HONEYCOMB-270 Add isPresent() to Readers/Customizers

So that they can influence whether empty data is to be considered as present

+ Move registries implementations from util to impl
+ Introduce DelegatingReader trait
+ Extend GenericReader where possible to reduce duplication

Change-Id: I5a416acd0c4eab1fbc30fcbe585719991dbe9215
Signed-off-by: Maros Marsalek <mmarsale@cisco.com>

11 files changed, 1346 insertions, 26 deletions

diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericListReader.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericListReader.java
index ad93e8fe9..b06ac060f 100644
--- a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericListReader.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericListReader.java
@@ -25,7 +25,6 @@ import io.fd.honeycomb.translate.read.ReadContext;
 import io.fd.honeycomb.translate.read.ReadFailedException;
 import io.fd.honeycomb.translate.spi.read.ListReaderCustomizer;
 import io.fd.honeycomb.translate.util.RWUtils;
-import io.fd.honeycomb.translate.util.read.AbstractGenericReader;
 import java.util.ArrayList;
 import java.util.List;
 import javax.annotation.Nonnull;
@@ -48,12 +47,10 @@ import org.slf4j.LoggerFactory;
 @Beta
 @ThreadSafe
 public class GenericListReader<C extends DataObject & Identifiable<K>, K extends Identifier<C>, B extends Builder<C>>
-        extends AbstractGenericReader<C, B> implements ListReader<C, K, B> {
+        extends GenericReader<C, B> implements ListReader<C, K, B> {
 
     private static final Logger LOG = LoggerFactory.getLogger(GenericListReader.class);
 
-    protected final ListReaderCustomizer<C, K, B> customizer;
-
     /**
      * Create new {@link GenericListReader}
      *
@@ -62,8 +59,7 @@ public class GenericListReader<C extends DataObject & Identifiable<K>, K extends
      */
     public GenericListReader(@Nonnull final InstanceIdentifier<C> managedDataObjectType,
                              @Nonnull final ListReaderCustomizer<C, K, B> customizer) {
-        super(managedDataObjectType);
-        this.customizer = customizer;
+        super(managedDataObjectType, customizer);
     }
 
     @Override
@@ -92,31 +88,13 @@ public class GenericListReader<C extends DataObject & Identifiable<K>, K extends
     public List<K> getAllIds(@Nonnull final InstanceIdentifier<C> id, @Nonnull final ReadContext ctx)
             throws ReadFailedException {
         LOG.trace("{}: Getting all list ids", this);
-        final List<K> allIds = customizer.getAllIds(id, ctx);
+        final List<K> allIds = ((ListReaderCustomizer<C, K, B>) customizer).getAllIds(id, ctx);
         LOG.debug("{}: All list ids: {}", this, allIds);
         return allIds;
     }
 
     @Override
     public void merge(@Nonnull final Builder<? extends DataObject> builder, @Nonnull final List<C> readData) {
-        customizer.merge(builder, readData);
-    }
-
-    @Override
-    public void readCurrentAttributes(@Nonnull final InstanceIdentifier<C> id, @Nonnull final B builder,
-                                      @Nonnull final ReadContext ctx)
-            throws ReadFailedException {
-        try {
-            customizer.readCurrentAttributes(id, builder, ctx);
-        } catch (RuntimeException e) {
-            throw new ReadFailedException(id, e);
-        }
+        ((ListReaderCustomizer<C, K, B>) customizer).merge(builder, readData);
     }
-
-    @Nonnull
-    @Override
-    public B getBuilder(@Nonnull final InstanceIdentifier<C> id) {
-        return customizer.getBuilder(id);
-    }
-
 }
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericReader.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericReader.java
index e76b6e9a3..2bf439f82 100644
--- a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericReader.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericReader.java
@@ -22,6 +22,7 @@ import io.fd.honeycomb.translate.read.ReadFailedException;
 import io.fd.honeycomb.translate.read.Reader;
 import io.fd.honeycomb.translate.spi.read.ReaderCustomizer;
 import io.fd.honeycomb.translate.util.read.AbstractGenericReader;
+import io.fd.honeycomb.translate.util.read.ReflexiveReaderCustomizer;
 import javax.annotation.Nonnull;
 import javax.annotation.concurrent.ThreadSafe;
 import org.opendaylight.yangtools.concepts.Builder;
@@ -73,4 +74,14 @@ public class GenericReader<C extends DataObject, B extends Builder<C>>
         customizer.merge(parentBuilder, readValue);
     }
 
