Merge branch 'master' of somweyr.de:ousia

13 files changed, 645 insertions, 220 deletions

diff --git a/src/core/Registry.cpp b/src/core/Registry.cpp
index 74d1cf8..9427aed 100644
--- a/src/core/Registry.cpp
+++ b/src/core/Registry.cpp
@@ -16,8 +16,11 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <core/common/Logger.hpp>
 #include <core/parser/Parser.hpp>
+#include <core/resource/Resource.hpp>
+#include <core/resource/ResourceLocator.hpp>
+
+#include "Registry.hpp"
 
 namespace ousia {
 
@@ -25,13 +28,13 @@ using namespace parser;
 
 /* Class Registry */
 
-void Registry::registerParser(parser::Parser *parser)
+void Registry::registerParser(parser::Parser &parser)
 {
-	parsers.push_back(parser);
-	for (const auto &mime : parser->mimetypes()) {
+	parsers.push_back(&parser);
+	for (const auto &mime : parser.mimetypes()) {
 		//TODO: This does not allow for multiple parsers with the same mimetype.
 		// Is that how its supposed to be?
-		parserMimetypes.insert(std::make_pair(mime, parser));
+		parserMimetypes.insert(std::make_pair(mime, &parser));
 	}
 }
 
@@ -44,24 +47,40 @@ Parser *Registry::getParserForMimetype(const std::string &mimetype) const
 	return nullptr;
 }
 
-void Registry::registerResourceLocator(ResourceLocator *locator)
+void Registry::registerResourceLocator(ResourceLocator &locator)
 {
-	locators.push_back(locator);
+	locators.push_back(&locator);
 }
 
-ResourceLocator::Location Registry::locateResource(
-    const std::string &path, const std::string &relativeTo,
-    ResourceLocator::Type type) const
+bool Registry::locateResource(Resource &resource, const std::string &path,
+                              ResourceType type,
+                              const Resource &relativeTo) const
 {
-	ResourceLocator::Location *last;
+	// Try the locator of the given "relativeTo" resource first
+	if (relativeTo.isValid()) {
+		if (relativeTo.getLocator().locate(resource, path, type, relativeTo)) {
+			return true;
+		}
+	}
+
+	// Iterate over all registered locators and try to resolve the given path
 	for (auto &locator : locators) {
-		ResourceLocator::Location loc = locator->locate(path, relativeTo, type);
-		if (loc.found) {
-			return loc;
+		if (locator->locate(resource, path, type, relativeTo)) {
+			return true;
 		}
-		last = &loc;
 	}
-	return *last;
+
+	// If this did not work out, retry but use the UNKNOWN type.
+	if (type != ResourceType::UNKNOWN) {
+		for (auto &locator : locators) {
+			if (locator->locate(resource, path, ResourceType::UNKNOWN,
+			                    relativeTo)) {
+				return true;
+			}
+		}
+	}
+
+	return false;
 }
 }
 
diff --git a/src/core/Registry.hpp b/src/core/Registry.hpp
index 01d57e8..40eede1 100644
--- a/src/core/Registry.hpp
+++ b/src/core/Registry.hpp
@@ -22,37 +22,34 @@
 #include <map>
 #include <vector>
 
-#include "ResourceLocator.hpp"
+#include <core/resource/Resource.hpp>
 
 namespace ousia {
 
 // TODO: Add support for ScriptEngine type
 
-class Logger;
-
 namespace parser {
 class Parser;
 }
+class ResourceLocator;
 
 class Registry {
 private:
-	Logger &logger;
 	std::vector<parser::Parser *> parsers;
 	std::map<std::string, parser::Parser *> parserMimetypes;
+
 	std::vector<ResourceLocator *> locators;
 
 public:
-	Registry(Logger &logger) : logger(logger) {}
-
-	void registerParser(parser::Parser *parser);
+	void registerParser(parser::Parser &parser);
 
-	parser::Parser *getParserForMimetype(const std::string& mimetype) const;
+	parser::Parser *getParserForMimetype(const std::string &mimetype) const;
 
-	void registerResourceLocator(ResourceLocator *locator);
+	void registerResourceLocator(ResourceLocator &locator);
 
