15 files changed, 680 insertions, 499 deletions

diff --git a/src/core/parser/stack/DocumentHandler.cpp b/src/core/parser/stack/DocumentHandler.cpp
index bb04bd3..d44176a 100644
--- a/src/core/parser/stack/DocumentHandler.cpp
+++ b/src/core/parser/stack/DocumentHandler.cpp
@@ -25,6 +25,7 @@
 #include <core/model/Domain.hpp>
 #include <core/model/Project.hpp>
 #include <core/model/Typesystem.hpp>
+#include <core/parser/utils/TokenizedData.hpp>
 #include <core/parser/ParserScope.hpp>
 #include <core/parser/ParserContext.hpp>
 
@@ -372,8 +373,15 @@ bool DocumentChildHandler::convertData(Handle<FieldDescriptor> field,
 	return valid && scope().resolveValue(data, type, logger);
 }
 
-bool DocumentChildHandler::data(Variant &data)
+bool DocumentChildHandler::data(TokenizedData &data)
 {
+	// TODO: Handle this correctly
+	Variant text = data.text(WhitespaceMode::TRIM);
+	if (text == nullptr) {
+		// For now, except "no data" as success
+		return true;
+	}
+
 	// We're past the region in which explicit fields can be defined in the
 	// parent structure element
 	scope().setFlag(ParserFlag::POST_EXPLICIT_FIELDS, true);
@@ -393,11 +401,11 @@ bool DocumentChildHandler::data(Variant &data)
 	// If it is a primitive field directly, try to parse the content.
 	if (field->isPrimitive()) {
 		// Add it as primitive content.
-		if (!convertData(field, data, logger())) {
+		if (!convertData(field, text, logger())) {
 			return false;
 		}
 
-		parent->createChildDocumentPrimitive(data, fieldIdx);
+		parent->createChildDocumentPrimitive(text, fieldIdx);
 		return true;
 	}
 
@@ -411,7 +419,7 @@ bool DocumentChildHandler::data(Variant &data)
 	for (auto primitiveField : defaultFields) {
 		// Then try to parse the content using the type specification.
 		forks.emplace_back(logger().fork());
-		if (!convertData(primitiveField, data, forks.back())) {
+		if (!convertData(primitiveField, text, forks.back())) {
 			continue;
 		}
 
@@ -424,7 +432,7 @@ bool DocumentChildHandler::data(Variant &data)
 		createPath(fieldIdx, path, parent);
 
 		// Then create the primitive element
-		parent->createChildDocumentPrimitive(data);
+		parent->createChildDocumentPrimitive(text);
 		return true;
 	}
 
@@ -434,10 +442,10 @@ bool DocumentChildHandler::data(Variant &data)
 	if (defaultFields.empty()) {
 		logger().error("Got data, but structure \"" + name() +
 		                   "\" does not have any primitive field",
-		               data);
+		               text);
 	} else {
 		logger().error("Could not read data with any of the possible fields:",
-		               data);
+		               text);
 		size_t f = 0;
 		for (auto field : defaultFields) {
 			logger().note(std::string("Field ") +
@@ -471,4 +479,4 @@ namespace RttiTypes {
 const Rtti DocumentField = RttiBuilder<ousia::parser_stack::DocumentField>(
                                "DocumentField").parent(&Node);
 }
-}
\ No newline at end of file
+}
diff --git a/src/core/parser/stack/DocumentHandler.hpp b/src/core/parser/stack/DocumentHandler.hpp
index 862081c..dda7d8b 100644
--- a/src/core/parser/stack/DocumentHandler.hpp
+++ b/src/core/parser/stack/DocumentHandler.hpp
@@ -167,7 +167,7 @@ public:
 
 	bool start(Variant::mapType &args) override;
 	void end() override;
-	bool data(Variant &data) override;
+	bool data(TokenizedData &data) override;
 
 	bool fieldStart(bool &isDefault, size_t fieldIdx) override;
 
@@ -213,4 +213,4 @@ extern const Rtti DocumentField;
 }
 }
 
-#endif /* _OUSIA_PARSER_STACK_DOCUMENT_HANDLER_HPP_ */
\ No newline at end of file
+#endif /* _OUSIA_PARSER_STACK_DOCUMENT_HANDLER_HPP_ */
diff --git a/src/core/parser/stack/Handler.cpp b/src/core/parser/stack/Handler.cpp
index bf5d4ea..3d413e8 100644
--- a/src/core/parser/stack/Handler.cpp
+++ b/src/core/parser/stack/Handler.cpp
@@ -18,6 +18,7 @@
 
 #include <core/common/Exceptions.hpp>
 #include <core/common/Logger.hpp>
+#include <core/parser/utils/TokenizedData.hpp>
 #include <core/parser/ParserContext.hpp>
 
 #include "Callbacks.hpp"
@@ -130,7 +131,7 @@ bool EmptyHandler::annotationEnd(const Variant &className,
 	return true;
 }
 
-bool EmptyHandler::data(Variant &data)
+bool EmptyHandler::data(TokenizedData &data)
 {
 	// Support any data
 	return true;
@@ -184,10 +185,13 @@ bool StaticHandler::annotationEnd(const Variant &className,
 	return false;
 }
 
-bool StaticHandler::data(Variant &data)
+bool StaticHandler::data(TokenizedData &data)
 {
-	logger().error("Did not expect any data here", data);
-	return false;
+	if (data.text(WhitespaceMode::TRIM) != nullptr) {
+		logger().error("Did not expect any data here", data);
+		return false;
+	}
+	return true;
 }
 
 /* Class StaticFieldHandler */
@@ -227,12 +231,19 @@ void StaticFieldHandler::end()
 	}
 }
 
-bool StaticFieldHandler::data(Variant &data)
+bool StaticFieldHandler::data(TokenizedData &data)
 {
+	Variant text = data.text(WhitespaceMode::TRIM);
+	if (text == nullptr) {
+		// Providing no data here is ok as long as the "doHandle" callback
+		// function has already been called
+		return handled;
+	}
+
 	// Call the doHandle function if this has not been done before
 	if (!handled) {
 		handled = true;
-		doHandle(data, args);
+		doHandle(text, args);
 		return true;
 	}
 
@@ -240,7 +251,7 @@ bool StaticFieldHandler::data(Variant &data)
 	logger().error(
 	    std::string("Found data, but the corresponding argument \"") + argName +
 	        std::string("\" was already specified"),
-	    data);
+	    text);
 
 	// Print the location at which the attribute was originally specified
 	auto it = args.find(argName);
diff --git a/src/core/parser/stack/Handler.hpp b/src/core/parser/stack/Handler.hpp
index 7cda7a4..929466d 100644
--- a/src/core/parser/stack/Handler.hpp
+++ b/src/core/parser/stack/Handler.hpp
@@ -31,6 +31,7 @@ namespace ousia {
 class ParserScope;
 class ParserContext;
 class Logger;
+class TokenizedData;
 
 namespace parser_stack {
 
@@ -158,40 +159,63 @@ protected:
 	 */
 	const std::string &name() const;
 
-public:
-	/**
-	 * Virtual destructor.
-	 */
-	virtual ~Handler();
-
 	/**
 	 * Calls the corresponding function in the Callbacks instance. Sets the
 	 * whitespace mode that specifies how string data should be processed. The
 	 * calls to this function are placed on a stack by the underlying Stack
-	 * class.
+	 * class. This function should be called from the "fieldStart" callback and
+	 * the "start" callback. If no whitespace mode is pushed in the "start"
+	 * method the whitespace mode "TRIM" is implicitly assumed.
 	 *
 	 * @param whitespaceMode specifies one of the three WhitespaceMode constants
 	 * PRESERVE, TRIM or COLLAPSE.
 	 */
-	void setWhitespaceMode(WhitespaceMode whitespaceMode);
+	void pushWhitespaceMode(WhitespaceMode whitespaceMode);
 
 	/**
-	 * Calls the corresponding function in the Callbacks instance.
-	 * Registers the given token as token that should be reported to the handler
-	 * using the "token" function.
-	 *
-	 * @param token is the token string that should be reported.
+	 * Pops a previously pushed whitespace mode. Calls to this function should
+	 * occur in the "end" callback and the "fieldEnd" callback. This function
+	 * can only undo pushs that were performed by the pushWhitespaceMode()
+	 * method of the same handler.
 	 */
-	void registerToken(const std::string &token);
+	void popWhitespaceMode();
 
