Format obj and dae output predictably based on rfc notation of GlobalId. As discussed in https://sourceforge.net/p/ifcopenshell/discussion/1782717/thread/cbb0c8ca/

cmake/CMakeLists.txt

@@ -129,7 +129,7 @@ ADD_LIBRARY(IfcParse STATIC
   ../src/ifcparse/Ifc4-latebound.cpp
   ../src/ifcparse/Ifc4.cpp
   ../src/ifcparse/IfcCharacterDecoder.cpp
-  ../src/ifcparse/IfcGuidHelper.cpp
+  ../src/ifcparse/IfcGlobalId.cpp
   ../src/ifcparse/IfcHierarchyHelper.cpp
   ../src/ifcparse/IfcLateBoundEntity.cpp
   ../src/ifcparse/IfcParse.cpp
@@ -220,6 +220,7 @@ SET(include_files_parse
     ../src/ifcparse/IfcEntityDescriptor.h
     ../src/ifcparse/IfcException.h
     ../src/ifcparse/IfcFile.h
+    ../src/ifcparse/IfcGlobalId.h
     ../src/ifcparse/IfcHierarchyHelper.h
     ../src/ifcparse/IfcLateBoundEntity.h
     ../src/ifcparse/IfcParse.h

src/examples/IfcOpenHouse.cpp

@@ -43,7 +43,7 @@
 
 // Some convenience typedefs and definitions. 
 typedef std::string S;
-typedef IfcWrite::IfcGuidHelper guid;
+typedef IfcParse::IfcGlobalId guid;
 typedef std::pair<double, double> XY;
 boost::none_t const null = (static_cast<boost::none_t>(0));
 

src/ifcconvert/ColladaSerializer.cpp

@@ -28,7 +28,7 @@ std::string collada_id(const std::string& s) {
 	id.reserve(s.size());
 	for (std::string::const_iterator it = s.begin(); it != s.end(); ++it) {
 		const std::string::value_type c = *it;
-		if ((c >= '0' && c <= '9') || (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c == '_')) {
+		if ((c >= '0' && c <= '9') || (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c == '_') || ( c == '-')) {
 			id.push_back(c);
 		}
 	}
@@ -247,7 +247,7 @@ void ColladaSerializer::ColladaExporter::startDocument(const std::string& unit_n
 	asset.add();
 }
 
-void ColladaSerializer::ColladaExporter::write(const std::string& guid, const std::string& name, const std::string& type, const std::string& context, int obj_id, const std::vector<double>& matrix, const std::vector<double>& vertices, const std::vector<double>& normals, const std::vector<int>& faces, const std::vector<int>& edges, const std::vector<int>& material_ids, const std::vector<IfcGeom::Material>& _materials) {
+void ColladaSerializer::ColladaExporter::write(const std::string& unique_id, const std::string& type, const std::vector<double>& matrix, const std::vector<double>& vertices, const std::vector<double>& normals, const std::vector<int>& faces, const std::vector<int>& edges, const std::vector<int>& material_ids, const std::vector<IfcGeom::Material>& _materials) {
 	std::vector<std::string> material_references;
 	for (std::vector<IfcGeom::Material>::const_iterator it = _materials.begin(); it != _materials.end(); ++it) {
 		const IfcGeom::Material& material = *it;
@@ -256,18 +256,7 @@ void ColladaSerializer::ColladaExporter::write(const std::string& guid, const st
 		}
 		material_references.push_back(collada_id(material.name()));
 	}
-	deferreds.push_back(DeferredObject(guid, name, type, context, obj_id, matrix, vertices, normals, faces, edges, material_ids, _materials, material_references));
+	deferreds.push_back(DeferredObject(unique_id, type, matrix, vertices, normals, faces, edges, material_ids, _materials, material_references));
-}
-
-const std::string ColladaSerializer::ColladaExporter::DeferredObject::Name() const {
-	std::stringstream ss;
-	if (!this->name.empty()) {
-		ss << this->obj_id << "_" << this->name;
-	} else {
-		ss << this->guid;
-	}
-	ss << "_" << this->context;
-	return collada_id(ss.str());
 }
 