-	ResourceLocator::Location locateResource(const std::string &path,
-	                                         const std::string &relativeTo,
-	                                         ResourceLocator::Type type) const;
+	bool locateResource(Resource &resource, const std::string &path,
+	                    ResourceType type = ResourceType::UNKNOWN,
+	                    const Resource &relativeTo = NullResource) const;
 };
 }
 
diff --git a/src/core/ResourceLocator.hpp b/src/core/ResourceLocator.hpp
deleted file mode 100644
index 39c7b30..0000000
--- a/src/core/ResourceLocator.hpp
+++ /dev/null
@@ -1,129 +0,0 @@
-/*
-    Ousía
-    Copyright (C) 2014, 2015  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/>.
-*/
-
-#ifndef _OUSIA_RESOURCE_LOCATOR_HPP_
-#define _OUSIA_RESOURCE_LOCATOR_HPP_
-
-#include <istream>
-#include <memory>
-
-namespace ousia {
-
-/**
- * A ResourceLocator is a class able to locate resources in some way, usually
- * on the hard drive.
- *
- * We specify this as an abstract superclass to have an interface layer between
- * the program core and possible future extensions in terms of resource
- * locations (e.g. online resources, .zip files, etc.).
- */
-class ResourceLocator {
-public:
-	/**
-	 * This enum contains all possible types of includable resources in Ousía.
-	 */
-	enum class Type {
-		// A Domain description
-		DOMAIN_DESC,
-		// An ECMA/JavaScript
-		SCRIPT,
-		// A Type System
-		TYPESYS,
-		DOCUMENT,
-		ATTRIBUTES,
-		// TODO: Aren't documents and attribute descriptors missing?
-		// TODO: What is the purpose of these two?
-		GENERIC_MODULE,
-		GENERIC_INCLUDE
-	};
-
-	/**
-	 * A Location contains the location of a Resource, e.g. a file path
-	 * on a hard drive. Note that the 'found' flag might be set to false
-	 * indicating that a resource was not found.
-	 */
-	struct Location {
-		const bool found;
-		const ResourceLocator &locator;
-		const Type type;
-		/**
-		 * This is a fully qualified/canonical path to the resource found or
-		 * in an undefined state (possibly empty) if the 'found' flag is set
-		 * to 'false'.
-		 */
-		const std::string location;
-
-		Location(const bool found, const ResourceLocator &locator,
-		         const Type type, const std::string location)
-		    : found(found), locator(locator), type(type), location(location)
-		{
-		}
-
-		/**
-		 * This calls the 'stream' method of the underlying ResourceLocator that
-		 * found this location and returns a stream containing the data of the
-		 * Resource at this location.
-		 *
-		 * @return a stream containing the data of the Resource at this
-		 *         location. This has to be a unique_pointer because the current
-		 *         C++11 compiler does not yet support move semantics for
-		 *         streams.
-		 */
-		std::unique_ptr<std::istream> stream() const
-		{
-			return std::move(locator.stream(location));
-		}
-	};
-
-	/**
-	 * The locate function uses this ResourceLocator to search for a given
-	 * Resource name (path parameter). It returns a Location with the
-	 * 'found' flag set accordingly.
-	 *
-	 * @param path is the resource name.
-	 * @param relativeTo is an already resolved fully qualified name/canonical
-	 *                   path that is to be used as base directory for this
-	 *                   search.
-	 * @param type is the type of this resource.
-	 *
-	 * @return A Location containing either the found location of the
-	 *         Resource and the found flag set to 'true' or an empty location
-	 *         and the found flag set to 'false'.
-	 */
-	virtual Location locate(const std::string &path,
-	                        const std::string &relativeTo,
-	                        const Type type) const = 0;
-
-	/**
-	 * This method returns a strem containing the data of the resource at the
-	 * given location.
-	 *
-	 * @param location is a found location, most likely from a Location.
-	 *
-	 * @return a stream containing the data of the Resource at this
-	 *         location. This has to be a unique_pointer because the current
-	 *         C++11 compiler does not yet support move semantics for
-	 *         streams.
-	 */
-	virtual std::unique_ptr<std::istream> stream(
-	    const std::string &location) const = 0;
-};
-}
-
-#endif /* _RESOURCE_LOCATOR_HPP_ */
-
diff --git a/src/core/model/Project.cpp b/src/core/model/Project.cpp
index c491d4f..fc08660 100644
--- a/src/core/model/Project.cpp
+++ b/src/core/model/Project.cpp
@@ -100,6 +100,7 @@ const Rtti Project = RttiBuilder<model::Project>("Project")
                          .parent(&Node)
                          .composedOf(&Document)
                          .composedOf(&Typesystem)
+                         .composedOf(&SystemTypesystem)
                          .composedOf(&Domain);
 }
 }
diff --git a/src/core/parser/Scope.cpp b/src/core/parser/Scope.cpp
index 6942b9a..01292df 100644
--- a/src/core/parser/Scope.cpp
+++ b/src/core/parser/Scope.cpp
@@ -119,7 +119,7 @@ Rooted<Node> Scope::getLeaf() { return nodes.back(); }
 bool Scope::resolve(const std::vector<std::string> &path, const Rtti &type,
                     Logger &logger, ResolutionImposterCallback imposterCallback,
                     ResolutionResultCallback resultCallback,
-	             const SourceLocation &location)
+                    const SourceLocation &location)
 {
 	if (!resolve(path, type, logger, resultCallback, location)) {
 		resultCallback(imposterCallback(), logger);
@@ -168,22 +168,21 @@ bool Scope::performDeferredResolution(Logger &logger)
 		}
 	}
 
