diff --git a/jps/jps-builders/src/org/jetbrains/jps/incremental/artifacts/impl/JpsBuilderArtifactServiceImpl.java b/jps/jps-builders/src/org/jetbrains/jps/incremental/artifacts/impl/JpsBuilderArtifactServiceImpl.java
index c9a5c8000abb..f2a4e232ee87 100644
--- a/jps/jps-builders/src/org/jetbrains/jps/incremental/artifacts/impl/JpsBuilderArtifactServiceImpl.java
+++ b/jps/jps-builders/src/org/jetbrains/jps/incremental/artifacts/impl/JpsBuilderArtifactServiceImpl.java
@@ -3,11 +3,11 @@ package org.jetbrains.jps.incremental.artifacts.impl;
 import com.intellij.util.containers.ContainerUtil;
 import org.jetbrains.jps.incremental.artifacts.JpsBuilderArtifactService;
 import org.jetbrains.jps.incremental.artifacts.JpsSyntheticArtifactProvider;
+import org.jetbrains.jps.model.JpsElementCollection;
 import org.jetbrains.jps.model.JpsModel;
 import org.jetbrains.jps.model.artifact.JpsArtifact;
 import org.jetbrains.jps.model.artifact.JpsArtifactService;
 import org.jetbrains.jps.model.impl.JpsElementChildRoleBase;
-import org.jetbrains.jps.model.impl.JpsElementCollectionImpl;
 import org.jetbrains.jps.model.impl.JpsElementCollectionRole;
 import org.jetbrains.jps.service.JpsServiceManager;
 
@@ -31,7 +31,7 @@ public class JpsBuilderArtifactServiceImpl extends JpsBuilderArtifactService {
   }
 
   public List<JpsArtifact> getSyntheticArtifacts(final JpsModel model) {
-    JpsElementCollectionImpl<JpsArtifact> artifactsCollection = model.getProject().getContainer().getChild(SYNTHETIC_ARTIFACTS);
+    JpsElementCollection<JpsArtifact> artifactsCollection = model.getProject().getContainer().getChild(SYNTHETIC_ARTIFACTS);
     if (artifactsCollection == null) {
       List<JpsArtifact> artifactList = computeSyntheticArtifacts(model);
       artifactsCollection = model.getProject().getContainer().setChild(SYNTHETIC_ARTIFACTS);
diff --git a/jps/model-api/src/org/jetbrains/jps/model/JpsElementCollection.java b/jps/model-api/src/org/jetbrains/jps/model/JpsElementCollection.java
index 5010f06e4ffb..4e9cb975258b 100644
--- a/jps/model-api/src/org/jetbrains/jps/model/JpsElementCollection.java
+++ b/jps/model-api/src/org/jetbrains/jps/model/JpsElementCollection.java
@@ -16,4 +16,9 @@ public interface JpsElementCollection<E extends JpsElement> extends JpsElement {
   <X extends E> X addChild(X element);
 
   void removeChild(@NotNull E element);
+
+  void removeAllChildren();
+
+  <X extends JpsTypedElement<P>, P extends JpsElement>
+  Iterable<X> getElementsOfType(@NotNull JpsElementType<P> type);
 }
diff --git a/jps/model-impl/src/org/jetbrains/jps/model/artifact/impl/JpsArtifactServiceImpl.java b/jps/model-impl/src/org/jetbrains/jps/model/artifact/impl/JpsArtifactServiceImpl.java
index 436e6b94f384..994bb9689007 100644
--- a/jps/model-impl/src/org/jetbrains/jps/model/artifact/impl/JpsArtifactServiceImpl.java
+++ b/jps/model-impl/src/org/jetbrains/jps/model/artifact/impl/JpsArtifactServiceImpl.java
@@ -2,13 +2,13 @@ package org.jetbrains.jps.model.artifact.impl;
 
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jps.model.JpsElement;
+import org.jetbrains.jps.model.JpsElementCollection;
 import org.jetbrains.jps.model.JpsProject;
 import org.jetbrains.jps.model.artifact.JpsArtifact;
 import org.jetbrains.jps.model.artifact.JpsArtifactReference;
 import org.jetbrains.jps.model.artifact.JpsArtifactService;
 import org.jetbrains.jps.model.artifact.JpsArtifactType;
 import org.jetbrains.jps.model.artifact.elements.JpsCompositePackagingElement;
-import org.jetbrains.jps.model.impl.JpsElementCollectionImpl;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -22,7 +22,7 @@ public class JpsArtifactServiceImpl extends JpsArtifactService {
 