 void ColladaSerializer::ColladaExporter::endDocument() {
@@ -275,13 +264,13 @@ void ColladaSerializer::ColladaExporter::endDocument() {
 	// only at this point all objects are written to the stream.
 	materials.write();
 	for (std::vector<DeferredObject>::const_iterator it = deferreds.begin(); it != deferreds.end(); ++it) {
-		const std::string object_name = it->Name();
+		const std::string object_name = it->unique_id + "-representation";
 		geometries.write(object_name, it->type, it->vertices, it->normals, it->faces, it->edges, it->material_ids, it->materials);
 	}
 	geometries.close();
 	for (std::vector<DeferredObject>::const_iterator it = deferreds.begin(); it != deferreds.end(); ++it) {
-		const std::string object_name = it->Name();
+		const std::string object_name = it->unique_id;
-		scene.add(object_name + "-instance", object_name, object_name, it->material_references, it->matrix);
+		scene.add(object_name, object_name, object_name + "-representation", it->material_references, it->matrix);
 	}
 	scene.write();
 	stream.endDocument();
@@ -297,7 +286,7 @@ void ColladaSerializer::writeHeader() {
 
 void ColladaSerializer::write(const IfcGeom::TriangulationElement<double>* o) {
 	const IfcGeom::Representation::Triangulation<double>& mesh = o->geometry();
-	exporter.write(o->guid(), o->name(), o->type(), o->context(), o->id(), o->transformation().matrix().data(), mesh.verts(), mesh.normals(), mesh.faces(), mesh.edges(), mesh.material_ids(), mesh.materials());
+	exporter.write(o->unique_id(), o->type(), o->transformation().matrix().data(), mesh.verts(), mesh.normals(), mesh.faces(), mesh.edges(), mesh.material_ids(), mesh.materials());
 }
 
 void ColladaSerializer::finalize() {

src/ifcconvert/ColladaSerializer.h

@@ -94,8 +94,7 @@ private:
 		};
 		class DeferredObject {
 		public:
-			std::string guid, name, type, context;
+			std::string unique_id, type;
-			int obj_id;
 			std::vector<double> matrix;
 			std::vector<double> vertices;
 			std::vector<double> normals;
@@ -104,14 +103,11 @@ private:
 			std::vector<int> material_ids;
 			std::vector<IfcGeom::Material> materials;
 			std::vector<std::string> material_references;
-			DeferredObject(const std::string& guid, const std::string& name, const std::string& type, const std::string& context, int obj_id, const std::vector<double>& matrix, const std::vector<double>& vertices,
+			DeferredObject(const std::string& unique_id, const std::string& type, const std::vector<double>& matrix, const std::vector<double>& vertices,
 				const std::vector<double>& normals, const std::vector<int>& faces, const std::vector<int>& edges, const std::vector<int>& material_ids, 
 				const std::vector<IfcGeom::Material>& materials, const std::vector<std::string>& material_references)
-				: guid(guid)
+				: unique_id(unique_id)
-				, name(name)
 				, type(type)
-				, context(context)
-				, obj_id(obj_id)
 				, matrix(matrix)
 				, vertices(vertices)
 				, normals(normals)
@@ -121,7 +117,6 @@ private:
 				, materials(materials)
 				, material_references(material_references)
 			{}
-			const std::string Name() const;
 		};
 		COLLADABU::NativeString filename;
 		COLLADASW::StreamWriter stream;
@@ -139,7 +134,7 @@ private:
 		std::vector<DeferredObject> deferreds;
 		virtual ~ColladaExporter() {}
 		void startDocument(const std::string& unit_name, float unit_magnitude);
-		void write(const std::string& guid, const std::string& name, const std::string& type, const std::string& context, int obj_id, const std::vector<double>& matrix, const std::vector<double>& vertices, const std::vector<double>& normals, const std::vector<int>& faces, const std::vector<int>& edges, const std::vector<int>& material_ids, const std::vector<IfcGeom::Material>& materials);
+		void write(const std::string& unique_id, const std::string& type, const std::vector<double>& matrix, const std::vector<double>& vertices, const std::vector<double>& normals, const std::vector<int>& faces, const std::vector<int>& edges, const std::vector<int>& material_ids, const std::vector<IfcGeom::Material>& materials);
 		void endDocument();
 	};
 	ColladaExporter exporter;