-	// Output an error message if there are still deferred elements left that
-	// could not be resolved
-	if (!deferred.empty()) {
-		for (const auto &failed : deferred) {
-			logger.error(
-			    std::string("Could not resolve a reference to \"") +
-			        Utils::join(failed.path, ".") +
-			        std::string("\" of type " + failed.type.name),
-			    failed.location);
-		}
+	// We were successful if there are no more deferred resolutions
+	if (deferred.empty()) {
+		return true;
 	}
 
-	// We were successful if there are no more deferred resolutions
-	return deferred.empty();
+	// Output error messages for all elements for which resolution did not
+	// succeed.
+	for (const auto &failed : deferred) {
+		logger.error(std::string("Could not resolve ")  + failed.type.name + std::string(" \"") +
+		                 Utils::join(failed.path, ".") +
+		                 std::string("\""),
+		             failed.location);
+	}
+	deferred.clear();
+	return false;
 }
-
-void Scope::purgeDeferredResolutions() { deferred.clear(); }
 }
 }
diff --git a/src/core/parser/Scope.hpp b/src/core/parser/Scope.hpp
index 1ceac2e..b9b7f80 100644
--- a/src/core/parser/Scope.hpp
+++ b/src/core/parser/Scope.hpp
@@ -467,18 +467,12 @@ public:
 	}
 