 	/**
-	 * Calls the corresponding function in the Callbacks instance.
-	 * Unregisters the given token, it will no longer be reported to the handler
-	 * using the "token" function.
+	 * Calls the corresponding function in the Callbacks instance. Sets the
+	 * whitespace mode that specifies how string data should be processed. The
+	 * calls to this function are placed on a stack by the underlying Stack
+	 * class. This function should be called from the "fieldStart" callback and
+	 * the "start" callback. If no whitespace mode is pushed in the "start"
+	 * method the whitespace mode "TRIM" is implicitly assumed.
 	 *
-	 * @param token is the token string that should be unregistered.
+	 * @param tokens is a list of tokens that should be reported to this handler
+	 * instance via the "token" method.
 	 */
-	void unregisterToken(const std::string &token);
+	void pushTokens(const std::vector<std::string> &tokens);
+
+	/**
+	 * Pops a previously pushed whitespace mode. Calls to this function should
+	 * occur in the "end" callback and the "fieldEnd" callback. This function
+	 * can only undo pushs that were performed by the pushWhitespaceMode()
+	 * method of the same handler.
+	 */
+	void popWhitespaceMode();
+
+
+	/**
+	 * Calls the corresponding function in the Callbacks instance. This method
+	 * registers the given tokens as tokens that are generally available, tokens
+	 * must be explicitly enabled using the "pushTokens" and "popTokens" method.
+	 * Tokens that have not been registered are not guaranteed to be reported,
+	 * even though they are 
+	 */
+	void registerTokens(const std::vector<std::string> &tokens);
+
+public:
+	/**
+	 * Virtual destructor.
+	 */
+	virtual ~Handler();
 
 	/**
 	 * Returns the command name for which the handler was created.
@@ -299,11 +323,11 @@ public:
 	 * Handler instance. Should return true if the data could be handled, false
 	 * otherwise.
 	 *
-	 * @param data is a string variant containing the character data and its
-	 * location.
+	 * @param data is an instance of TokenizedData containing the segmented
+	 * character data and its location.
 	 * @return true if the data could be handled, false otherwise.
 	 */
-	virtual bool data(Variant &data) = 0;
+	virtual bool data(TokenizedData &data) = 0;
 };
 
 /**
@@ -333,7 +357,7 @@ public:
 	                     Variant::mapType &args) override;
 	bool annotationEnd(const Variant &className,
 	                   const Variant &elementName) override;
-	bool data(Variant &data) override;
+	bool data(TokenizedData &data) override;
 
 	/**
 	 * Creates an instance of the EmptyHandler class.
@@ -359,7 +383,7 @@ public:
 	                     Variant::mapType &args) override;
 	bool annotationEnd(const Variant &className,
 	                   const Variant &elementName) override;
-	bool data(Variant &data) override;
+	bool data(TokenizedData &data) override;
 };
 
 /**
@@ -412,7 +436,7 @@ protected:
 public:
 	bool start(Variant::mapType &args) override;
 	void end() override;
-	bool data(Variant &data) override;
+	bool data(TokenizedData &data) override;
 };
 }
 }
diff --git a/src/core/parser/stack/Stack.cpp b/src/core/parser/stack/Stack.cpp
index 5b67248..309c9a0 100644
--- a/src/core/parser/stack/Stack.cpp
+++ b/src/core/parser/stack/Stack.cpp
@@ -19,6 +19,7 @@
 #include <core/common/Logger.hpp>
 #include <core/common/Utils.hpp>
 #include <core/common/Exceptions.hpp>
+#include <core/parser/utils/TokenizedData.hpp>
 #include <core/parser/ParserScope.hpp>
 #include <core/parser/ParserContext.hpp>
 
@@ -413,16 +414,24 @@ void Stack::command(const Variant &name, const Variant::mapType &args)
 	}
 }
 
-void Stack::data(const Variant &data)
+void Stack::data(TokenizedData data)
 {
-	// End handlers that already had a default field and are currently not
-	// active.
-	endOverdueHandlers();
+	// TODO: Rewrite this function for token handling
+	// TODO: This loop needs to be refactored out
+	while (!data.atEnd()) {
+		// End handlers that already had a default field and are currently not
+		// active.
+		endOverdueHandlers();
 
-	while (true) {
-		// Check whether there is any command the data can be sent to
+		const bool hasNonWhitespaceText = data.hasNonWhitespaceText();
+
+		// Check whether there is any command the data can be sent to -- if not,
+		// make sure the data actually is data
 		if (stack.empty()) {
-			throw LoggableException("No command here to receive data.", data);
+			if (hasNonWhitespaceText) {
+				throw LoggableException("No command here to receive data.", data);
+			}
+			return;
 		}
 
 		// Fetch the current command handler information
@@ -440,7 +449,10 @@ void Stack::data(const Variant &data)
 			// If the "hadDefaultField" flag is set, we already issued an error
 			// message
 			if (!info.hadDefaultField) {
-				logger().error("Did not expect any data here", data);
+				if (hasNonWhitespaceText) {
+					logger().error("Did not expect any data here", data);
+				}
+				return;
 			}
 		}
 
@@ -454,8 +466,16 @@ void Stack::data(const Variant &data)
 			// Pass the data to the current Handler instance
 			bool valid = false;
 			try {
-				Variant dataCopy = data;
-				valid = info.handler->data(dataCopy);
+				// Create a fork of the TokenizedData and let the handler work
+				// on it
+				TokenizedData dataFork = data;
+				valid = info.handler->data(dataFork);
+
+				// If the data was validly handled by the handler, commit the
+				// change
+				if (valid) {
+					data = dataFork;
+				}
 			}
 			catch (LoggableException ex) {
 				loggerFork.log(ex);
@@ -482,6 +502,19 @@ void Stack::data(const Variant &data)
 	}
 }
 
+void Stack::data(const Variant &stringData)
+{
+	// Fetch the SourceLocation of the given stringData variant
+	SourceLocation loc = stringData.getLocation();
+
+	// Create a TokenizedData instance and feed the given string data into it
+	TokenizedData tokenizedData(loc.getSourceId());
+	tokenizedData.append(stringData.asString(), loc.getStart());
+
+	// Call the actual "data" method
+	data(tokenizedData);
+}
+
 void Stack::fieldStart(bool isDefault)
 {
 	// Make sure the current handler stack is not empty
@@ -584,4 +617,4 @@ void Stack::token(Variant token)
 	// TODO
 }
 }
-}
\ No newline at end of file
+}
diff --git a/src/core/parser/stack/Stack.hpp b/src/core/parser/stack/Stack.hpp
index b67ce82..cd29b28 100644
--- a/src/core/parser/stack/Stack.hpp
+++ b/src/core/parser/stack/Stack.hpp
@@ -44,6 +44,7 @@ namespace ousia {
 // Forward declarations
 class ParserContext;
 class Logger;
+class TokenizedData;
 
 namespace parser_stack {
 
@@ -292,13 +293,24 @@ public:
 	void command(const Variant &name, const Variant::mapType &args);
 
 	/**
-	 * Function that shuold be called whenever character data is found in the
+	 * Function that should be called whenever character data is found in the
 	 * input stream. May only be called if the currently is a command on the
 	 * stack.
 	 *
-	 * @param data is a string variant containing the data that has been found.
+	 * @param data is a TokenizedData instance containing the pre-segmented data
+	 * that should be read.
+	 */
+	void data(TokenizedData data);
+
+	/**
+	 * Function that shuold be called whenever character data is found in the
+	 * input stream. The given string variant is converted into a TokenizedData
+	 * instance internally.
+	 *
+	 * @param stringData is a string variant containing the data that has been
+	 * found.
 	 */
-	void data(const Variant &data);
+	void data(const Variant &stringData);
 
