderby.php
index 0831bc5e1..368cbe47d 100644
--- a/common/framework/parsers/dbquery/orderby.php
+++ b/common/framework/parsers/dbquery/orderby.php
@@ -5,7 +5,7 @@ namespace Rhymix\Framework\Parsers\DBQuery;
 /**
  * OrderBy class.
  */
-class OrderBy extends GenericVar
+class OrderBy extends VariableBase
 {
 	public $var;
 	public $default;
diff --git a/common/framework/parsers/dbquery/query.php b/common/framework/parsers/dbquery/query.php
index d8f151491..fbadb9c4f 100644
--- a/common/framework/parsers/dbquery/query.php
+++ b/common/framework/parsers/dbquery/query.php
@@ -10,6 +10,9 @@ class Query
 	public $name;
 	public $alias;
 	public $type;
+	public $operation;
+	public $column;
+	public $pipe;
 	public $tables = array();
 	public $columns = array();
 	public $conditions = array();
diff --git a/common/framework/parsers/dbquery/variablebase.php b/common/framework/parsers/dbquery/variablebase.php
new file mode 100644
index 000000000..215b2361e
--- /dev/null
+++ b/common/framework/parsers/dbquery/variablebase.php
@@ -0,0 +1,76 @@
+<?php
+
+namespace Rhymix\Framework\Parsers\DBQuery;
+
+/**
+ * VariableBase class.
+ */
+class VariableBase
+{
+	/**
+	 * Instance properties.
+	 */
+	public $var;
+	public $default;
+	
+	/**
+	 * Get the value of this variable.
+	 * 
+	 * @return Expression
+	 */
+	public function getValue(): Expression
+	{
+		if ($this->var)
+		{
+			return new Expression('var', $this->var);
+		}
+		else
+		{
+			return $this->getDefaultValue();
+		}
+	}
+	
+	/**
+	 * Get the default value of this variable.
+	 * 
+	 * @return Expression
+	 */
+	public function getDefaultValue(): Expression
+	{
+		// If the default value is not set, return null.
+		$val = $this->default;
+		if ($val === null)
+		{
+			return new Expression('null');
+		}
+		
+		// If the default value is a function shortcut, return an appropriate value.
+		switch ($val)
+		{
+			case 'ipaddress()':
+				return new Expression('string', \RX_CLIENT_IP);
+			case 'unixtime()':
+				return new Expression('string', time());
+			case 'curdate()':
+			case 'date()':
+				return new Expression('string', date('YmdHis'));
+			case 'sequence()':
+				return new Expression('int', getNextSequence());
+		}
+		
+		// If the default value is a calculation based on the current value, return a query string.
+		if (isset($this->column) && preg_match('/^(plus|minus|multiply)\(([0-9]+)\)$/', $val, $matches))
+		{
+			
+		}
+		
+		// If the default value is a column name, return the column name.20
+		if (\Rhymix\Framework\Parsers\DBQueryParser::isValidColumnName($val))
+		{
+			
+		}
+		
+		// Otherwise, return the literal value.
+		return new Expression('string', $val);
+	}
+}
diff --git a/common/framework/parsers/dbqueryparser.php b/common/framework/parsers/dbqueryparser.php
index a0fa28e08..d4cd3a28f 100644
--- a/common/framework/parsers/dbqueryparser.php
+++ b/common/framework/parsers/dbqueryparser.php
@@ -25,7 +25,6 @@ class DBQueryParser
 		// Parse the query.
 		$query_name = preg_replace('/\.xml$/', '', basename($filename));
 		$query = self::_parseQuery($xml, $query_name);
-		
 		return $query;
 	}
 	
@@ -46,15 +45,20 @@ class DBQueryParser
 		{
 			$query->name = $query->alias;
 		}
-		$query->type = trim($xml['action']);
+		$query->type = strtoupper($xml['action']) ?: null;
+		
+		// Load attributes that only apply to subqueries in the <conditions> block.
+		$query->operation = trim($xml['operation']) ?: null;
+		$query->column = trim($xml['column']) ?: null;
+		$query->pipe = strtoupper($xml['pipe']) ?: 'AND';
 		