 	/**
-	 * Tries to resolve all currently deferred resolution steps.
+	 * Tries to resolve all currently deferred resolution steps. The list of
+	 * pending deferred resolutions is cleared after this function has run.
 	 *
 	 * @param logger is the logger instance into which errors should be logged.
 	 */
 	bool performDeferredResolution(Logger &logger);
-
-	/**
-	 * Clears the list of currently deferred resolutions. This function may be
-	 * used to gracefully continue parsing, even after the resolution has
-	 * failed.
-	 */
-	void purgeDeferredResolutions();
 };
 }
 }
diff --git a/src/core/resource/Resource.cpp b/src/core/resource/Resource.cpp
new file mode 100644
index 0000000..349c82a
--- /dev/null
+++ b/src/core/resource/Resource.cpp
@@ -0,0 +1,46 @@
+/*
+    Ousía
+    Copyright (C) 2014, 2015  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 "Resource.hpp"
+#include "ResourceLocator.hpp"
+
+namespace ousia {
+
+/* Class Resource */
+
+Resource::Resource()
+    : Resource(false, NullResourceLocator, ResourceType::UNKNOWN, "")
+{
+}
+
+Resource::Resource(bool valid, const ResourceLocator &locator,
+                   ResourceType type, const std::string &location)
+    : valid(valid), locator(&locator), type(type), location(location)
+{
+}
+
+std::unique_ptr<std::istream> Resource::stream() const
+{
+	return locator->stream(location);
+}
+
+/* NullResource instance */
+
+const Resource NullResource{};
+}
+
diff --git a/src/core/resource/Resource.hpp b/src/core/resource/Resource.hpp
new file mode 100644
index 0000000..1934029
--- /dev/null
+++ b/src/core/resource/Resource.hpp
@@ -0,0 +1,181 @@
+/*
+    Ousía
+    Copyright (C) 2014, 2015  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 Resource.hpp
+ *
+ * Contains the Resource class, representing an external resource as well as
+ * further types used for describing resources.
+ *
+ * @author Benjamin Paaßen (bpassen@techfak.uni-bielefeld.de)
+ */
+
+#ifndef _OUSIA_RESOURCE_HPP_
+#define _OUSIA_RESOURCE_HPP_
+
+#include <map>
+#include <memory>
+#include <string>
+
+namespace ousia {
+
+// Forward declaration
+class ResourceLocator;
+
+/**
+ * This enum contains all possible types of includable resources in Ousía.
+ */
+enum class ResourceType {
+	/**
+     * Unknown type.
+     */
+	UNKNOWN,
+
+	/**
+     * The resource contains a domain description.
+     */
+	DOMAIN_DESC,
+
+	/**
+     * The resource contains a typesystem description.
+     */
+	TYPESYSTEM,
+
+	/**
+     * The resource contains a simple document.
+     */
+	DOCUMENT,
+
+	/**
+     * The resource contains style attributes.
+     */
+	ATTRIBUTES,
+
+	/**
+     * The resource is a stylesheet.
+     */
+	STYLESHEET,
+
+	/**
+     * The resource contains script (note that the actual scripting language is
+     * not specified by the resource type).
+     */
+	SCRIPT,
+
+	/**
+     * Generic data, such as e.g. images.
+     */
+	DATA
+};
+
+/**
+ * A Location contains the location of a Resource, e.g. a file path
+ * on a hard drive. Note that the 'found' flag might be set to false
+ * indicating that a resource was not found.
+ */
+class Resource {
+private:
+	/**
+	 * Specifies whether the resource points at a valid location or not.
+	 */
+	bool valid;
+
+	/**
+	 * Reference pointing at the location
+	 */
+	ResourceLocator const *locator;
+
+	/**
+	 * Requested type of the resource.
+	 */
+	ResourceType type;
+
+	/**
+	 * This is a fully qualified/canonical path to the resource found or
+	 * in an undefined state (possibly empty) if the 'valid' flag is set
+	 * to 'false'.
+	 */
+	std::string location;
+
+public:
+	/**
+	 * Default constructor of the Resource class, represents an invalid
+	 * resource.
+	 */
+	Resource();
+
+	/**
+	 * Constructor of the Resource class.
+	 *
+	 * @param valid specifies whether the Resource is valid or not.
+	 * @param locator specifies the resource locator that was used to locate the
+	 * resource.
+	 */
+	Resource(bool valid, const ResourceLocator &locator,
+	         ResourceType type, const std::string &location);
+
+	/**
+	 * This calls the 'stream' method of the underlying ResourceLocator that
+	 * found this location and returns a stream containing the data of the
+	 * Resource at this location.
+	 *
+	 * @return a stream containing the data of the Resource at this
+	 *         location. This has to be a unique_pointer because the current
+	 *         C++11 compiler does not yet support move semantics for
+	 *         streams.
+	 */
+	std::unique_ptr<std::istream> stream() const;
+
+	/**
+	 * Returns whether this resource is valid or not.
+	 *
+	 * @return true if the resource is valid, false otherwise.
+	 */
+	bool isValid() const { return valid; }
+
+	/**
+	 * Returns a reference pointing at the locator that was used to locate this
+	 * resource.
+	 *
+	 * @return the locator used for locating this resource.
+	 */
+	const ResourceLocator &getLocator() const { return *locator; }