 	/**
 	 * Function that should be called whenever a new field starts. Fields of the
diff --git a/src/core/parser/utils/SourceOffsetVector.hpp b/src/core/parser/utils/SourceOffsetVector.hpp
index d15055a..aaebe7d 100644
--- a/src/core/parser/utils/SourceOffsetVector.hpp
+++ b/src/core/parser/utils/SourceOffsetVector.hpp
@@ -127,7 +127,7 @@ public:
 	 * read.
 	 * @return a pair containing start and end source offset.
 	 */
-	std::pair<SourceOffset, SourceOffset> loadOffset(size_t idx)
+	std::pair<SourceOffset, SourceOffset> loadOffset(size_t idx) const
 	{
 		// Special treatment for the last character
 		const size_t count = lens.size();
@@ -157,7 +157,31 @@ public:
 	/**
 	 * Returns the number of characters for which offsets are stored.
 	 */
-	size_t size() { return lens.size(); }
+	size_t size() const { return lens.size(); }
+
+	/**
+	 * Trims the length of the TokenizedData instance to the given length.
+	 * Removes all token matches that lie within the trimmed region.
+	 *
+	 * @param length is the number of characters to which the TokenizedData
+	 * instance should be trimmed.
+	 */
+	void trim(size_t length) {
+		if (length < size()) {
+			lens.resize(length);
+			offsets.resize((length >> LOG2_OFFSET_INTERVAL) + 1);
+		}
+	}
+
+	/**
+	 * Resets the SourceOffsetVector to the state it had when it was
+	 * constructed.
+	 */
+	void clear() {
+		lens.clear();
+		offsets.clear();
+		lastEnd = 0;
+	}
 };
 }
 
diff --git a/src/core/parser/utils/Token.cpp b/src/core/parser/utils/Token.cpp
deleted file mode 100644
index 8bcdbb5..0000000
--- a/src/core/parser/utils/Token.cpp
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
-    Ousía
-    Copyright (C) 2014  Benjamin Paaßen, Andreas Stöckel
-
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
-*/
-
-#include "Token.hpp"
-
-namespace ousia {
-// Stub to make sure Tokens.hpp is valid
-}
-
diff --git a/src/core/parser/utils/Token.hpp b/src/core/parser/utils/Token.hpp
deleted file mode 100644
index f907450..0000000
--- a/src/core/parser/utils/Token.hpp
+++ /dev/null
@@ -1,142 +0,0 @@
-/*
-    Ousía
-    Copyright (C) 2014  Benjamin Paaßen, Andreas Stöckel
-
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
-*/
-
-/**
- * @file Token.hpp
- *
- * Definition of the TokenId id and constants for some special tokens.
- *
- * @author Andreas Stöckel (astoecke@techfak.uni-bielefeld.de)
- */
-
-#ifndef _OUSIA_TOKEN_HPP_
-#define _OUSIA_TOKEN_HPP_
-
-#include <cstdint>
-#include <limits>
-#include <string>
-
-#include <core/common/Location.hpp>
-
-namespace ousia {
-
-/**
- * The TokenId is used to give each token id a unique id.
- */
-using TokenId = uint32_t;
-
-/**
- * Type used for storing token lengths.
- */
-using TokenLength = uint16_t;
-
-/**
- * Namespace containing constants for TokenId instances with special meaning.
- */
-namespace Tokens {
-/**
- * Token which is not a token.
- */
-constexpr TokenId Empty = std::numeric_limits<TokenId>::max();
-
-/**
- * Token which represents data (represented as TokenizedData).
- */
-constexpr TokenId Data = std::numeric_limits<TokenId>::max() - 1;
-
-/**
- * Token which represents a newline token.
- */
-constexpr TokenId Newline = std::numeric_limits<TokenId>::max() - 2;
-
-/**
- * Token which represents a paragraph token -- issued if two consecutive
- * newlines occur with optionally any amout of whitespace between them.
- */
-constexpr TokenId Paragraph = std::numeric_limits<TokenId>::max() - 3;
-
-/**
- * Token which represents an indentation token -- issued if the indentation of
- * this line is larget than the indentation of the previous line.
- */
-constexpr TokenId Indentation = std::numeric_limits<TokenId>::max() - 4;
-
-/**
- * Maximum token id to be used. Tokens allocated for users should not surpass
- * this value.
- */
-constexpr TokenId MaxTokenId = std::numeric_limits<TokenId>::max() - 255;
-}
-
-/**
- * The Token structure describes a token discovered by the Tokenizer or read
- * from the TokenizedData struct.
- */
-struct Token {
-	/**
-	 * Id of the id of this token.
-	 */
-	TokenId id;
-
-	/**
-	 * String that was matched.
-	 */
-	std::string content;
-
-	/**
-	 * Location from which the string was extracted.
-	 */
-	SourceLocation location;
-
-	/**
-	 * Default constructor.
-	 */
-	Token() : id(Tokens::Empty) {}
-
-	/**
-	 * Constructor of the Token struct.
-	 *
-	 * @param id represents the token id.
-	 * @param content is the string content that has been extracted.
-	 * @param location is the location of the extracted string content in the
-	 * source file.
-	 */
-	Token(TokenId id, const std::string &content, SourceLocation location)
-	    : id(id), content(content), location(location)
-	{
-	}
-
-	/**
-	 * Constructor of the Token struct, only initializes the token id
-	 *
-	 * @param id is the id corresponding to the id of the token.
-	 */
-	Token(TokenId id) : id(id) {}
-
-	/**
-	 * The getLocation function allows the tokens to be directly passed as
-	 * parameter to Logger or LoggableException instances.
-	 *
-	 * @return a reference at the location field
-	 */
-	const SourceLocation &getLocation() const { return location; }
-};
-}
-
-#endif /* _OUSIA_TOKENS_HPP_ */
-
diff --git a/src/core/parser/utils/TokenTrie.cpp b/src/core/parser/utils/TokenTrie.cpp
index 80cc945..a45d3ff 100644
--- a/src/core/parser/utils/TokenTrie.cpp
+++ b/src/core/parser/utils/TokenTrie.cpp
@@ -22,12 +22,12 @@ namespace ousia {
 
 /* Class DynamicTokenTree::Node */
 
-TokenTrie::Node::Node() : type(Tokens::Empty) {}
+TokenTrie::Node::Node() : id(Tokens::Empty) {}
 
 /* Class DynamicTokenTree */
 
 bool TokenTrie::registerToken(const std::string &token,
-                              TokenId type) noexcept
+                              TokenId id) noexcept
 {
 	// Abort if the token is empty -- this would taint the root node
 	if (token.empty()) {
@@ -48,12 +48,12 @@ bool TokenTrie::registerToken(const std::string &token,
 	}
 
 	// If the resulting node already has a type set, we're screwed.
-	if (node->type != Tokens::Empty) {
+	if (node->id != Tokens::Empty) {
 		return false;
 	}
 
 	// Otherwise just set the type to the given type.
-	node->type = type;
+	node->id = id;
 	return true;
 }
 
@@ -78,7 +78,7 @@ bool TokenTrie::unregisterToken(const std::string &token) noexcept
 
 		// Reset the subtree handler if this node has another type
 		node = it->second.get();
-		if ((node->type != Tokens::Empty || node->children.size() > 1) &&
+		if ((node->id != Tokens::Empty || node->children.size() > 1) &&
 		    (i + 1 != token.size())) {
 			subtreeRoot = node;
 			subtreeKey = token[i + 1];
@@ -86,14 +86,14 @@ bool TokenTrie::unregisterToken(const std::string &token) noexcept
 	}
 
 	// If the node type is already Tokens::Empty, we cannot do anything here
-	if (node->type == Tokens::Empty) {
+	if (node->id == Tokens::Empty) {
 		return false;
 	}
 
 	// If the target node has children, we cannot delete the subtree. Set the
 	// type to Tokens::Empty instead
 	if (!node->children.empty()) {
-		node->type = Tokens::Empty;
+		node->id = Tokens::Empty;
 		return true;
 	}
 
@@ -113,7 +113,7 @@ TokenId TokenTrie::hasToken(const std::string &token) const noexcept
 		}
 		node = it->second.get();
 	}
-	return node->type;
+	return node->id;
 }
 }
 
diff --git a/src/core/parser/utils/TokenTrie.hpp b/src/core/parser/utils/TokenTrie.hpp
index b2d1539..c470acc 100644
--- a/src/core/parser/utils/TokenTrie.hpp
+++ b/src/core/parser/utils/TokenTrie.hpp
@@ -33,7 +33,7 @@
 #include <limits>
 #include <unordered_map>
 
-#include "Token.hpp"
+#include <core/common/Token.hpp>
 
 namespace ousia {
 
@@ -75,10 +75,9 @@ public:
 		ChildMap children;
 
 		/**
-		 * Reference at the corresponding token descriptor. Set to nullptr if
-		 * no token is attached to this node.
+		 * Id of the token represented by this node.
 		 */
-		TokenId type;
+		TokenId id;
 