src/ifcconvert/WavefrontObjSerializer.cpp

@@ -67,13 +67,7 @@ void WaveFrontOBJSerializer::writeMaterial(const IfcGeom::Material& style) {
 }
 void WaveFrontOBJSerializer::write(const IfcGeom::TriangulationElement<double>* o) {
 
-	std::string tmp = o->name().empty() ? o->guid() : o->name();
+	obj_stream << "g " << o->unique_id() << "\n";
-
-	std::replace( tmp.begin(), tmp.end(), ' ', '_');
-	std::string name = tmp;
-	name += std::string("_") + o->context();
-
-	obj_stream << "g " << name << "\n";
 	obj_stream << "s 1" << "\n";
 
 	const IfcGeom::Representation::Triangulation<double>& mesh = o->geometry();

src/ifcgeom/IfcGeomElement.h

@@ -20,10 +20,14 @@
 #ifndef IFCGEOMELEMENT_H
 #define IFCGEOMELEMENT_H
 
+#include <string>
+#include <algorithm>
+
+#include "../ifcparse/IfcGlobalId.h"
+
 #include "../ifcgeom/IfcGeomRepresentation.h"
 #include "../ifcgeom/IfcGeomIteratorSettings.h"
 
-
 namespace IfcGeom {
 
 	template <typename P>
@@ -73,6 +77,7 @@ namespace IfcGeom {
 		std::string _type;
 		std::string _guid;
 		std::string _context;
+		std::string _unique_id;
 		Transformation<P> _transformation;
 	public:
 		int id() const { return _id; }
@@ -81,10 +86,21 @@ namespace IfcGeom {
 		const std::string& type() const { return _type; }
 		const std::string& guid() const { return _guid; }
 		const std::string& context() const { return _context; }
+		const std::string& unique_id() const { return _unique_id; }
 		const Transformation<P>& transformation() const { return _transformation; }
 		Element(const ElementSettings& settings, int id, int parent_id, const std::string& name, const std::string& type, const std::string& guid, const std::string& context, const gp_Trsf& trsf)
 			: _id(id), _parent_id(parent_id), _name(name), _type(type), _guid(guid), _context(context), _transformation(settings, trsf)
-		{}
+		{
+			std::ostringstream oss;
+			oss << "product-" << IfcParse::IfcGlobalId(guid).formatted();
+			if (!_context.empty()) {
+				std::string ctx = _context;
+				std::transform(ctx.begin(), ctx.end(), ctx.begin(), ::tolower);
+				std::replace(ctx.begin(), ctx.end(), ' ', '-');
+				oss << "-" << ctx;
+			}
+			_unique_id = oss.str();
+		}
 		virtual ~Element() {}
 	};
 