+
+	/**
+	 * Returns the type of the resource that was requested when the resource was
+	 * located.
+	 *
+	 * @return the type of the resource.
+	 */
+	ResourceType getType() const { return type; }
+
+	/**
+	 * Returns a canonical location that can be used in a hash map to identify
+	 * a resource.
+	 */
+	const std::string &getLocation() const { return location; }
+};
+
+/**
+ * Invalid resource instance.
+ */
+extern const Resource NullResource;
+}
+
+#endif /* _OUSIA_RESOURCE_HPP_ */
+
diff --git a/src/core/resource/ResourceLocator.cpp b/src/core/resource/ResourceLocator.cpp
new file mode 100644
index 0000000..1b8490d
--- /dev/null
+++ b/src/core/resource/ResourceLocator.cpp
@@ -0,0 +1,103 @@
+/*
+    Ousía
+    Copyright (C) 2014, 2015  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 <sstream>
+
+#include "Resource.hpp"
+#include "ResourceLocator.hpp"
+
+namespace ousia {
+
+/* Class ResourceLocator */
+
+bool ResourceLocator::locate(Resource &resource, const std::string &path,
+                             const ResourceType type,
+                             const Resource &relativeTo) const
+{
+	if (&relativeTo.getLocator() == this) {
+		return doLocate(resource, path, type, relativeTo.getLocation());
+	}
+	return doLocate(resource, path, type, "");
+}
+
+bool ResourceLocator::locate(Resource &resource, const std::string &path,
+                             const ResourceType type,
+                             const std::string &relativeTo) const
+{
+	return doLocate(resource, path, type, relativeTo);
+}
+
+std::unique_ptr<std::istream> ResourceLocator::stream(
+    const std::string &location) const
+{
+	return doStream(location);
+}
+
+/* Class StaticResourceLocator */
+
+bool StaticResourceLocator::doLocate(
+    Resource &resource, const std::string &path, const ResourceType type,
+    const std::string &relativeTo) const
+{
+	auto it = resources.find(path);
+	if (it != resources.end()) {
+		resource = Resource(true, *this, type, path);
+		return true;
+	}
+	return false;
+}
+
+std::unique_ptr<std::istream> StaticResourceLocator::doStream(
+    const std::string &location) const
+{
+	auto it = resources.find(location);
+	if (it != resources.end()) {
+		return std::unique_ptr<std::istream>{new std::stringstream{it->second}};
+	}
+	return std::unique_ptr<std::istream>{new std::stringstream{""}};
+}
+
+void StaticResourceLocator::store(const std::string &path,
+                                  const std::string &data)
+{
+	auto it = resources.find(path);
+	if (it != resources.end()) {
+		it->second = data;
+	} else {
+		resources.emplace(path, data);
+	}
+}
+
+/* Class NullResourceLocatorImpl */
+
+bool NullResourceLocatorImpl::doLocate(Resource &resource,
+                                       const std::string &path,
+                                       const ResourceType type,
+                                       const std::string &relativeTo) const
+{
+	return false;
+}
+std::unique_ptr<std::istream> NullResourceLocatorImpl::doStream(
+    const std::string &location) const
+{
+	return std::unique_ptr<std::istream>{new std::stringstream{""}};
+}
+
+const NullResourceLocatorImpl NullResourceLocator;
+}
+
diff --git a/src/core/resource/ResourceLocator.hpp b/src/core/resource/ResourceLocator.hpp
new file mode 100644
index 0000000..c1d0807
--- /dev/null
+++ b/src/core/resource/ResourceLocator.hpp
@@ -0,0 +1,193 @@
+/*
+    Ousía
+    Copyright (C) 2014, 2015  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/>.
+*/
+
+#ifndef _OUSIA_RESOURCE_LOCATOR_HPP_
+#define _OUSIA_RESOURCE_LOCATOR_HPP_
+
+#include <istream>
+#include <memory>
+
+#include "Resource.hpp"
+
+namespace ousia {
+
+// Forward declaration
+class ResourceLocator;
+
+/**
+ * A ResourceLocator is a class able to locate resources in some way, usually
+ * on the hard drive.
+ *
+ * We specify this as an abstract superclass to have an interface layer between
+ * the program core and possible future extensions in terms of resource
+ * locations (e.g. online resources, .zip files, etc.).
+ */
+class ResourceLocator {
+protected:
+	/**
+	 * The locate function uses this ResourceLocator to search for a given
+	 * Resource name (path parameter). It returns a Location with the
+	 * 'valid' flag set accordingly.
+	 *
+	 * @param resource reference to a Resource the will be set the the found
+	 * location. The content of the variable will be only valid if the return
+	 * value of this function is set to true.
+	 * @param path is the resource name.
+	 * @param relativeTo is an already resolved fully qualified name/canonical
+	 * path that is to be used as base directory for this search. It is
+	 * guaranteed that the path was produced by this locator instance. Otherwise
+	 * this argument is set to an empty string.
+	 * @param type is the type of this resource.
+	 * @return true if a resource could be found, false otherwise.