 		/**
 		 * Default constructor, initializes the descriptor with nullptr.
@@ -99,10 +98,10 @@ public:
 	 *
 	 * @param token is the character sequence that should be registered as
 	 * token.
-	 * @param type is the descriptor that should be set for this token.
+	 * @param id is the descriptor that should be set for this token.
 	 * @return true if the operation is successful, false otherwise.
 	 */
-	bool registerToken(const std::string &token, TokenId type) noexcept;
+	bool registerToken(const std::string &token, TokenId id) noexcept;
 
 	/**
 	 * Unregisters the token from the token tree. Returns true if the token was
diff --git a/src/core/parser/utils/TokenizedData.cpp b/src/core/parser/utils/TokenizedData.cpp
index fc7bfaf..0ec56af 100644
--- a/src/core/parser/utils/TokenizedData.cpp
+++ b/src/core/parser/utils/TokenizedData.cpp
@@ -110,19 +110,19 @@ private:
 	std::vector<char> buf;
 
 	/**
-	 * Vector containing all token marks.
+	 * Vector storing all the character offsets efficiently.
 	 */
-	std::vector<TokenMark> marks;
+	SourceOffsetVector offsets;
 
 	/**
-	 * Vector storing all the character offsets efficiently.
+	 * Vector containing all token marks.
 	 */
-	SourceOffsetVector offsets;
+	mutable std::vector<TokenMark> marks;
 
 	/**
 	 * Flag indicating whether the internal "marks" vector is sorted.
 	 */
-	bool sorted;
+	mutable bool sorted;
 
 public:
 	/**
@@ -150,9 +150,12 @@ public:
 		// Extend the text regions, interpolate the source position (this may
 		// yield incorrect results)
 		const size_t size = buf.size();
-		for (SourceOffset offs = offsStart; offs < offsStart + data.size();
-		     offs++) {
-			offsets.storeOffset(offs, offs + 1);
+		for (size_t i = 0; i < data.size(); i++) {
+			if (offsStart != InvalidSourceOffset) {
+				offsets.storeOffset(offsStart + i, offsStart + i + 1);
+			} else {
+				offsets.storeOffset(InvalidSourceOffset, InvalidSourceOffset);
+			}
 		}
 
 		return size;
@@ -213,7 +216,7 @@ public:
 	 * available.
 	 */
 	bool next(Token &token, WhitespaceMode mode,
-	          const std::unordered_set<TokenId> &tokens, size_t &cursor)
+	          const std::unordered_set<TokenId> &tokens, size_t &cursor) const
 	{
 		// Sort the "marks" vector if it has not been sorted yet.
 		if (!sorted) {
@@ -222,10 +225,11 @@ public:
 		}
 
 		// Fetch the next larger TokenMark instance, make sure the token is in
-		// the "enabled" list
+		// the "enabled" list and within the buffer range
 		auto it =
 		    std::lower_bound(marks.begin(), marks.end(), TokenMark(cursor));
-		while (it != marks.end() && tokens.count(it->id) == 0) {
+		while (it != marks.end() && (tokens.count(it->id) == 0 ||
+		                             it->bufStart + it->len > buf.size())) {
 			it++;
 		}
 
@@ -304,11 +308,58 @@ public:
 	}
 
 	/**
+	 * Resets the TokenizedDataImpl instance to the state it had when it was
+	 * constructred.
+	 */
+	void clear()
+	{
+		buf.clear();
+		marks.clear();
+		offsets.clear();
+		sorted = true;
+	}
+
+	/**
+	 * Trims the length of the TokenizedDataImpl instance to the given length.
+	 *
+	 * @param length is the number of characters to which the TokenizedData
+	 * instance should be trimmed.
+	 */
+	void trim(size_t length)
+	{
+		if (length < size()) {
+			buf.resize(length);
+			offsets.trim(length);
+		}
+	}
+
+	/**
 	 * Returns the current size of the internal buffer.
 	 *
 	 * @return the size of the internal character buffer.
 	 */
-	size_t getSize() { return buf.size(); }
+	size_t size() const { return buf.size(); }
+
+	/**
+	 * Returns true if no data is in the data buffer.
+	 *
+	 * @return true if the "buf" instance has no data.
+	 */
+	bool empty() const { return buf.empty(); }
+
+	/**
+	 * Returns the current location of all data in the buffer.
+	 *
+	 * @return the location of the entire data represented by this instance.
+	 */
+	SourceLocation getLocation() const
+	{
+		if (empty()) {
+			return SourceLocation{sourceId};
+		}
+		return SourceLocation{sourceId, offsets.loadOffset(0).first,
+		                      offsets.loadOffset(size()).second};
+	}
 };
 
 /* Class TokenizedData */
@@ -335,7 +386,7 @@ size_t TokenizedData::append(char c, SourceOffset offsStart,
 
 void TokenizedData::mark(TokenId id, TokenLength len)
 {
-	impl->mark(id, impl->getSize() - len, len);
+	impl->mark(id, impl->size() - len, len);
 }
 
 void TokenizedData::mark(TokenId id, size_t bufStart, TokenLength len)
@@ -343,23 +394,67 @@ void TokenizedData::mark(TokenId id, size_t bufStart, TokenLength len)
 	impl->mark(id, bufStart, len);
 }
 
-bool TokenizedData::next(Token &token, WhitespaceMode mode)
+void TokenizedData::clear()
 {
-	return impl->next(token, mode, tokens, cursor);
+	impl->clear();
+	tokens.clear();
+	cursor = 0;
 }
 
-bool TokenizedData::text(Token &token, WhitespaceMode mode)
+void TokenizedData::trim(size_t length) { impl->trim(length); }
+
+size_t TokenizedData::size() const { return impl->size(); }
+
+bool TokenizedData::empty() const { return impl->empty(); }
+
+SourceLocation TokenizedData::getLocation() const
+{
+	return impl->getLocation();
+}
+
+TokenizedDataReader reader() const
+{
+	return TokenizedDataReader(impl, std::unordered_set<TokenId>{}, 0, 0);
+}
+
+/* Class TokenizedDataReader */
+
+TokenizedDataReaderFork TokenizedDataReader::fork()
+{
+	return TokenizedDataReaderFork(*this, impl, tokens, readCursor, peekCursor);
+}
+
+bool TokenizedDataReader::atEnd() const { return readCursor >= size(); }
+
+bool TokenizedData::read(Token &token, const TokenSet &tokens,
+                         WhitespaceMode mode)
+{
+	peekCursor = readCursor;
+	return impl->next(token, mode, tokens, readCursor);
+}
+
+bool TokenizedData::peek(Token &token, const TokenSet &tokens,
+                         WhitespaceMode mode)
+{
+	return impl->next(token, mode, tokens, peekCursor);
+}
+
+Variant TokenizedData::text(WhitespaceMode mode)
 {
 	// Copy the current cursor position to not update the actual cursor position
 	// if the operation was not successful
 	size_t cursorCopy = cursor;
+	Token token;
 	if (!impl->next(token, mode, tokens, cursorCopy) ||
 	    token.id != Tokens::Data) {
-		return false;
+		return Variant{nullptr};
 	}
 
-	// There is indeed a text token, update the internal cursor position
+	// There is indeed a text token, update the internal cursor position and
+	// return the token as variant.
 	cursor = cursorCopy;
-	return true;
+	Variant res = Variant::fromString(token.content);
+	res.setLocation(token.getLocation());
+	return res;
 }
 }
diff --git a/src/core/parser/utils/TokenizedData.hpp b/src/core/parser/utils/TokenizedData.hpp
index 38125c4..85b80ae 100644
--- a/src/core/parser/utils/TokenizedData.hpp
+++ b/src/core/parser/utils/TokenizedData.hpp
@@ -36,42 +36,29 @@
 #include <unordered_set>
 
 #include <core/common/Location.hpp>
+#include <core/common/Variant.hpp>
 #include <core/common/Whitespace.hpp>
-
-#include "Token.hpp"
+#include <core/common/Token.hpp>
 
 namespace ousia {
 
 // Forward declaration
 class TokenizedDataImpl;
+class TokenizedDataReader;
+class TokenizedDataReaderFork;
 
 /**
  * The TokenizedData class stores data extracted from a user defined document.
- * As users are capable of defining their own tokens and these are only valid
- * in certain scopes TokenizedData allows to divide the stored data into chunks
- * separated by tokens.
+ * The data stored in TokenizedData
  */
 class TokenizedData {
 private:
 	/**
-	 * Shared pointer pointing at the internal data. This data is shared when
-	 * copying TokenizedData instances, which corresponds to forking a
-	 * TokenizedData instance.
+	 * Shared pointer pointing at the internal data. This data is shared with
+	 * all the TokenizedDataReader instances.
 	 */
 	std::shared_ptr<TokenizedDataImpl> impl;
 