src/ifcgeom/IfcGeomRenderStyles.h

@@ -57,17 +57,20 @@ namespace IfcGeom {
 		boost::optional<double> specularity;
 	public:
 		SurfaceStyle() {
-			this->name = "IfcSurfaceStyleShading";
+			this->name = "surface-style";
 		}
 		SurfaceStyle(int id) : id(id) {
 			std::stringstream sstr; 
-			sstr << "IfcSurfaceStyleShading_" << id; 
+			sstr << "surface-style-" << id; 
 			this->name = sstr.str(); 
 		}
 		SurfaceStyle(const std::string& name) : name(name) {}
 		SurfaceStyle(int id, const std::string& name) : id(id) {
 			std::stringstream sstr; 
-			sstr << id << "_" << name;
+			std::string sanitized = name;
+			std::transform(sanitized.begin(), sanitized.end(), sanitized.begin(), ::tolower);
+			std::replace(sanitized.begin(), sanitized.end(), ' ', '-');
+			sstr << "surface-style-" << id << "-" << sanitized;
 			this->name = sstr.str(); 
 		}
 		

src/ifcopenshell-python/ifcopenshell/__init__.py

@@ -108,6 +108,8 @@ class file(object):
 			return entity_instance(self.wrapped_data.by_id(key))
 		elif isinstance(key, str):
 			return entity_instance(self.wrapped_data.by_guid(key))
+	def by_id(self, id): return self[id]
+	def by_guid(self, guid): return self[guid]
 	def add(self, inst):
 		inst.wrapped_data.this.disown()
 		return entity_instance(self.wrapped_data.add(inst.wrapped_data))

src/ifcparse/IfcGlobalId.cpp

@@ -17,91 +17,112 @@
  *                                                                              *
  ********************************************************************************/
 
-/********************************************************************************
+#include <vector>
- *                                                                              *
- * Please consider this a placeholder for an actual GlobalId generation         *
- * algorithm. A real implementation could for example be based on Boost::uuid   *
- *                                                                              *
- ********************************************************************************/
-
-#include <time.h>
-#include <stdlib.h>
 #include <algorithm>
 
 #include <boost/uuid/uuid.hpp>
 #include <boost/uuid/uuid_generators.hpp>
 #include <boost/uuid/uuid_io.hpp>
 
-#include "../ifcparse/IfcWrite.h"
+#include "../ifcparse/IfcGlobalId.h"
 #include "../ifcparse/IfcException.h"
 
 static const char* chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_$";
 
 // Converts an unsigned integer into a base64 string of length l
 std::string base64(unsigned v, int l) {
-    std::string r;
+	std::string r;
-    r.reserve(l);
+	r.reserve(l);
-    while ( v ) {
+	while ( v ) {
-        r.push_back(chars[v%64]);
+		r.push_back(chars[v%64]);
-        v /= 64;
+		v /= 64;
-    }
+	}
-    while ( r.size() != l ) r.push_back('0');
+	while ( r.size() != l ) r.push_back('0');
-    std::reverse(r.begin(),r.end());
+	std::reverse(r.begin(),r.end());
-    return r;
+	return r;
 }
 
 // Converts a base64 string into an unsigned integer
 unsigned from_base64(const std::string& s) {
-    std::string::size_type zeros = s.find_first_not_of('0');
+	std::string::size_type zeros = s.find_first_not_of('0');
-    unsigned r = 0;
+	unsigned r = 0;
-    if ( zeros != std::string::npos )
+	if ( zeros != std::string::npos )
-        for ( std::string::const_iterator i = s.begin()+zeros; i != s.end(); ++ i ) {
+		for ( std::string::const_iterator i = s.begin()+zeros; i != s.end(); ++ i ) {
-            r *= 64;
+			r *= 64;
-            const char* c = strchr(chars,*i);
+			const char* c = strchr(chars,*i);
-            if ( !c ) throw IfcParse::IfcException("Failed to decode GlobalId");
+			if ( !c ) throw IfcParse::IfcException("Failed to decode GlobalId");
-            r += (c-chars);
+			r += (c-chars);
-        }
+		}
-    return r;
+	return r;
 }
 