+    @Override
+    public boolean isPresent(final InstanceIdentifier<C> id, final C built, final ReadContext ctx)
+            throws ReadFailedException {
+        return customizer.isPresent(id, built, ctx);
+    }
+
+    public static <C extends DataObject, B extends Builder<C>> Reader<C, B> createReflexive(
+            final InstanceIdentifier<C> id, Class<B> builderClass) {
+        return new GenericReader<>(id, new ReflexiveReaderCustomizer<>(id.getTargetType(), builderClass));
+    }
 }
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReader.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReader.java
new file mode 100644
index 000000000..ec82b3f7f
--- /dev/null
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReader.java
@@ -0,0 +1,229 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.translate.impl.read.registry;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Optional;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Iterables;
+import io.fd.honeycomb.translate.read.InitFailedException;
+import io.fd.honeycomb.translate.read.InitListReader;
+import io.fd.honeycomb.translate.read.Initializer;
+import io.fd.honeycomb.translate.read.ListReader;
+import io.fd.honeycomb.translate.read.ReadContext;
+import io.fd.honeycomb.translate.read.ReadFailedException;
+import io.fd.honeycomb.translate.read.Reader;
+import io.fd.honeycomb.translate.util.RWUtils;
+import io.fd.honeycomb.translate.util.read.AbstractGenericReader;
+import io.fd.honeycomb.translate.util.read.DelegatingReader;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import javax.annotation.Nonnull;
+import org.opendaylight.controller.md.sal.binding.api.DataBroker;
+import org.opendaylight.yangtools.concepts.Builder;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.Identifiable;
+import org.opendaylight.yangtools.yang.binding.Identifier;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+class CompositeReader<D extends DataObject, B extends Builder<D>>
+        extends AbstractGenericReader<D, B>
+        implements Initializer<D>, DelegatingReader<D, B> {
+
+    private static final Logger LOG = LoggerFactory.getLogger(CompositeReader.class);
+
+    private final Reader<D, B> delegate;
+    private final ImmutableMap<Class<?>, Reader<? extends DataObject, ? extends Builder<?>>> childReaders;
+
+    private CompositeReader(final Reader<D, B> reader,
+                            final ImmutableMap<Class<?>, Reader<? extends DataObject, ? extends Builder<?>>> childReaders) {
+        super(reader.getManagedDataObjectType());
+        this.delegate = reader;
+        this.childReaders = childReaders;
+    }
+
+    @VisibleForTesting
+    ImmutableMap<Class<?>, Reader<? extends DataObject, ? extends Builder<?>>> getChildReaders() {
+        return childReaders;
+    }
+
+    @SuppressWarnings("unchecked")
+    public static <D extends DataObject> InstanceIdentifier<D> appendTypeToId(
+        final InstanceIdentifier<? extends DataObject> parentId, final InstanceIdentifier<D> type) {
+        final InstanceIdentifier.PathArgument t = new InstanceIdentifier.Item<>(type.getTargetType());
+        return (InstanceIdentifier<D>) InstanceIdentifier.create(Iterables.concat(
+            parentId.getPathArguments(), Collections.singleton(t)));
+    }
+
+    @Nonnull
+    @Override
+    public Optional<? extends DataObject> read(@Nonnull final InstanceIdentifier<? extends DataObject> id,
+                                               @Nonnull final ReadContext ctx) throws ReadFailedException {
+        if (shouldReadCurrent(id)) {
+            LOG.trace("{}: Reading current: {}", this, id);
+            return readCurrent((InstanceIdentifier<D>) id, ctx);
+        } else if (shouldDelegateToChild(id)) {
+            LOG.trace("{}: Reading child: {}", this, id);
+            return readSubtree(id, ctx);
+        } else {
+            // Fallback
+            LOG.trace("{}: Delegating read: {}", this, id);
+            return delegate.read(id, ctx);
+        }
+    }
+
+    private boolean shouldReadCurrent(@Nonnull final InstanceIdentifier<? extends DataObject> id) {
+        return id.getTargetType().equals(getManagedDataObjectType().getTargetType());
+    }
+
+    private boolean shouldDelegateToChild(@Nonnull final InstanceIdentifier<? extends DataObject> id) {
+        return childReaders.containsKey(RWUtils.getNextId(id, getManagedDataObjectType()).getType());
+    }
+