-	/**
-	 * Contains all currently enabled token ids.
-	 */
-	std::unordered_set<TokenId> tokens;
-
-	/**
-	 * Position from which the last element was read from the internal buffer.
-	 * This information is not shared with the other instances of TokenizedData
-	 * pointing at the same location.
-	 */
-	size_t cursor;
-
 public:
 	/**
 	 * Default constructor, creates a new instance of TokenizedData, sets the
@@ -136,25 +123,121 @@ public:
 	void mark(TokenId id, size_t bufStart, TokenLength len);
 
 	/**
-	 * Enables a single token id. Enabled tokens will no longer be returned as
-	 * text. Instead, when querying for the next token, TokenizedData will
-	 * return them as token and not as part of a Text token.
+	 * Resets the TokenizedData instance to the state it had when it was
+	 * constructred.
+	 */
+	void clear();
+
+	/**
+	 * Trims the length of the TokenizedData instance to the given length. Note
+	 * that this function does not remove any token matches for performance
+	 * reasons, it merely renders them incaccessible. Appending new data after
+	 * calling trim will make the token marks accessible again. Thus this method
+	 * should be the last function called to modify the data buffer and the
+	 * token marks.
 	 *
-	 * @param id is the TokenId of the token that should be enabled.
+	 * @param length is the number of characters to which the TokenizedData
+	 * instance should be trimmed.
 	 */
-	void enableToken(TokenId id) { tokens.insert(id); }
+	void trim(size_t length);
 
 	/**
-	 * Enables a set of token ids. Enabled tokens will no longer be returned as
-	 * text. Instead, when querying for the next token, TokenizedData will
-	 * return them as token and not as part of a Text token.
+	 * Returns the number of characters currently represented by this
+	 * TokenizedData instance.
+	 */
+	size_t size() const;
+
+	/**
+	 * Returns true if the TokenizedData instance is empty, false otherwise.
 	 *
-	 * @param ids is the TokenId of the token that should be enabled.
+	 * @return true if not data is stored inside the TokenizedData instance.
 	 */
-	void enableToken(const std::unordered_set<TokenId> &ids)
-	{
-		tokens.insert(ids.begin(), ids.end());
-	}
+	bool empty() const;
+
+	/**
+	 * Returns the location of the entire TokenizedData instance.
+	 *
+	 * @return the location of the entire data represented by this instance.
+	 */
+	SourceLocation getLocation() const;
+
+	/**
+	 * Returns a TokenizedDataReader instance that can be used to access the
+	 * data.
+	 *
+	 * @return a new TokenizedDataReader instance pointing at the beginning of
+	 * the internal buffer.
+	 */
+	TokenizedDataReader reader() const;
+};
+
+/**
+ * The TokenizedDataReader
+ */
+class TokenizedDataReader {
+private:
+	friend TokenizedData;
+
+	/**
+	 * Shared pointer pointing at the internal data. This data is shared with
+	 * all the TokenizedDataReader instances.
+	 */
+	std::shared_ptr<const TokenizedDataImpl> impl;
+
+	/**
+	 * Position from which the last element was read from the internal buffer.
+	 */
+	size_t readCursor;
+
+	/**
+	 * Position from which the last element was peeked from the internal buffer.
+	 */
+	size_t peekCursor;
+
+	/**
+	 * Private constructor of TokenizedDataReader, taking a reference to the
+	 * internal TokenizedDataImpl structure storing the data that is accessed by
+	 * the reader.
+	 *
+	 * @param impl is the TokenizedDataImpl instance that holds the actual data.
+	 * @param readCursor is the cursor position from which tokens and text are
+	 * read.
+	 * @param peekCursor is the cursor position from which tokens and text are
+	 * peeked.
+	 */
+	TokenizedDataReader(std::shared_ptr<TokenizedDataImpl> impl,
+	                    size_t readCursor, size_t peekCursor);
+
+public:
+	/**
+	 * Returns a new TokenizedDataReaderFork from which tokens and text can be
+	 * read without advancing this reader instance.
+	 */
+	TokenizedDataReaderFork fork();
+
+	/**
+	 * Returns true if this TokenizedData instance is at the end.
+	 *
+	 * @return true if the end of the TokenizedData instance has been reached.
+	 */
+	bool atEnd() const;
+
+	/**
+	 * Stores the next token in the given token reference, returns true if the
+	 * operation was successful, false if there are no more tokens. Advances the
+	 * internal cursor and re
+	 *
+	 * @param token is an output parameter into which the read token will be
+	 * stored. The TokenId is set to Tokens::Empty if there are no more tokens.
+	 * @param tokens is the set of token identifers, representing the currently
+	 * enabled tokens.
+	 * @param mode is the whitespace mode that should be used when a text token
+	 * is returned.
+	 * @return true if the operation was successful and there is a next token,
+	 * false if there are no more tokens.
+	 */
+	bool read(Token &token, const TokenSet &tokens = TokenSet{},
+	          WhitespaceMode mode = WhitespaceMode::COLLAPSE);
 
 	/**
 	 * Stores the next token in the given token reference, returns true if the
@@ -162,12 +245,26 @@ public:
 	 *
 	 * @param token is an output parameter into which the read token will be
 	 * stored. The TokenId is set to Tokens::Empty if there are no more tokens.
+	 * @param tokens is the set of token identifers, representing the currently
+	 * enabled tokens.
 	 * @param mode is the whitespace mode that should be used when a text token
 	 * is returned.
 	 * @return true if the operation was successful and there is a next token,
 	 * false if there are no more tokens.
 	 */
-	bool next(Token &token, WhitespaceMode mode = WhitespaceMode::COLLAPSE);
+	bool peek(Token &token, const TokenSet &tokens = TokenSet{},
+	          WhitespaceMode mode = WhitespaceMode::COLLAPSE);
+
+	/**
+	 * Consumes the peeked tokens, the read cursor will now be at the position
+	 * of the peek cursor.
+	 */
+	void consumePeek() { readCursor = peekCursor; }
+
+	/**
+	 * Resets the peek cursor to the position of the read cursor.
+	 */
+	void resetPeek() { peekCursor = readCursor; }
 
 	/**
 	 * Stores the next text token in the given token reference, returns true if
@@ -178,12 +275,53 @@ public:
 	 * stored. The TokenId is set to Tokens::Empty if there are no more tokens.
 	 * @param mode is the whitespace mode that should be used when a text token
 	 * is returned.
-	 * @return true if the operation was successful and there is a next token,
-	 * false if there are no more tokens.
+	 * @return a string variant with the data if there is any data or a nullptr
+	 * variant if there is no text.
 	 */
-	bool text(Token &token, WhitespaceMode mode = WhitespaceMode::COLLAPSE);
+	Variant text(WhitespaceMode mode = WhitespaceMode::COLLAPSE);
 };
+
+/**
+ * The TokenizedDataReaderFork class is created when forking a
+ * TokenizedDataReader
+ */
+class TokenizedDataReaderFork : public TokenizedDataReader {
+private:
+	friend TokenizedDataReader;
+
+	/**
+	 * Reference pointing at the parent TokenizedDataReader to which changes may
+	 * be commited.
+	 */
+	TokenizedDataReader &parent;
+
+	/**
+	 * Private constructor of TokenizedDataReaderFork, taking a reference to the
+	 * internal TokenizedDataImpl structure storing the data that is accessed by
+	 * the reader and a reference at the parent TokenizedDataReader.
+	 *
+	 * @param parent is the TokenizedDataReader instance to which the current
+	 * read/peek progress may be commited.
+	 * @param impl is the TokenizedDataImpl instance that holds the actual data.
+	 * @param readCursor is the cursor position from which tokens and text are
+	 * read.
+	 * @param peekCursor is the cursor position from which tokens and text are
+	 * peeked.
+	 */
+	TokenizedDataReaderFork(TokenizedDataReader &parent,
+	                        std::shared_ptr<TokenizedDataImpl> impl,
+	                        size_t readCursor, size_t peekCursor)
+	    : TokenizedDataReader(impl, readCursor, peekCursor), parent(parent)
+	{
+	}
+
+public:
+	/**
+	 * Commits the read/peek progress to the underlying parent.
+	 */
+	void commit() { parent = *this; }
+}
 }
 