 		// Load tables.
 		foreach ($xml->tables->table as $tag)
 		{
 			if (trim($tag['query']) === 'true')
 			{
-				$table = self::_parseQuery($tag);
-				$query->tables[$table->alias] = $table;
+				$subquery = self::_parseQuery($tag);
+				$query->tables[$subquery->alias] = $subquery;
 			}
 			else
 			{
@@ -77,18 +81,26 @@ class DBQueryParser
 		// Load columns.
 		foreach ($xml->columns->column as $tag)
 		{
-			$column = new DBQuery\Column;
-			$column->name = trim($tag['name']);
-			$column->alias = trim($tag['alias']) ?: null;
-			if ($column->name === '*' || preg_match('/\.\*$/', $column->name))
+			if ($tag->getName() === 'query')
 			{
-				$column->is_wildcard = true;
+				$subquery = self::_parseQuery($tag, trim($tag['id']));
+				$query->columns[] = $subquery;
 			}
-			if (!self::_isValidColumnName($column->name))
+			else
 			{
-				$column->is_expression = true;
+				$column = new DBQuery\Column;
+				$column->name = trim($tag['name']);
+				$column->alias = trim($tag['alias']) ?: null;
+				if ($column->name === '*' || preg_match('/\.\*$/', $column->name))
+				{
+					$column->is_wildcard = true;
+				}
+				if (!self::isValidColumnName($column->name))
+				{
+					$column->is_expression = true;
+				}
+				$query->columns[] = $column;
 			}
-			$query->columns[] = $column;
 		}
 		
 		// Load conditions.
@@ -131,13 +143,23 @@ class DBQueryParser
 			{
 				if ($tag = $xml->navigation->{$key})
 				{
-					$query->navigation->{$key} = new DBQuery\GenericVar;
+					$query->navigation->{$key} = new DBQuery\VariableBase;
 					$query->navigation->{$key}->var = trim($tag['var']) ?: null;
 					$query->navigation->{$key}->default = trim($tag['default']) ?: null;
 				}
 			}
 		}
 		
+		// If a SELECT query has no columns, use * by default.
+		if ($query->type === 'SELECT' && !count($query->columns))
+		{
+			$column = new DBQuery\Column;
+			$column->name = '*';
+			$column->is_wildcard = true;
+			$column->is_expression = true;
+			$query->columns[] = $column;
+		}
+		
 		// Return the complete query definition.
 		return $query;
 	}
@@ -159,19 +181,27 @@ class DBQueryParser
 				$cond = new DBQuery\Condition;
 				$cond->operation = trim($tag['operation']);
 				$cond->column = trim($tag['column']);
-				$cond->var = trim($tag['var']);
-				$cond->default = trim($tag['default']);
+				$cond->var = trim($tag['var']) ?: null;
+				$cond->default = trim($tag['default']) ?: null;
 				$cond->not_null = trim($tag['notnull'] ?: $tag['not-null']) !== '' ? true : false;
-				$cond->operator = strtoupper($tag['pipe']) ?: 'AND';
+				$cond->filter = trim($tag['filter']) ?: null;
+				$cond->minlength = intval(trim($tag['minlength']), 10);
+				$cond->maxlength = intval(trim($tag['maxlength']), 10);
+				$cond->pipe = strtoupper($tag['pipe']) ?: 'AND';
 				$result[] = $cond;
 			}
 			elseif ($name === 'group')
 			{
 				$group = new DBQuery\ConditionGroup;
 				$group->conditions = self::_parseConditions($tag);
-				$group->operator = strtoupper($tag['pipe']) ?: 'AND';
+				$group->pipe = strtoupper($tag['pipe']) ?: 'AND';
 				$result[] = $group;
 			}
+			elseif ($name === 'query')
+			{
+				$subquery = self::_parseQuery($tag);
+				$result[] = $subquery;
+			}
 		}
 		
 		return $result;
@@ -183,7 +213,7 @@ class DBQueryParser
 	 * @param string $column_name
 	 * @return bool
 	 */
-	protected static function _isValidColumnName(string $column_name): bool
+	public static function isValidColumnName(string $column_name): bool
 	{
 		if (preg_match('/^[a-z0-9_]+(?:\.[a-z0-9_]+)*$/', $column_name))
 		{