+    private Optional<? extends DataObject> readSubtree(final InstanceIdentifier<? extends DataObject> id,
+                                                       final ReadContext ctx) throws ReadFailedException {
+        final InstanceIdentifier.PathArgument nextId = RWUtils.getNextId(id, getManagedDataObjectType());
+        final Reader<?, ? extends Builder<?>> nextReader = childReaders.get(nextId.getType());
+        checkArgument(nextReader != null, "Unable to read: %s. No delegate present, available readers at next level: %s",
+                id, childReaders.keySet());
+        return nextReader.read(id, ctx);
+    }
+
+    @SuppressWarnings("unchecked")
+    private void readChildren(final InstanceIdentifier<D> id, @Nonnull final ReadContext ctx, final B builder)
+            throws ReadFailedException {
+        LOG.debug("{}: Reading children: {}", this, childReaders.keySet());
+        for (Reader child : childReaders.values()) {
+            final InstanceIdentifier childId = appendTypeToId(id, child.getManagedDataObjectType());
+
+            LOG.debug("{}: Reading child from: {}", this, child);
+            if (child instanceof ListReader) {
+                final List<? extends DataObject> list = ((ListReader) child).readList(childId, ctx);
+                // Dont set empty lists
+                if (!list.isEmpty()) {
+                    ((ListReader) child).merge(builder, list);
+                }
+            } else {
+                final Optional<? extends DataObject> read = child.read(childId, ctx);
+                if (read.isPresent()) {
+                    child.merge(builder, read.get());
+                }
+            }
+        }
+    }
+
+    @Override
+    public Reader<D, B> getDelegate() {
+        return delegate;
+    }
+
+    @Override
+    public void readCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final B builder,
+                                      @Nonnull final ReadContext ctx)
+            throws ReadFailedException {
+        delegate.readCurrentAttributes(id, builder, ctx);
+        readChildren(id, ctx, builder);
+    }
+
+    /**
+     * Wrap a Reader as a Composite Reader.
+     */
+    static <D extends DataObject, B extends Builder<D>> Reader<D, B> createForReader(
+            @Nonnull final Reader<D, B> reader,
+            @Nonnull final ImmutableMap<Class<?>, Reader<?, ? extends Builder<?>>> childReaders) {
+
+        return (reader instanceof ListReader)
+                ? new CompositeListReader<>((ListReader) reader, childReaders)
+                : new CompositeReader<>(reader, childReaders);
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public void init(final DataBroker broker, final InstanceIdentifier<D> id, final ReadContext ctx) throws InitFailedException {
+        if (delegate instanceof Initializer) {
+            LOG.trace("{}: Initializing current: {}", this, id);
+            ((Initializer<D>) delegate).init(broker, id, ctx);
+        }
+
+        for (Reader child : childReaders.values()) {
+            final InstanceIdentifier childId = appendTypeToId(id, child.getManagedDataObjectType());
+
+            if (child instanceof Initializer) {
+                LOG.trace("{}: Initializing child: {}", this, childId);
+                ((Initializer) child).init(broker, childId, ctx);
+            }
+        }
+    }
+
+    private static class CompositeListReader<D extends DataObject & Identifiable<K>, B extends Builder<D>, K extends Identifier<D>>
+            extends CompositeReader<D, B>
+            implements DelegatingListReader<D, K, B>, InitListReader<D, K, B> {
+
+        private final ListReader<D, K, B> delegate;
+
+        private CompositeListReader(final ListReader<D, K, B> reader,
+                                    final ImmutableMap<Class<?>, Reader<? extends DataObject, ? extends Builder<?>>> childReaders) {
+            super(reader, childReaders);
+            this.delegate = reader;
+        }
+
+        public ListReader<D, K, B> getDelegate() {
+            return delegate;
+        }
+
+        @Nonnull
+        @Override
+        public List<D> readList(@Nonnull final InstanceIdentifier<D> id, @Nonnull final ReadContext ctx)
+                throws ReadFailedException {
+            LOG.trace("{}: Reading all list entries", this);
+            final List<K> allIds = delegate.getAllIds(id, ctx);
+            LOG.debug("{}: Reading list entries for: {}", this, allIds);
+