-#endif /* _OUSIA_DYNAMIC_TOKENIZER_HPP_ */
+#endif /* _OUSIA_TOKENIZED_DATA_HPP_ */
 
diff --git a/src/core/parser/utils/Tokenizer.cpp b/src/core/parser/utils/Tokenizer.cpp
index 2e0ac13..51787cd 100644
--- a/src/core/parser/utils/Tokenizer.cpp
+++ b/src/core/parser/utils/Tokenizer.cpp
@@ -22,8 +22,8 @@
 #include <core/common/CharReader.hpp>
 #include <core/common/Exceptions.hpp>
 #include <core/common/Utils.hpp>
-#include <core/common/WhitespaceHandler.hpp>
 
+#include "TokenizedData.hpp"
 #include "Tokenizer.hpp"
 
 namespace ousia {
@@ -42,26 +42,33 @@ struct TokenMatch {
 	Token token;
 
 	/**
-	 * Current length of the data within the text handler. The text buffer needs
-	 * to be trimmed to this length if this token matches.
+	 * Position at which this token starts in the TokenizedData instance.
 	 */
-	size_t textLength;
+	size_t dataStartOffset;
 
 	/**
-	 * End location of the current text handler. This location needs to be used
-	 * for the text token that is emitted before the actual token.
+	 * Set to true if the matched token is a primary token.
 	 */
-	size_t textEnd;
+	bool primary;
 
 	/**
 	 * Constructor of the TokenMatch class.
 	 */
-	TokenMatch() : textLength(0), textEnd(0) {}
+	TokenMatch() : dataStartOffset(0), primary(false) {}
 
 	/**
 	 * Returns true if this TokenMatch instance actually represents a match.
+	 *
+	 * @return true if the TokenMatch actually has a match.
+	 */
+	bool hasMatch() const { return token.id != Tokens::Empty; }
+
+	/**
+	 * Returns the length of the matched token.
+	 *
+	 * @return the length of the token string.
 	 */
-	bool hasMatch() { return token.id != Tokens::Empty; }
+	size_t size() const { return token.content.size(); }
 };
 
 /* Internal class TokenLookup */
@@ -83,36 +90,28 @@ private:
 	size_t start;
 
 	/**
-	 * Current length of the data within the text handler. The text buffer needs
-	 * to be trimmed to this length if this token matches.
+	 * Position at which this token starts in the TokenizedData instance.
 	 */
-	size_t textLength;
-
-	/**
-	 * End location of the current text handler. This location needs to be used
-	 * for the text token that is emitted before the actual token.
-	 */
-	size_t textEnd;
+	size_t dataStartOffset;
 
 public:
 	/**
 	 * Constructor of the TokenLookup class.
 	 *
 	 * @param node is the current node.
-	 * @param start is the start position.
-	 * @param textLength is the text buffer length of the previous text token.
-	 * @param textEnd is the current end location of the previous text token.
+	 * @param start is the start position in the source file.
+	 * @param dataStartOffset is the current length of the TokenizedData buffer.
 	 */
-	TokenLookup(const TokenTrie::Node *node, size_t start, size_t textLength,
-	            size_t textEnd)
-	    : node(node), start(start), textLength(textLength), textEnd(textEnd)
+	TokenLookup(const TokenTrie::Node *node, size_t start,
+	            size_t dataStartOffset)
+	    : node(node), start(start), dataStartOffset(dataStartOffset)
 	{
 	}
 
 	/**
 	 * Tries to extend the current path in the token trie with the given
-	 * character. If a complete token is matched, stores this match in the
-	 * tokens list (in case it is longer than any previous token).
+	 * character. If a complete token is matched, stores the match in the given
+	 * TokenMatch reference and returns true.
 	 *
 	 * @param c is the character that should be appended to the current prefix.
 	 * @param lookups is a list to which new TokeLookup instances are added --
@@ -123,73 +122,48 @@ public:
 	 * Tokenizer.
 	 * @param end is the end byte offset of the current character.
 	 * @param sourceId is the source if of this file.
+	 * @return true if a token was matched, false otherwise.
 	 */
-	void advance(char c, std::vector<TokenLookup> &lookups, TokenMatch &match,
-	             const std::vector<std::string> &tokens, SourceOffset end,
-	             SourceId sourceId)
+	bool advance(char c, std::vector<TokenLookup> &lookups, TokenMatch &match,
+	             const std::vector<Tokenizer::TokenDescriptor> &tokens,
+	             SourceOffset end, SourceId sourceId)
 	{
-		// Check whether we can continue the current token path with the given
-		// character without visiting an already visited node
+		// Set to true once a token has been matched
+		bool res = false;
+
+		// Check whether we can continue the current token path, if not, abort
 		auto it = node->children.find(c);
 		if (it == node->children.end()) {
-			return;
+			return res;
 		}
 
 		// Check whether the new node represents a complete token a whether it
 		// is longer than the current token. If yes, replace the current token.
 		node = it->second.get();
-		if (node->type != Tokens::Empty) {
-			const std::string &str = tokens[node->type];
-			size_t len = str.size();
-			if (len > match.token.content.size()) {
-				match.token =
-				    Token{node->type, str, {sourceId, start, end}};
-				match.textLength = textLength;
-				match.textEnd = textEnd;
-			}
+		if (node->id != Tokens::Empty) {
+			const Tokenizer::TokenDescriptor &descr = tokens[node->id];
+			match.token = Token(node->id, descr.string,
+			                    SourceLocation(sourceId, start, end));
+			match.dataStartOffset = dataStartOffset;
+			match.primary = descr.primary;
+			res = true;
 		}
 
 		// If this state can possibly be advanced, store it in the states list.
 		if (!node->children.empty()) {
 			lookups.emplace_back(*this);
 		}
+		return res;
 	}
 };
-
-/**
- * Transforms the given token into a data token containing the extracted
- * text.
- *
- * @param handler is the WhitespaceHandler containing the collected data.
- * @param token is the output token to which the text should be written.
- * @param sourceId is the source id of the underlying file.
- */
-static void buildDataToken(const WhitespaceHandler &handler, TokenMatch &match,
-                           SourceId sourceId)
-{
-	if (match.hasMatch()) {
-		match.token.content =
-		    std::string{handler.textBuf.data(), match.textLength};
-		match.token.location =
-		    SourceLocation{sourceId, handler.textStart, match.textEnd};
-	} else {
-		match.token.content = handler.toString();
-		match.token.location =
-		    SourceLocation{sourceId, handler.textStart, handler.textEnd};
-	}
-	match.token.id = Tokens::Data;
-}
 }
 
 /* Class Tokenizer */
 
-Tokenizer::Tokenizer(WhitespaceMode whitespaceMode)
-    : whitespaceMode(whitespaceMode), nextTokenId(0)
-{
-}
+Tokenizer::Tokenizer() : nextTokenId(0) {}
 
-template <typename TextHandler, bool read>
-bool Tokenizer::next(CharReader &reader, Token &token)
+template <bool read>
+bool Tokenizer::next(CharReader &reader, Token &token, TokenizedData &data)
 {
 	// If we're in the read mode, reset the char reader peek position to the
 	// current read position
@@ -199,43 +173,68 @@ bool Tokenizer::next(CharReader &reader, Token &token)
 
 	// Prepare the lookups in the token trie
 	const TokenTrie::Node *root = trie.getRoot();
-	TokenMatch match;
+	TokenMatch bestMatch;
 	std::vector<TokenLookup> lookups;
 	std::vector<TokenLookup> nextLookups;
 
-	// Instantiate the text handler
-	TextHandler textHandler;
-
 	// Peek characters from the reader and try to advance the current token tree
 	// cursor
 	char c;
+	const size_t initialDataSize = data.size();
 	size_t charStart = reader.getPeekOffset();
 	const SourceId sourceId = reader.getSourceId();
 	while (reader.peek(c)) {
 		const size_t charEnd = reader.getPeekOffset();
-		const size_t textLength = textHandler.textBuf.size();
-		const size_t textEnd = textHandler.textEnd;
+		const size_t dataStartOffset = data.size();
 
 		// If we do not have a match yet, start a new lookup from the root
-		if (!match.hasMatch()) {
-			TokenLookup{root, charStart, textLength, textEnd}.advance(
-			    c, nextLookups, match, tokens, charEnd, sourceId);
+		if (!bestMatch.hasMatch()) {
+			lookups.emplace_back(root, charStart, dataStartOffset);
 		}
 