+	 */
+	virtual bool doLocate(Resource &resource, const std::string &path,
+	                      const ResourceType type,
+	                      const std::string &relativeTo) const = 0;
+
+	/**
+	 * This method returns a stream containing the data of the resource at the
+	 * given location.
+	 *
+	 * @param location is a found location, most likely from a Location.
+	 *
+	 * @return a stream containing the data of the Resource at this
+	 *         location. This has to be a unique_pointer because the current
+	 *         C++11 compiler does not yet support move semantics for
+	 *         streams.
+	 */
+	virtual std::unique_ptr<std::istream> doStream(
+	    const std::string &location) const = 0;
+
+public:
+	/**
+	 * Virtual destructor of the ResourceLocator interface.
+	 */
+	virtual ~ResourceLocator() {}
+
+	/**
+	 * The locate function uses this ResourceLocator to search for a given
+	 * Resource name (path parameter).
+	 *
+	 * @param resource reference to a Resource the will be set the the found
+	 * location. The content of the variable will be only valid if the return
+	 * value of this function is set to true.
+	 * @param path is the resource name.
+	 * @param relativeTo is an already resolved Resource.
+	 * @param type is the type of this resource.
+	 * @return true if a resource could be found, false otherwise.
+	 */
+	bool locate(Resource &resource, const std::string &path,
+	            const ResourceType type = ResourceType::UNKNOWN,
+	            const Resource &relativeTo = NullResource) const;
+
+	/**
+	 * The locate function uses this ResourceLocator to search for a given
+	 * Resource name (path parameter).
+	 *
+	 * @param resource reference to a Resource the will be set the the found
+	 * location. The content of the variable will be only valid if the return
+	 * value of this function is set to true.
+	 * @param path is the resource name.
+	 * @param type is the type of this resource.
+	 * @param relativeTo is the location of an already resolved resource
+	 * relative to which this resource should be located.
+	 * @return true if a resource could be found, false otherwise.
+	 */
+	bool locate(Resource &resource, const std::string &path,
+	            const ResourceType type,
+	            const std::string &relativeTo) const;
+
+	/**
+	 * This method returns a stream containing the data of the resource at the
+	 * given location.
+	 *
+	 * @param location is a found location, most likely from a Location.
+	 *
+	 * @return a stream containing the data of the Resource at this
+	 *         location. This has to be a unique_pointer because the current
+	 *         C++11 compiler does not yet support move semantics for
+	 *         streams.
+	 */
+	std::unique_ptr<std::istream> stream(const std::string &location) const;	
+};
+
+/**
+ * The StaticResourceLocator class stores a set of predefined resources in
+ * memory and allows to return these.
+ */
+class StaticResourceLocator : public ResourceLocator {
+private:
+	/**
+	 * Map containing the paths and the corresponding stored data.
+	 */
+	std::map<std::string, std::string> resources;
+
+protected:
+	/**
+	 * Always returns false.
+	 */
+	bool doLocate(Resource &resource, const std::string &path,
+	              const ResourceType type,
+	              const std::string &relativeTo) const override;
+
+	/**
+	 * Returns an input stream containing an empty string.
+	 */
+	std::unique_ptr<std::istream> doStream(
+	    const std::string &location) const override;
+
+public:
+	/**
+	 * Stores static (string) data for the given path.
+	 *
+	 * @param path is the path the resource should be stored with.
+	 * @param data is the data that should be stored for that path.
+	 */
+	void store(const std::string &path, const std::string &data);
+};
+
+/**
+ * Implementation of the NullResourceLocator - contains a default implementation
+ * of the ResourceLocator class that does nothing. This class is e.g. used in
+ * the default constructor of the resource class. A instance of the class is
+ * provided as "NullResourceLocator".
+ */
+class NullResourceLocatorImpl : public ResourceLocator {
+protected:
+	/**
+	 * Always returns false.
+	 */
+	bool doLocate(Resource &resource, const std::string &path,
+	              const ResourceType type,
+	              const std::string &relativeTo) const override;
+
+	/**
+	 * Returns an input stream containing an empty string.
+	 */
+	std::unique_ptr<std::istream> doStream(
+	    const std::string &location) const override;
+};
+
+/**
+ * The NullResourceLocator is used as a fallback for invalid Resources.
+ */
+extern const NullResourceLocatorImpl NullResourceLocator;
+}
+
+#endif /* _RESOURCE_LOCATOR_HPP_ */
+
diff --git a/src/plugins/boost/FileLocator.cpp b/src/plugins/boost/FileLocator.cpp
index 3db214f..9ab398e 100644
--- a/src/plugins/boost/FileLocator.cpp
+++ b/src/plugins/boost/FileLocator.cpp
@@ -18,46 +18,55 @@
 