+            // Override read list in order to perform readCurrent + readChildren here
+            final ArrayList<D> allEntries = new ArrayList<>(allIds.size());
+            for (K key : allIds) {
+                final InstanceIdentifier.IdentifiableItem<D, K> currentBdItem = RWUtils.getCurrentIdItem(id, key);
+                final InstanceIdentifier<D> keyedId = RWUtils.replaceLastInId(id, currentBdItem);
+                final Optional<D> read = readCurrent(keyedId, ctx);
+                if (read.isPresent()) {
+                    final DataObject singleItem = read.get();
+                    checkArgument(getManagedDataObjectType().getTargetType().isAssignableFrom(singleItem.getClass()));
+                    allEntries.add(getManagedDataObjectType().getTargetType().cast(singleItem));
+                }
+            }
+            return allEntries;
+        }
+
+        @Override
+        public void init(final DataBroker broker, final InstanceIdentifier<D> id, final ReadContext ctx)
+                throws InitFailedException {
+            try {
+                final List<K> allIds = delegate.getAllIds(id, ctx);
+                for (K key : allIds) {
+                    super.init(broker, RWUtils.replaceLastInId(id, RWUtils.getCurrentIdItem(id, key)), ctx);
+                }
+            } catch (ReadFailedException e) {
+                throw new InitFailedException(id, e);
+            }
+        }
+    }
+}
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistry.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistry.java
new file mode 100644
index 000000000..d69e53765
--- /dev/null
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistry.java
@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.translate.impl.read.registry;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Optional;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.LinkedListMultimap;
+import com.google.common.collect.Multimap;
+import io.fd.honeycomb.translate.read.InitFailedException;
+import io.fd.honeycomb.translate.read.Initializer;
+import io.fd.honeycomb.translate.read.ListReader;
+import io.fd.honeycomb.translate.read.ReadContext;
+import io.fd.honeycomb.translate.read.ReadFailedException;
+import io.fd.honeycomb.translate.read.Reader;
+import io.fd.honeycomb.translate.read.registry.ReaderRegistry;
+import io.fd.honeycomb.translate.util.RWUtils;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+import javax.annotation.Nonnull;
+import org.opendaylight.controller.md.sal.binding.api.DataBroker;
+import org.opendaylight.yangtools.concepts.Builder;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Simple reader registry able to perform and aggregated read (ROOT read) on top of all provided readers. Also able to
+ * delegate a specific read to one of the delegate readers.
+ * <p/>
+ * This could serve as a utility to hold & hide all available readers in upper layers.
+ */
+public final class CompositeReaderRegistry implements ReaderRegistry {
+
+    private static final Logger LOG = LoggerFactory.getLogger(CompositeReaderRegistry.class);
+
+    private final Map<Class<? extends DataObject>, Reader<? extends DataObject, ? extends Builder<?>>> rootReaders;
+
+    /**
+     * Create new {@link CompositeReaderRegistry}.
+     *
+     * @param rootReaders List of delegate readers
+     */
+    public CompositeReaderRegistry(@Nonnull final List<Reader<? extends DataObject, ? extends Builder<?>>> rootReaders) {
+        this.rootReaders = RWUtils.uniqueLinkedIndex(checkNotNull(rootReaders), RWUtils.MANAGER_CLASS_FUNCTION);
+    }
+
+    @VisibleForTesting
+    Map<Class<? extends DataObject>, Reader<? extends DataObject, ? extends Builder<?>>> getRootReaders() {
+        return rootReaders;
+    }
+
+    @Override
+    @Nonnull
+    public Multimap<InstanceIdentifier<? extends DataObject>, ? extends DataObject> readAll(
+        @Nonnull final ReadContext ctx) throws ReadFailedException {
+
+        LOG.debug("Reading from all delegates: {}", this);
+        LOG.trace("Reading from all delegates: {}", rootReaders.values());
+
+        final Multimap<InstanceIdentifier<? extends DataObject>, DataObject> objects = LinkedListMultimap.create();
+        for (Reader<? extends DataObject, ? extends Builder<?>> rootReader : rootReaders.values()) {
+            LOG.debug("Reading from delegate: {}", rootReader);
+
+            if (rootReader instanceof ListReader) {
+                final List<? extends DataObject> listEntries =