 		// Try to advance all other lookups with the new character
+		TokenMatch match;
 		for (TokenLookup &lookup : lookups) {
-			lookup.advance(c, nextLookups, match, tokens, charEnd, sourceId);
+			// Continue if the current lookup
+			if (!lookup.advance(c, nextLookups, match, tokens, charEnd,
+			                    sourceId)) {
+				continue;
+			}
+
+			// If the matched token is primary, check whether it is better than
+			// the current best match, if yes, replace the best match. In any
+			// case just continue
+			if (match.primary) {
+				if (match.size() > bestMatch.size()) {
+					bestMatch = match;
+				}
+				continue;
+			}
+
+			// Otherwise -- if the matched token is a non-primary token (and no
+			// primary token has been found until now) -- mark the match in the
+			// TokenizedData
+			if (!bestMatch.hasMatch()) {
+				data.mark(match.token.id, data.size() - match.size() + 1,
+				          match.size());
+			}
 		}
 
 		// We have found a token and there are no more states to advance or the
 		// text handler has found something -- abort to return the new token
-		if (match.hasMatch()) {
-			if ((nextLookups.empty() || textHandler.hasText())) {
+		if (bestMatch.hasMatch()) {
+			if ((nextLookups.empty() || data.size() > initialDataSize)) {
 				break;
 			}
 		} else {
 			// Record all incomming characters
-			textHandler.append(c, charStart, charEnd);
+			data.append(c, charStart, charEnd);
+
+			// Special token processing
+			// TODO: Build a special state machine for this in another class
+			if (c == '\n') {
+				data.mark(Tokens::Newline, 1);
+			}
 		}
 
 		// Swap the lookups and the nextLookups list
@@ -246,60 +245,53 @@ bool Tokenizer::next(CharReader &reader, Token &token)
 		charStart = charEnd;
 	}
 
-	// If we found text, emit that text
-	if (textHandler.hasText() && (!match.hasMatch() || match.textLength > 0)) {
-		buildDataToken(textHandler, match, sourceId);
+	// If we found data, emit a corresponding data token
+	if (data.size() > initialDataSize &&
+	    (!bestMatch.hasMatch() ||
+	     bestMatch.dataStartOffset > initialDataSize)) {
+		// If we have a "bestMatch" wich starts after text data has started,
+		// trim the TokenizedData to this offset
+		if (bestMatch.dataStartOffset > initialDataSize) {
+			data.trim(bestMatch.dataStartOffset);
+		}
+
+		// Create a token containing the data location
+		bestMatch.token = Token{data.getLocation()};
 	}
 
 	// Move the read/peek cursor to the end of the token, abort if an error
 	// happens while doing so
-	if (match.hasMatch()) {
+	if (bestMatch.hasMatch()) {
 		// Make sure we have a valid location
-		if (match.token.location.getEnd() == InvalidSourceOffset) {
+		if (bestMatch.token.location.getEnd() == InvalidSourceOffset) {
 			throw OusiaException{"Token end position offset out of range"};
 		}
 
 		// Seek to the end of the current token
-		const size_t end = match.token.location.getEnd();
+		const size_t end = bestMatch.token.location.getEnd();
 		if (read) {
 			reader.seek(end);
 		} else {
 			reader.seekPeekCursor(end);
 		}
-		token = match.token;
+		token = bestMatch.token;
 	} else {
 		token = Token{};
 	}
-	return match.hasMatch();
+	return bestMatch.hasMatch();
 }
 
-bool Tokenizer::read(CharReader &reader, Token &token)
+bool Tokenizer::read(CharReader &reader, Token &token, TokenizedData &data)
 {
-	switch (whitespaceMode) {
-		case WhitespaceMode::PRESERVE:
-			return next<PreservingWhitespaceHandler, true>(reader, token);
-		case WhitespaceMode::TRIM:
-			return next<TrimmingWhitespaceHandler, true>(reader, token);
-		case WhitespaceMode::COLLAPSE:
-			return next<CollapsingWhitespaceHandler, true>(reader, token);
-	}
-	return false;
+	return next<true>(reader, token, data);
 }
 
-bool Tokenizer::peek(CharReader &reader, Token &token)
+bool Tokenizer::peek(CharReader &reader, Token &token, TokenizedData &data)
 {
-	switch (whitespaceMode) {
-		case WhitespaceMode::PRESERVE:
-			return next<PreservingWhitespaceHandler, false>(reader, token);
-		case WhitespaceMode::TRIM:
-			return next<TrimmingWhitespaceHandler, false>(reader, token);
-		case WhitespaceMode::COLLAPSE:
-			return next<CollapsingWhitespaceHandler, false>(reader, token);
-	}
-	return false;
+	return next<false>(reader, token, data);
 }
 
-TokenId Tokenizer::registerToken(const std::string &token)
+TokenId Tokenizer::registerToken(const std::string &token, bool primary)
 {
 	// Abort if an empty token should be registered
 	if (token.empty()) {
@@ -309,8 +301,8 @@ TokenId Tokenizer::registerToken(const std::string &token)
 	// Search for a new slot in the tokens list
 	TokenId type = Tokens::Empty;
 	for (size_t i = nextTokenId; i < tokens.size(); i++) {
-		if (tokens[i].empty()) {
-			tokens[i] = token;
+		if (!tokens[i].valid()) {
+			tokens[i] = TokenDescriptor(token, primary);
 			type = i;
 			break;
 		}
@@ -320,62 +312,47 @@ TokenId Tokenizer::registerToken(const std::string &token)
 	// override the special token type handles
 	if (type == Tokens::Empty) {
 		type = tokens.size();
-		if (type == Tokens::Data || type == Tokens::Empty) {
+		if (type >= Tokens::MaxTokenId) {
 			throw OusiaException{"Token type ids depleted!"};
 		}
-		tokens.emplace_back(token);
+		tokens.emplace_back(token, primary);
 	}
 	nextTokenId = type + 1;
 
-	// Try to register the token in the trie -- if this fails, remove it
-	// from the tokens list
+	// Try to register the token in the trie -- if this fails, remove it from
+	// the tokens list
 	if (!trie.registerToken(token, type)) {
-		tokens[type] = std::string{};
+		tokens[type] = TokenDescriptor();
 		nextTokenId = type;
 		return Tokens::Empty;
 	}
 	return type;
 }
 
-bool Tokenizer::unregisterToken(TokenId type)
+bool Tokenizer::unregisterToken(TokenId id)
 {
 	// Unregister the token from the trie, abort if an invalid type is given
-	if (type < tokens.size() && trie.unregisterToken(tokens[type])) {
-		tokens[type] = std::string{};
-		nextTokenId = type;
+	if (id < tokens.size() && trie.unregisterToken(tokens[id].string)) {
+		tokens[id] = TokenDescriptor();
+		nextTokenId = id;
 		return true;
 	}
 	return false;
 }
 
-std::string Tokenizer::getTokenString(TokenId type)
-{
-	if (type < tokens.size()) {
-		return tokens[type];
-	}
-	return std::string{};
-}
+static Tokenizer::TokenDescriptor EmptyTokenDescriptor;
 
-void Tokenizer::setWhitespaceMode(WhitespaceMode mode)
+const Tokenizer::TokenDescriptor &Tokenizer::lookupToken(TokenId id) const
 {
-	whitespaceMode = mode;
+	if (id < tokens.size()) {
+		return tokens[id];
+	}
+	return EmptyTokenDescriptor;
 }
 
-WhitespaceMode Tokenizer::getWhitespaceMode() { return whitespaceMode; }
-
 /* Explicitly instantiate all possible instantiations of the "next" member
    function */
-template bool Tokenizer::next<PreservingWhitespaceHandler, false>(
-    CharReader &reader, Token &token);
-template bool Tokenizer::next<TrimmingWhitespaceHandler, false>(
-    CharReader &reader, Token &token);
-template bool Tokenizer::next<CollapsingWhitespaceHandler, false>(
-    CharReader &reader, Token &token);
-template bool Tokenizer::next<PreservingWhitespaceHandler, true>(
-    CharReader &reader, Token &token);
-template bool Tokenizer::next<TrimmingWhitespaceHandler, true>(
-    CharReader &reader, Token &token);
-template bool Tokenizer::next<CollapsingWhitespaceHandler, true>(
-    CharReader &reader, Token &token);
+template bool Tokenizer::next<false>(CharReader &, Token &, TokenizedData &);
+template bool Tokenizer::next<true>(CharReader &, Token &, TokenizedData &);
 }
 
diff --git a/src/core/parser/utils/Tokenizer.hpp b/src/core/parser/utils/Tokenizer.hpp
index f21c6a3..2ddb9c9 100644
--- a/src/core/parser/utils/Tokenizer.hpp
+++ b/src/core/parser/utils/Tokenizer.hpp
@@ -19,8 +19,8 @@
 /**
  * @file Tokenizer.hpp
  *
- * Tokenizer that can be reconfigured at runtime used for parsing the plain
- * text format.
+ * Tokenizer that can be reconfigured at runtime and is used for parsing the
+ * plain text format.
  *
  * @author Andreas Stöckel (astoecke@techfak.uni-bielefeld.de)
  */
@@ -33,39 +33,75 @@
 #include <vector>
 