   @Override
   public List<JpsArtifact> getArtifacts(@NotNull JpsProject project) {
-    JpsElementCollectionImpl<JpsArtifact> collection = project.getContainer().getChild(JpsArtifactRole.ARTIFACT_COLLECTION_ROLE);
+    JpsElementCollection<JpsArtifact> collection = project.getContainer().getChild(JpsArtifactRole.ARTIFACT_COLLECTION_ROLE);
     return collection != null ? collection.getElements() : Collections.<JpsArtifact>emptyList();
   }
 
diff --git a/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsElementCollectionImpl.java b/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsElementCollectionImpl.java
index 3d33d4f152e1..a190a539ced7 100644
--- a/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsElementCollectionImpl.java
+++ b/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsElementCollectionImpl.java
@@ -22,7 +22,7 @@ public class JpsElementCollectionImpl<E extends JpsElement> extends JpsElementBa
     myCopyToOriginal = null;
   }
 
-  public JpsElementCollectionImpl(JpsElementCollectionImpl<E> original) {
+  private JpsElementCollectionImpl(JpsElementCollectionImpl<E> original) {
     myChildRole = original.myChildRole;
     myElements = new SmartList<E>();
     myCopyToOriginal = new HashMap<E, E>();
@@ -40,8 +40,9 @@ public class JpsElementCollectionImpl<E extends JpsElement> extends JpsElementBa
     return myElements;
   }
 
-  public <X extends E, P extends JpsElement> Iterable<X> getElementsOfType(@NotNull final JpsElementType<P> type) {
-    return new JpsElementIterable<X>(type);
+  @Override
+  public <X extends JpsTypedElement<P>, P extends JpsElement> Iterable<X> getElementsOfType(@NotNull final JpsElementType<P> type) {
+    return new JpsElementIterable<X, P>(type);
   }
 
   @NotNull
@@ -73,6 +74,7 @@ public class JpsElementCollectionImpl<E extends JpsElement> extends JpsElementBa
     }
   }
 
+  @Override
   public void removeAllChildren() {
     List<E> elements = new ArrayList<E>(myElements);
     for (E element : elements) {
@@ -111,19 +113,21 @@ public class JpsElementCollectionImpl<E extends JpsElement> extends JpsElementBa
     }
   }
 
-  private class JpsElementIterable<X extends E> implements Iterable<X> {
+  private class JpsElementIterable<X extends JpsTypedElement<P>, P extends JpsElement> implements Iterable<X> {
     private final JpsElementType<? extends JpsElement> myType;
 
-    public JpsElementIterable(JpsElementType<? extends JpsElement> type) {
+    public JpsElementIterable(JpsElementType<P> type) {
       myType = type;
     }
 
     @Override
     public Iterator<X> iterator() {
-      return new FilteringIterator<E, X>(myElements.iterator(), new Condition<E>() {
+      //noinspection unchecked
+      Iterator<JpsTypedElement<?>> iterator = (Iterator<JpsTypedElement<?>>)myElements.iterator();
+      return new FilteringIterator<JpsTypedElement<?>, X>(iterator, new Condition<JpsTypedElement<?>>() {
         @Override
-        public boolean value(E e) {
-          return e instanceof JpsTypedElement && ((JpsTypedElement<?>)e).getType().equals(myType);
+        public boolean value(JpsTypedElement<?> e) {
+          return e.getType().equals(myType);
         }
       });
     }
diff --git a/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsElementCollectionRole.java b/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsElementCollectionRole.java
index 79e5cc39ec95..364beffa748b 100644
--- a/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsElementCollectionRole.java
+++ b/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsElementCollectionRole.java
@@ -6,8 +6,8 @@ import org.jetbrains.jps.model.*;
 /**
  * @author nik
  */
-public class JpsElementCollectionRole<E extends JpsElement> extends JpsElementChildRoleBase<JpsElementCollectionImpl<E>>
-                                                            implements JpsElementCreator<JpsElementCollectionImpl<E>> {
+public class JpsElementCollectionRole<E extends JpsElement> extends JpsElementChildRoleBase<JpsElementCollection<E>>
+                                                            implements JpsElementCreator<JpsElementCollection<E>> {
   private final JpsElementChildRole<E> myChildRole;
 
   private JpsElementCollectionRole(@NotNull JpsElementChildRole<E> role) {
@@ -17,7 +17,7 @@ public class JpsElementCollectionRole<E extends JpsElement> extends JpsElementCh
 
   @NotNull
   @Override
-  public JpsElementCollectionImpl<E> create() {
+  public JpsElementCollection<E> create() {
     return new JpsElementCollectionImpl<E>(myChildRole);
   }
 
diff --git a/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsNamedElementReferenceBase.java b/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsNamedElementReferenceBase.java
index 6b70b0c7f86b..2432b6509a88 100644
--- a/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsNamedElementReferenceBase.java
+++ b/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsNamedElementReferenceBase.java
@@ -29,7 +29,7 @@ public abstract class JpsNamedElementReferenceBase<S extends JpsNamedElement, T
     final JpsCompositeElement parent = getParentReference().resolve();
     if (parent == null) return null;
 