 // Compresses the UUID byte array into a base64 representation
 std::string compress(unsigned char* v) {
-    std::string r;
+	std::string r;
-    r.reserve(22);
+	r.reserve(22);
-    r += base64(v[0],2);
+	r += base64(v[0],2);
-    for ( unsigned i = 1; i < 16; i += 3 ) {
+	for ( unsigned i = 1; i < 16; i += 3 ) {
-        r += base64((v[i]<<16) + (v[i+1]<<8) + v[i+2],4);
+		r += base64((v[i]<<16) + (v[i+1]<<8) + v[i+2],4);
-    }
+	}
-    return r;
+	return r;
 }
 
 // Expands the base64 representation into a UUID byte array
 void expand(const std::string& s, std::vector<unsigned char>& v) {
-    v.push_back(from_base64(s.substr(0,2)));
+	v.push_back(from_base64(s.substr(0,2)));
-    for( unsigned i = 0; i < 5; ++i ) {
+	for( unsigned i = 0; i < 5; ++i ) {
-        unsigned d = from_base64(s.substr(2+4*i,4));
+		unsigned d = from_base64(s.substr(2+4*i,4));
-        for ( unsigned j = 0; j < 3; ++ j ) {
+		for ( unsigned j = 0; j < 3; ++ j ) {
-            v.push_back((d>>(8*(2-j))) % 256);
+			v.push_back((d>>(8*(2-j))) % 256);
-        }
+		}
-    }
+	}
 }
 
 // A random number generator for the UUID
 static boost::uuids::basic_random_generator<boost::mt19937> gen;
 
-IfcWrite::IfcGuidHelper::IfcGuidHelper() {
+IfcParse::IfcGlobalId::IfcGlobalId() {
-    boost::uuids::uuid u = gen();
+	uuid_data = gen();
-    std::vector<unsigned char> v(u.size());
+	std::vector<unsigned char> v(uuid_data.size());
-    std::copy(u.begin(), u.end(), v.begin());
+	std::copy(uuid_data.begin(), uuid_data.end(), v.begin());
-    data = compress(&v[0]);
+	string_data = compress(&v[0]);
+	formatted_string = boost::uuids::to_string(uuid_data);
 
-    std::vector<unsigned char> v2;
+#ifndef NDEBUG
-    expand(data,v2);
+	std::vector<unsigned char> test_vector;
-    boost::uuids::uuid u2;
+	expand(string_data, test_vector);
-    std::copy(v2.begin(), v2.end(), u2.begin());
+	boost::uuids::uuid test_uuid;
-}
+	std::copy(test_vector.begin(), test_vector.end(), test_uuid.begin());
-IfcWrite::IfcGuidHelper::operator std::string() const {
+	if (uuid_data != test_uuid) {
-	return data;
+		throw IfcParse::IfcException("Internal error generating GlobalId");
+	}
+#endif
 }
 
-bool IfcWrite::IfcGuidHelper::seeded = false;
+IfcParse::IfcGlobalId::IfcGlobalId(const std::string& s)
+	: string_data(s)
+{
+	std::vector<unsigned char> v;
+	expand(string_data, v);
+	std::copy(v.begin(), v.end(), uuid_data.begin());
+	formatted_string = boost::uuids::to_string(uuid_data);
+
+#ifndef NDEBUG
+	const std::string test_string = compress(&uuid_data.data[0]);
+	if (string_data != test_string) {
+		throw IfcParse::IfcException("Internal error generating GlobalId");
+	}
+#endif
+}
+
+IfcParse::IfcGlobalId::operator const std::string&() const {
+	return string_data;
+}
+
+IfcParse::IfcGlobalId::operator const boost::uuids::uuid&() const {
+	return uuid_data;
+}
+
+const std::string& IfcParse::IfcGlobalId::formatted() const {
+	return formatted_string;
+}