 #include "FileLocator.hpp"
 
+#include <boost/filesystem.hpp>
+
 #include <fstream>
 
 namespace ousia {
 
-void FileLocator::addSearchPath(const boost::filesystem::path &path,
-                                std::set<ResourceLocator::Type> types)
+void FileLocator::addSearchPath(const std::string &path,
+                                std::set<ResourceType> types)
 {
+	// Canonicalize the given path
+	std::string canonicalPath =
+	    boost::filesystem::canonical(path).generic_string();
+
+	// Insert the path for all given types.
 	for (auto &type : types) {
-		// retrieve the path vector for the given type.
 		auto it = searchPaths.find(type);
 		if (it != searchPaths.end()) {
-			it->second.push_back(path);
+			it->second.push_back(canonicalPath);
 		} else {
-			std::vector<boost::filesystem::path> v{path};
-			searchPaths.insert({type, v});
+			searchPaths.insert({type, {canonicalPath}});
 		}
 	}
 }
 
-ResourceLocator::Location FileLocator::locate(const std::string &path,
-                                              const std::string &relativeTo,
-                                              const Type type) const
+bool FileLocator::doLocate(Resource &resource, const std::string &path,
+                           const ResourceType type,
+                           const std::string &relativeTo) const
 {
 	boost::filesystem::path base(relativeTo);
 	if (boost::filesystem::exists(base)) {
-		// look if 'relativeTo' is a directory already.
+		// Look if 'relativeTo' is a directory already.
 		if (!boost::filesystem::is_directory(base)) {
-			// if not we use the parent directory.
+			// If not we use the parent directory.
 			base = base.parent_path();
 		}
-		// use the / operator to append the path.
+
+		// Use the / operator to append the path.
 		base /= path;
-		// if we already found a fitting resource there, use that.
+
+		// If we already found a fitting resource there, use that.
 		if (boost::filesystem::exists(base)) {
 			std::string location =
 			    boost::filesystem::canonical(base).generic_string();
-			return ResourceLocator::Location(true, *this, type, location);
+			resource = Resource(true, *this, type, location);
+			return true;
 		}
 	}
-	// otherwise look in the search paths.
+
+	// Otherwise look in the search paths.
 	auto it = searchPaths.find(type);
 	if (it != searchPaths.end()) {
 		for (boost::filesystem::path p : it->second) {
@@ -65,17 +74,15 @@ ResourceLocator::Location FileLocator::locate(const std::string &path,
 			if (boost::filesystem::exists(p)) {
 				std::string location =
 				    boost::filesystem::canonical(p).generic_string();
-				return ResourceLocator::Location(true, *this, type, location);
+				resource = Resource(true, *this, type, location);
+				return true;
 			}
 		}
 	}
-	// if we find the resource in none of the search paths we return a location.
-	// with the found flag set to false.
-	ResourceLocator::Location l(false, *this, type, "");
-	return l;
+	return false;
 }
 