-    JpsElementCollectionImpl<? extends S> collection = getCollection(parent);
+    JpsElementCollection<? extends S> collection = getCollection(parent);
     if (collection == null) return null;
 
     final List<? extends S> elements = collection.getElements();
@@ -45,7 +45,7 @@ public abstract class JpsNamedElementReferenceBase<S extends JpsNamedElement, T
   }
 
   @Nullable
-  protected abstract JpsElementCollectionImpl<? extends S> getCollection(@NotNull JpsCompositeElement parent);
+  protected abstract JpsElementCollection<? extends S> getCollection(@NotNull JpsCompositeElement parent);
 
   @Nullable
   protected abstract T resolve(S element);
diff --git a/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsNamedElementReferenceImpl.java b/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsNamedElementReferenceImpl.java
index 45ebab4d6129..1e2a8d20bf93 100644
--- a/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsNamedElementReferenceImpl.java
+++ b/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsNamedElementReferenceImpl.java
@@ -3,6 +3,7 @@ package org.jetbrains.jps.model.impl;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jps.model.JpsCompositeElement;
+import org.jetbrains.jps.model.JpsElementCollection;
 import org.jetbrains.jps.model.JpsElementReference;
 import org.jetbrains.jps.model.JpsNamedElement;
 
@@ -29,7 +30,7 @@ public abstract class JpsNamedElementReferenceImpl<T extends JpsNamedElement, Se
   }
 
   @Nullable
-  protected JpsElementCollectionImpl<? extends T> getCollection(@NotNull JpsCompositeElement parent) {
+  protected JpsElementCollection<? extends T> getCollection(@NotNull JpsCompositeElement parent) {
     return parent.getContainer().getChild(myCollectionRole);
   }
 }
diff --git a/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsProjectImpl.java b/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsProjectImpl.java
index fefe103b525a..47858e6926d2 100644
--- a/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsProjectImpl.java
+++ b/jps/model-impl/src/org/jetbrains/jps/model/impl/JpsProjectImpl.java
@@ -47,7 +47,7 @@ public class JpsProjectImpl extends JpsRootElementBase<JpsProjectImpl> implement
   public
   <P extends JpsElement, ModuleType extends JpsModuleType<P> & JpsElementTypeWithDefaultProperties<P>>
   JpsModule addModule(@NotNull final String name, @NotNull ModuleType moduleType) {
-    final JpsElementCollectionImpl<JpsModule> collection = myContainer.getChild(JpsModuleRole.MODULE_COLLECTION_ROLE);
+    final JpsElementCollection<JpsModule> collection = myContainer.getChild(JpsModuleRole.MODULE_COLLECTION_ROLE);
     return collection.addChild(new JpsModuleImpl<P>(moduleType, name, moduleType.createDefaultProperties()));
   }
 
diff --git a/jps/model-impl/src/org/jetbrains/jps/model/library/impl/JpsLibraryCollectionImpl.java b/jps/model-impl/src/org/jetbrains/jps/model/library/impl/JpsLibraryCollectionImpl.java
index 473520fd7c34..433038828247 100644
--- a/jps/model-impl/src/org/jetbrains/jps/model/library/impl/JpsLibraryCollectionImpl.java
+++ b/jps/model-impl/src/org/jetbrains/jps/model/library/impl/JpsLibraryCollectionImpl.java
@@ -2,8 +2,8 @@ package org.jetbrains.jps.model.library.impl;
 
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jps.model.JpsElement;
+import org.jetbrains.jps.model.JpsElementCollection;
 import org.jetbrains.jps.model.JpsElementTypeWithDefaultProperties;
-import org.jetbrains.jps.model.impl.JpsElementCollectionImpl;
 import org.jetbrains.jps.model.library.JpsLibrary;
 import org.jetbrains.jps.model.library.JpsLibraryCollection;
 import org.jetbrains.jps.model.library.JpsLibraryType;
@@ -15,9 +15,9 @@ import java.util.List;
  * @author nik
  */
 public class JpsLibraryCollectionImpl implements JpsLibraryCollection {
-  private final JpsElementCollectionImpl<JpsLibrary> myCollection;
+  private final JpsElementCollection<JpsLibrary> myCollection;
 