src/ifcparse/IfcGlobalId.h

@@ -0,0 +1,44 @@
+/********************************************************************************
+ *                                                                              *
+ * This file is part of IfcOpenShell.                                           *
+ *                                                                              *
+ * IfcOpenShell is free software: you can redistribute it and/or modify         *
+ * it under the terms of the Lesser GNU General Public License as published by  *
+ * the Free Software Foundation, either version 3.0 of the License, or          *
+ * (at your option) any later version.                                          *
+ *                                                                              *
+ * IfcOpenShell 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                 *
+ * Lesser GNU General Public License for more details.                          *
+ *                                                                              *
+ * You should have received a copy of the Lesser GNU General Public License     *
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.         *
+ *                                                                              *
+ ********************************************************************************/
+
+#ifndef IFCGLOBALID_H
+#define IFCGLOBALID_H
+
+#include <string>
+#include <boost/uuid/uuid.hpp>
+
+namespace IfcParse {
+
+	/// A helper class for the creation of IFC GlobalIds.
+	class IfcGlobalId {
+	private:
+		std::string string_data, formatted_string;
+		boost::uuids::uuid uuid_data;
+	public:
+		static const unsigned int length = 22;
+		IfcGlobalId();
+		IfcGlobalId(const std::string&);
+		operator const std::string&() const;
+		operator const boost::uuids::uuid&() const;
+		const std::string& formatted() const;
+	};
+
+}
+
+#endif

src/ifcparse/IfcHierarchyHelper.cpp

@@ -108,7 +108,7 @@ IfcSchema::IfcProject* IfcHierarchyHelper::addProject(IfcSchema::IfcOwnerHistory
 
 	IfcSchema::IfcUnitAssignment* unit_assignment = new IfcSchema::IfcUnitAssignment(units);
 
-	IfcSchema::IfcProject* project = new IfcSchema::IfcProject(IfcWrite::IfcGuidHelper(), owner_hist, boost::none, boost::none, 
+	IfcSchema::IfcProject* project = new IfcSchema::IfcProject(IfcParse::IfcGlobalId(), owner_hist, boost::none, boost::none, 
 		boost::none, boost::none, boost::none, rep_contexts, unit_assignment);
 
 	addEntity(dimexp);
@@ -146,7 +146,7 @@ IfcSchema::IfcSite* IfcHierarchyHelper::addSite(IfcSchema::IfcProject* proj, Ifc
 		proj = addProject(owner_hist);
 	}
 
-	IfcSchema::IfcSite* site = new IfcSchema::IfcSite(IfcWrite::IfcGuidHelper(), owner_hist, boost::none, 
+	IfcSchema::IfcSite* site = new IfcSchema::IfcSite(IfcParse::IfcGlobalId(), owner_hist, boost::none, 
 		boost::none, boost::none, addLocalPlacement(), 0, boost::none, 
 		IfcSchema::IfcElementCompositionEnum::IfcElementComposition_ELEMENT, 
 		boost::none, boost::none, boost::none, boost::none, 0);
@@ -169,7 +169,7 @@ IfcSchema::IfcBuilding* IfcHierarchyHelper::addBuilding(IfcSchema::IfcSite* site
 	if (! site) {
 		site = addSite(0, owner_hist);
 	}
-	IfcSchema::IfcBuilding* building = new IfcSchema::IfcBuilding(IfcWrite::IfcGuidHelper(), owner_hist, boost::none, boost::none, boost::none, 
+	IfcSchema::IfcBuilding* building = new IfcSchema::IfcBuilding(IfcParse::IfcGlobalId(), owner_hist, boost::none, boost::none, boost::none, 
 		addLocalPlacement(), 0, boost::none, IfcSchema::IfcElementCompositionEnum::IfcElementComposition_ELEMENT, 
 		boost::none, boost::none, 0);
 