 #include <core/common/Location.hpp>
-#include <core/common/Whitespace.hpp>
+#include <core/common/Token.hpp>
 
-#include "Token.hpp"
 #include "TokenTrie.hpp"
 
 namespace ousia {
 
 // Forward declarations
 class CharReader;
+class TokenizedData;
 
 /**
  * The Tokenizer is used to extract tokens and chunks of text from a
- * CharReader. It allows to register and unregister tokens while parsing and
- * to modify the handling of whitespace characters. Note that the
- * Tokenizer always tries to extract the longest possible token from the
- * tokenizer.
+ * CharReader. It allows to register and unregister tokens while parsing. Note
+ * that the Tokenizer always tries to extract the longest possible token from
+ * the tokenizer. Tokens can be registered as primary or non-primary token. If
+ * a Token is registered as a primary token, it is returned as a single Token
+ * instance if it occurs. In the non-primary case the token is returned as part
+ * of a segmented TokenizedData instance.
  */
 class Tokenizer {
-private:
+public:
 	/**
-	 * Internally used token trie. This object holds all registered tokens.
+	 * Internally used structure describing a registered token.
 	 */
-	TokenTrie trie;
+	struct TokenDescriptor {
+		/**
+		 * String describing the token.
+		 */
+		std::string string;
+
+		/**
+		 * Set to true if this token is primary.
+		 */
+		bool primary;
+
+		/**
+		 * Constructor of the TokenDescriptor class.
+		 *
+		 * @param string is the string representation of the registered token.
+		 * @param primary specifies whether the token is a primary token that
+		 * should be returned as a single token, or a secondary token, that
+		 * should be returned as part of TokenizedData.
+		 */
+		TokenDescriptor(const std::string &string, bool primary)
+		    : string(string), primary(primary)
+		{
+		}
+
+		/**
+		 * Default constructor.
+		 */
+		TokenDescriptor() : primary(false) {}
+
+		/**
+		 * Returns true if the TokenDescriptor represents a valid token.
+		 */
+		bool valid() { return !string.empty(); }
+	};
 
+private:
 	/**
-	 * Flag defining whether whitespaces should be preserved or not.
+	 * Internally used token trie. This object holds all registered tokens.
 	 */
-	WhitespaceMode whitespaceMode;
+	TokenTrie trie;
 
 	/**
 	 * Vector containing all registered token types.
 	 */
-	std::vector<std::string> tokens;
+	std::vector<TokenDescriptor> tokens;
 
 	/**
 	 * Next index in the tokens list where to search for a new token id.
@@ -74,90 +110,78 @@ private:
 
 	/**
 	 * Templated function used internally to read the current token. The
-	 * function is templated in order to force code generation for all six
-	 * combiations of whitespace modes and reading/peeking.
+	 * function is templated in order to force optimized code generation for
+	 * both reading and peeking.
 	 *
-	 * @tparam TextHandler is the type to be used for the textHandler instance.
-	 * @tparam read specifies whether the function should start from and advance
-	 * the read pointer of the char reader.
+	 * @tparam read specifies whether the method should read the token or just
+	 * peek.
 	 * @param reader is the CharReader instance from which the data should be
 	 * read.
 	 * @param token is the token structure into which the token information
 	 * should be written.
+	 * @param data is a reference at the TokenizedData instance to which the
+	 * token information should be appended.
 	 * @return false if the end of the stream has been reached, true otherwise.
 	 */
-	template <typename TextHandler, bool read>
-	bool next(CharReader &reader, Token &token);
+	template <bool read>
+	bool next(CharReader &reader, Token &token, TokenizedData &data);
 
 public:
 	/**
 	 * Constructor of the Tokenizer class.
-	 *
-	 * @param whitespaceMode specifies how whitespace should be handled.
 	 */
-	Tokenizer(WhitespaceMode whitespaceMode = WhitespaceMode::COLLAPSE);
+	Tokenizer();
 
 	/**
-	 * Registers the given string as a token. Returns a const pointer at a
-	 * TokenDescriptor that will be used to reference the newly created token.
+	 * Registers the given string as a token. Returns a unique identifier
+	 * describing the registered token.
 	 *
 	 * @param token is the token string that should be registered.
-	 * @return a unique identifier for the registered token or EmptyToken if
+	 * @param primary specifies whether the token is a primary token -- if true,
+	 * the token will be returned as a single, standalone token. Otherwise the
+	 * token will be returned as part of a "TokenizedData" structure.
+	 * @return a unique identifier for the registered token or Tokens::Empty if
 	 * an error occured.
 	 */
-	TokenId registerToken(const std::string &token);
+	TokenId registerToken(const std::string &token, bool primary = true);
 
 	/**
 	 * Unregisters the token belonging to the given TokenId.
 	 *
 	 * @param type is the token type that should be unregistered. The
-	 *TokenId
-	 * must have been returned by registerToken.
+	 * TokenId must have been returned by registerToken.
 	 * @return true if the operation was successful, false otherwise (e.g.
-	 * because the given TokenDescriptor was already unregistered).
+	 * because the token with the given TokenId was already unregistered).
 	 */
-	bool unregisterToken(TokenId type);
+	bool unregisterToken(TokenId id);
 
 	/**
 	 * Returns the token that was registered under the given TokenId id or
-	 *an
-	 * empty string if an invalid TokenId id is given.
+	 * an empty string if an invalid TokenId id is given.
 	 *
-	 * @param type is the TokenId id for which the corresponding token
-	 *string
+	 * @param id is the TokenId for which the corresponding TokenDescriptor
 	 * should be returned.
-	 * @return the registered token string or an empty string if the given type
-	 * was invalid.
-	 */
-	std::string getTokenString(TokenId type);
-
-	/**
-	 * Sets the whitespace mode.
-	 *
-	 * @param whitespaceMode defines how whitespace should be treated in text
-	 * tokens.
-	 */
-	void setWhitespaceMode(WhitespaceMode mode);
-
-	/**
-	 * Returns the current value of the whitespace mode.
-	 *
-	 * @return the whitespace mode.
+	 * @return the registered TokenDescriptor or an invalid TokenDescriptor if
+	 * the given TokenId is invalid.
 	 */
-	WhitespaceMode getWhitespaceMode();
+	const TokenDescriptor& lookupToken(TokenId id) const;
 
 	/**
 	 * Reads a new token from the CharReader and stores it in the given
-	 * Token instance.
+	 * Token instance. If the token has the id Tokens::Data, use the "getData"
+	 * method to fetch a reference at the underlying TokenizedData instance
+	 * storing the data.
 	 *
 	 * @param reader is the CharReader instance from which the data should be
 	 * read.
 	 * @param token is a reference at the token instance into which the Token
 	 * information should be written.
+	 * @param data is a reference at the TokenizedData instance to which the
+	 * token information should be appended.
 	 * @return true if a token could be read, false if the end of the stream
 	 * has been reached.
 	 */
-	bool read(CharReader &reader, Token &token);
+	bool read(CharReader &reader, Token &token, TokenizedData &data);
 
 	/**
 	 * The peek method does not advance the read position of the char reader,
@@ -167,10 +191,12 @@ public:
 	 * read.
 	 * @param token is a reference at the token instance into which the Token
 	 * information should be written.
+	 * @param data is a reference at the TokenizedData instance to which the
+	 * token information should be appended.
 	 * @return true if a token could be read, false if the end of the stream
 	 * has been reached.
 	 */
-	bool peek(CharReader &reader, Token &token);
+	bool peek(CharReader &reader, Token &token, TokenizedData &data);
 };
 }