diff --git a/comdel/domain/comdelvalidator.h b/comdel/domain/comdelvalidator.h
index 9c0dec7..e801062 100644
--- a/comdel/domain/comdelvalidator.h
+++ b/comdel/domain/comdelvalidator.h
@@ -8,14 +8,14 @@ namespace domain {
 
 struct ValidationError
 {
-    Instance *instance;
+    ComponentInstance *instance;
     InstanceAttribute *attribute;
     Action::ActionType type;
     std::string message;
 };
 
 struct ValidationContext {
-    Instance *instance;
+    ComponentInstance *instance;
     InstanceAttribute *attribute;
     std::map<std::string, AddressSpace> addressSpaces;
     std::map<std::string, Value> attributes;
diff --git a/comdel/domain/instance.cpp b/comdel/domain/instance.cpp
index ebc97ff..fde02d5 100644
--- a/comdel/domain/instance.cpp
+++ b/comdel/domain/instance.cpp
@@ -2,15 +2,11 @@
 
 namespace domain {
 
-
-Instance::Instance(std::string name, std::vector<InstanceAttribute> attributes, std::pair<int, int> position)
-    : name(name), attributes(attributes), position(position)
-{}
 BusInstance::BusInstance(std::string name, std::pair<int, int> position, Bus bus, int size)
-    : Instance(name, vector<InstanceAttribute>(), position), bus(bus), size(size)
+    : name(name), position(position), bus(bus), size(size)
 {}
 ComponentInstance::ComponentInstance(std::string name, std::vector<InstanceAttribute> attributes, std::pair<int, int> position, Component component)
-    : Instance(name, attributes, position), component(component)
+    : name(name), attributes(std::move(attributes)), position(position), component(component)
 {}
 
 
diff --git a/comdel/domain/instance.h b/comdel/domain/instance.h
index 8f45e29..1e8412a 100644
--- a/comdel/domain/instance.h
+++ b/comdel/domain/instance.h
@@ -12,41 +12,32 @@
 
 namespace domain {
 
-class Instance
+class BusInstance
+{
+public:
+    std::string name;
+    std::pair<int, int> position;
+
+    Bus bus;
+    int size;
+
+    BusInstance(std::string name, std::pair<int, int> position, Bus bus, int size);
+
+    virtual ~BusInstance() = default;
+};
+
+class ComponentInstance
 {
 public:
     std::string name;
     std::vector<InstanceAttribute> attributes;
     std::pair<int, int> position;
 
-    virtual ~Instance() {};
-
-    Instance(std::string name, std::vector<InstanceAttribute> attributes, std::pair<int, int> position);
-};
-
-class BusInstance: public Instance
-{
-public:
-    Bus bus;
-    int size;
-
-    BusInstance(std::string name, std::pair<int, int> position, Bus bus, int size);
-
-    virtual ~BusInstance() {
-           Instance::~Instance();
-    }
-};
-
-class ComponentInstance: public Instance
-{
-public:
     Component component;
 
     ComponentInstance(std::string name, std::vector<InstanceAttribute> attributes, std::pair<int, int> position, Component component);
 
-    virtual ~ComponentInstance() {
-        Instance::~Instance();
-    }
+    virtual ~ComponentInstance() = default;
 };
 
 } // namespace domain
diff --git a/comdel/domain/instanceattribute.h b/comdel/domain/instanceattribute.h
index b32b686..d66bdc4 100644
--- a/comdel/domain/instanceattribute.h
+++ b/comdel/domain/instanceattribute.h
@@ -15,10 +15,11 @@ class InstanceAttribute
 public:
     InstanceAttribute(std::string name, Value value, Attribute attribute);
 
-    std::string name;
+    std::string name = "";
     Value value;
     Attribute attribute;
 
+    ~InstanceAttribute() = default;
 };
 
 } // namespace domain
diff --git a/comdel/domain/schema.h b/comdel/domain/schema.h
index 70ff7d5..f8d4e61 100644
--- a/comdel/domain/schema.h
+++ b/comdel/domain/schema.h
@@ -14,18 +14,20 @@ class Schema
 public:
     Schema();
 
-
     std::vector<shared_ptr<BusInstance>> busInstances;
     std::vector<shared_ptr<ComponentInstance>> componentInstances;
 
     std::vector<shared_ptr<ConnectionInstance>> connections;
 
-    Instance *getInstance(std::string& name) {
+    BusInstance *getBusInstance(std::string& name) {
         for(auto& instance: busInstances) {
             if (instance->name == name) {
                 return instance.get();
             }
         }
+        return nullptr;
+    }
+    ComponentInstance *getComponentInstance(std::string& name) {
         for(auto& instance: componentInstances) {
             if (instance->name == name) {
                 return instance.get();
diff --git a/comdel/domain/schemacreator.cpp b/comdel/domain/schemacreator.cpp
index 271501d..ce9c0c8 100644
--- a/comdel/domain/schemacreator.cpp
+++ b/comdel/domain/schemacreator.cpp
@@ -787,7 +787,7 @@ Schema* SchemaCreator::loadSchema(SchemaNode node, Library &library)
     }
 
     for(auto &conn: node.connections) {
-        auto firstComponent = dynamic_cast<ComponentInstance*>(schema->getInstance(conn.first.instance.value));
+        auto firstComponent = schema->getComponentInstance(conn.first.instance.value);
         if(firstComponent == nullptr) {
             errors.emplace_back(conn.first.instance.span, "unknown component");
             continue;
@@ -800,7 +800,7 @@ Schema* SchemaCreator::loadSchema(SchemaNode node, Library &library)
 
         ComponentInstance *secondComponent = nullptr;
         if(conn.second.has_value()) {
-            secondComponent = dynamic_cast<ComponentInstance*>(schema->getInstance(conn.second->instance.value));
+            secondComponent = schema->getComponentInstance(conn.second->instance.value);
             if(secondComponent == nullptr) {
                 errors.emplace_back(conn.second->instance.span, "unknown component");
                 continue;
@@ -811,7 +811,7 @@ Schema* SchemaCreator::loadSchema(SchemaNode node, Library &library)
             }
         }
 
-        auto bus = dynamic_cast<BusInstance*>(schema->getInstance(conn.bus.value));
+        auto bus = schema->getBusInstance(conn.bus.value);
         if(bus == nullptr) {
             errors.emplace_back(conn.bus.span, "unknown bus");
             continue;
diff --git a/mainwindow.cpp b/mainwindow.cpp
index ae94e16..47e8186 100644
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -129,7 +129,11 @@ void MainWindow::onLoadSchema() {
 
                 for (auto& error : generator.getErrors()) {
                     parseContext.formatError(error, buffer, "ERROR: ");
+                    delete schema;
+                    schema = nullptr;
                 }
+            } else {
+                library = std::nullopt;
             }
 
             if(generator.getErrors().empty()) {
@@ -196,7 +200,6 @@ void MainWindow::onValidateSchema(bool /*toggled*/) {
         return;
     }
 
-
     this->validationErrors.clear();
 
     std::map<std::string, domain::FunctionCallback> callbacks;
@@ -246,7 +249,10 @@ void MainWindow::onValidateSchema(bool /*toggled*/) {
 
 void MainWindow::clear() {
     validationErrors.clear();
-    schema = nullptr;
+    if(schema != nullptr) {
+        delete schema;
+        schema = nullptr;
+    }
     library = std::nullopt;
 
     libraryDisplay->setLibrary(library);