@@ -195,7 +195,7 @@ IfcSchema::IfcBuildingStorey* IfcHierarchyHelper::addBuildingStorey(IfcSchema::I
 	if (! building) {
 		building = addBuilding(0, owner_hist);
 	}
-	IfcSchema::IfcBuildingStorey* storey = new IfcSchema::IfcBuildingStorey(IfcWrite::IfcGuidHelper(), 
+	IfcSchema::IfcBuildingStorey* storey = new IfcSchema::IfcBuildingStorey(IfcParse::IfcGlobalId(), 
 		owner_hist, boost::none, boost::none, boost::none, addLocalPlacement(), 0, boost::none, 
 		IfcSchema::IfcElementCompositionEnum::IfcElementComposition_ELEMENT, boost::none);
 

src/ifcparse/IfcHierarchyHelper.h

@@ -35,8 +35,10 @@
 #else
 #include "../ifcparse/Ifc2x3.h"
 #endif
+
 #include "../ifcparse/IfcFile.h"
 #include "../ifcparse/IfcWrite.h"
+#include "../ifcparse/IfcGlobalId.h"
 
 class IfcHierarchyHelper : public IfcParse::IfcFile {
 public:
@@ -100,7 +102,7 @@ public:
 			}
 			IfcSchema::IfcObjectDefinition::list::ptr relating_objects (new IfcTemplatedEntityList<IfcSchema::IfcObjectDefinition>());
 			relating_objects->push(relating_object);
-			T* t = new T(IfcWrite::IfcGuidHelper(), owner_hist, boost::none, boost::none, related_object, relating_objects);
+			T* t = new T(IfcParse::IfcGlobalId(), owner_hist, boost::none, boost::none, related_object, relating_objects);
 			addEntity(t);
 		}
 	}
@@ -196,7 +198,7 @@ inline void IfcHierarchyHelper::addRelatedObject <IfcSchema::IfcRelContainedInSp
 		}
 		IfcSchema::IfcProduct::list::ptr relating_objects (new IfcTemplatedEntityList<IfcSchema::IfcProduct>());
 		relating_objects->push((IfcSchema::IfcProduct*)relating_object);
-		IfcSchema::IfcRelContainedInSpatialStructure* t = new IfcSchema::IfcRelContainedInSpatialStructure(IfcWrite::IfcGuidHelper(), owner_hist, 
+		IfcSchema::IfcRelContainedInSpatialStructure* t = new IfcSchema::IfcRelContainedInSpatialStructure(IfcParse::IfcGlobalId(), owner_hist, 
 			boost::none, boost::none, relating_objects, (IfcSchema::IfcSpatialStructureElement*)related_object);
 
 		addEntity(t);

src/ifcparse/IfcWrite.h

@@ -136,17 +136,6 @@ namespace IfcWrite {
 		IfcUtil::ArgumentType type() const;
 	};
 
-	/// A helper class for the creation of IFC GlobalIds.
-	class IfcGuidHelper {
-	private:
-		std::string data;
-		static bool seeded;
-	public:
-		static const unsigned int length = 22;
-		IfcGuidHelper();
-		operator std::string() const;
-	};
-
 	// Accumulates all schema instances created from constructors
 	// This way they can be added in a single batch to the IfcFile
 	class EntityBuffer {

src/ifcwrap/IfcGeomWrapper.i

@@ -146,6 +146,7 @@
 			type = property(type)
 			guid = property(guid)
 			context = property(context)
+			unique_id = property(unique_id)
 			transformation = property(transformation)
     %}
 };

win/IfcParse.vcproj

@@ -222,7 +222,7 @@
 				>
 			</File>
 			<File
-				RelativePath="..\src\ifcparse\IfcGuidHelper.cpp"
+				RelativePath="..\src\ifcparse\IfcGlobalId.cpp"
 				>
 			</File>
 			<File
@@ -279,6 +279,10 @@
 				RelativePath="..\src\ifcparse\IfcFile.h"
 				>
 			</File>
+			<File
+				RelativePath="..\src\ifcparse\IfcGlobalId.h"
+				>
+			</File>
 			<File
 				RelativePath="..\src\ifcparse\IfcHierarchyHelper.h"
 				>