-std::unique_ptr<std::istream> FileLocator::stream(
+std::unique_ptr<std::istream> FileLocator::doStream(
     const std::string &location) const
 {
 	std::unique_ptr<std::istream> ifs{new std::ifstream(location)};
diff --git a/src/plugins/boost/FileLocator.hpp b/src/plugins/boost/FileLocator.hpp
index 9cb705c..ffe5c8f 100644
--- a/src/plugins/boost/FileLocator.hpp
+++ b/src/plugins/boost/FileLocator.hpp
@@ -19,15 +19,13 @@
 #ifndef _OUSIA_FILE_LOCATOR_HPP_
 #define _OUSIA_FILE_LOCATOR_HPP_
 
-#include <core/ResourceLocator.hpp>
+#include <core/resource/Resource.hpp>
+#include <core/resource/ResourceLocator.hpp>
 
 #include <map>
 #include <set>
 #include <vector>
 
-#include <boost/filesystem.hpp>
-
-
 namespace ousia {
 
 /**
@@ -39,8 +37,25 @@ namespace ousia {
  * locations (e.g. online resources, .zip files, etc.).
  */
 class FileLocator : public ResourceLocator {
+public:
+	/**
+	 * Type alias representing a Res
+	 */
+	using SearchPaths = std::map<ResourceType, std::vector<std::string>>;
+
 private:
-	std::map<ResourceLocator::Type, std::vector<boost::filesystem::path>> searchPaths;
+	/**
+	 * Internal variable containing all stored search paths.
+	 */
+	SearchPaths searchPaths;
+
+protected:
+	bool doLocate(Resource &resource, const std::string &path,
+	              const ResourceType type,
+	              const std::string &relativeTo) const override;
+
+	std::unique_ptr<std::istream> doStream(
+	    const std::string &location) const override;
 
 public:
 	FileLocator() : searchPaths() {}
@@ -53,24 +68,23 @@ public:
 	 *              resources of the specified types at the given path in the
 	 *              future.
 	 */
-	void addSearchPath(const boost::filesystem::path &path,
-	                   std::set<ResourceLocator::Type> types);
+	void addSearchPath(const std::string &path, std::set<ResourceType> types);
+
+	/**
+	 * Adds a search path. Implicitly adds the search path for the "unknown"
+	 *
+	 * @param path is a fully qualified/canonical path to a directory.
+	 * @param types is a set of Resource Types. The FileLocator will look for
+	 *              resources of the specified types at the given path in the
+	 *              future.
+	 */
+	void addSearchPath(const std::string &path);
 
 	/**
 	 * Returns the backing map containing all search paths for a given type.
 	 * This is read-only.
 	 */
-	const std::map<ResourceLocator::Type, std::vector<boost::filesystem::path>> &
-	getSearchPaths() const
-	{
-		return searchPaths;
-	}
-
-	Location locate(const std::string &path, const std::string &relativeTo,
-	                const Type type) const override;
-
-	std::unique_ptr<std::istream> stream(
-	    const std::string &location) const override;
+	const SearchPaths &getSearchPaths() const { return searchPaths; }
 };
 }
 
diff --git a/src/plugins/xml/XmlParser.cpp b/src/plugins/xml/XmlParser.cpp
index bcac7d3..434a72c 100644
--- a/src/plugins/xml/XmlParser.cpp
+++ b/src/plugins/xml/XmlParser.cpp
@@ -60,7 +60,7 @@ public:
 
 	void start(Variant::mapType &args) override
 	{
-		scope().push(new model::Typesystem(manager(), args["name"].asString()));
+		scope().push(project()->createTypesystem(args["name"].asString()));
 	}
 
 	void end() override