-  public JpsLibraryCollectionImpl(JpsElementCollectionImpl<JpsLibrary> collection) {
+  public JpsLibraryCollectionImpl(JpsElementCollection<JpsLibrary> collection) {
     myCollection = collection;
   }
 
diff --git a/jps/model-impl/src/org/jetbrains/jps/model/library/impl/JpsSdkReferenceImpl.java b/jps/model-impl/src/org/jetbrains/jps/model/library/impl/JpsSdkReferenceImpl.java
index 02b224eca7b1..a409435a75c6 100644
--- a/jps/model-impl/src/org/jetbrains/jps/model/library/impl/JpsSdkReferenceImpl.java
+++ b/jps/model-impl/src/org/jetbrains/jps/model/library/impl/JpsSdkReferenceImpl.java
@@ -4,8 +4,8 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jps.model.JpsCompositeElement;
 import org.jetbrains.jps.model.JpsElement;
+import org.jetbrains.jps.model.JpsElementCollection;
 import org.jetbrains.jps.model.JpsElementReference;
-import org.jetbrains.jps.model.impl.JpsElementCollectionImpl;
 import org.jetbrains.jps.model.impl.JpsNamedElementReferenceBase;
 import org.jetbrains.jps.model.library.JpsLibrary;
 import org.jetbrains.jps.model.library.JpsTypedLibrary;
@@ -47,7 +47,7 @@ public class JpsSdkReferenceImpl<P extends JpsElement> extends JpsNamedElementRe
   }
 
   @Nullable
-  protected JpsElementCollectionImpl<? extends JpsLibrary> getCollection(@NotNull JpsCompositeElement parent) {
+  protected JpsElementCollection<? extends JpsLibrary> getCollection(@NotNull JpsCompositeElement parent) {
     return parent.getContainer().getChild(JpsLibraryRole.LIBRARIES_COLLECTION_ROLE);
   }
 }
diff --git a/jps/model-impl/src/org/jetbrains/jps/model/module/impl/JpsModuleImpl.java b/jps/model-impl/src/org/jetbrains/jps/model/module/impl/JpsModuleImpl.java
index 1346467b912c..8b164fff8af3 100644
--- a/jps/model-impl/src/org/jetbrains/jps/model/module/impl/JpsModuleImpl.java
+++ b/jps/model-impl/src/org/jetbrains/jps/model/module/impl/JpsModuleImpl.java
@@ -113,7 +113,7 @@ public class JpsModuleImpl<P extends JpsElement> extends JpsNamedCompositeElemen
 
   @Override
   public void removeSourceRoot(@NotNull String url, @NotNull JpsModuleSourceRootType rootType) {
-    final JpsElementCollectionImpl<JpsModuleSourceRoot> roots = myContainer.getChild(JpsModuleSourceRootRole.ROOT_COLLECTION_ROLE);
+    final JpsElementCollection<JpsModuleSourceRoot> roots = myContainer.getChild(JpsModuleSourceRootRole.ROOT_COLLECTION_ROLE);
     for (JpsModuleSourceRoot root : roots.getElements()) {
       if (root.getRootType().equals(rootType) && root.getUrl().equals(url)) {
         roots.removeChild(root);
diff --git a/jps/model-impl/testSrc/org/jetbrains/jps/model/JpsLibraryTest.java b/jps/model-impl/testSrc/org/jetbrains/jps/model/JpsLibraryTest.java
index b6dd3cdce310..d285a7116d39 100644
--- a/jps/model-impl/testSrc/org/jetbrains/jps/model/JpsLibraryTest.java
+++ b/jps/model-impl/testSrc/org/jetbrains/jps/model/JpsLibraryTest.java
@@ -1,12 +1,22 @@
 package org.jetbrains.jps.model;
 
+import com.intellij.util.containers.ContainerUtilRt;
 import org.jetbrains.jps.model.java.JpsJavaLibraryType;
+import org.jetbrains.jps.model.java.JpsJavaSdkType;
 import org.jetbrains.jps.model.library.*;
 
 /**
  * @author nik
  */
 public class JpsLibraryTest extends JpsModelTestCase {
+  public void testAddLibrary() {
+    JpsLibrary a = myProject.addLibrary("a", JpsJavaLibraryType.INSTANCE);
+    JpsLibraryCollection collection = myProject.getLibraryCollection();
+    assertSameElements(collection.getLibraries(), a);
+    assertSameElements(ContainerUtilRt.newArrayList(collection.getLibraries(JpsJavaLibraryType.INSTANCE)), a);
+    assertEmpty(ContainerUtilRt.newArrayList(collection.getLibraries(JpsJavaSdkType.INSTANCE)));
+  }
+
   public void testAddRoot() {
     final JpsLibrary library = myProject.addLibrary("a", JpsJavaLibraryType.INSTANCE);
     library.addRoot("file://my-url", JpsOrderRootType.COMPILED);