+                        ((ListReader) rootReader).readList(rootReader.getManagedDataObjectType(), ctx);
+                if (!listEntries.isEmpty()) {
+                    objects.putAll(rootReader.getManagedDataObjectType(), listEntries);
+                }
+            } else {
+                final Optional<? extends DataObject> read = rootReader.read(rootReader.getManagedDataObjectType(), ctx);
+                if (read.isPresent()) {
+                    objects.putAll(rootReader.getManagedDataObjectType(), Collections.singletonList(read.get()));
+                }
+            }
+        }
+
+        return objects;
+    }
+
+
+    @Override
+    public void initAll(@Nonnull final DataBroker broker, @Nonnull final ReadContext ctx) throws InitFailedException {
+        for (Reader<? extends DataObject, ? extends Builder<?>> rootReader : rootReaders.values()) {
+            if (rootReader instanceof Initializer<?>) {
+                ((Initializer) rootReader).init(broker, rootReader.getManagedDataObjectType(), ctx);
+            }
+        }
+    }
+
+    @Nonnull
+    @Override
+    public Optional<? extends DataObject> read(@Nonnull final InstanceIdentifier<? extends DataObject> id,
+                                               @Nonnull final ReadContext ctx)
+            throws ReadFailedException {
+        final InstanceIdentifier.PathArgument first = checkNotNull(
+                Iterables.getFirst(id.getPathArguments(), null), "Empty id");
+        final Reader<? extends DataObject, ? extends Builder<?>> reader = rootReaders.get(first.getType());
+        checkNotNull(reader,
+                "Unable to read %s. Missing reader. Current readers for: %s", id, rootReaders.keySet());
+        LOG.debug("Reading from delegate: {}", reader);
+        return reader.read(id, ctx);
+    }
+
+    @Override
+    public String toString() {
+        return getClass().getSimpleName()
+                + rootReaders.keySet().stream().map(Class::getSimpleName).collect(Collectors.toList());
+    }
+
+}
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistryBuilder.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistryBuilder.java
new file mode 100644
index 000000000..290c5d4aa
--- /dev/null
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistryBuilder.java
@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.translate.impl.read.registry;
+
+import com.google.common.collect.ImmutableMap;
+import io.fd.honeycomb.translate.impl.read.GenericReader;
+import io.fd.honeycomb.translate.read.InitReader;
+import io.fd.honeycomb.translate.read.Reader;
+import io.fd.honeycomb.translate.read.registry.ModifiableReaderRegistryBuilder;
+import io.fd.honeycomb.translate.read.registry.ReaderRegistry;
+import io.fd.honeycomb.translate.read.registry.ReaderRegistryBuilder;
+import io.fd.honeycomb.translate.util.AbstractSubtreeManagerRegistryBuilderBuilder;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+import javax.annotation.Nonnull;
+import javax.annotation.concurrent.NotThreadSafe;
+import org.opendaylight.yangtools.concepts.Builder;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+@NotThreadSafe
+public final class CompositeReaderRegistryBuilder
+        extends AbstractSubtreeManagerRegistryBuilderBuilder<Reader<? extends DataObject, ? extends Builder<?>>, ReaderRegistry>
+        implements ModifiableReaderRegistryBuilder, ReaderRegistryBuilder {
+
+    private static final Logger LOG = LoggerFactory.getLogger(CompositeReaderRegistryBuilder.class);
+
+    @Override
+    protected Reader<? extends DataObject, ? extends Builder<?>> getSubtreeHandler(@Nonnull final Set<InstanceIdentifier<?>> handledChildren,
+                                                                                   @Nonnull final Reader<? extends DataObject, ? extends Builder<?>> reader) {
+        return reader instanceof InitReader
+                ? InitSubtreeReader.createForReader(handledChildren, reader)
+                : SubtreeReader.createForReader(handledChildren, reader);
+    }
+
+    @Override
+    public <D extends DataObject> void addStructuralReader(@Nonnull InstanceIdentifier<D> id,
+                                                           @Nonnull Class<? extends Builder<D>> builderType) {
+        add(GenericReader.createReflexive(id, builderType));
+    }
+
+    /**
+     * Create {@link CompositeReaderRegistry} with Readers ordered according to submitted relationships.
+     * <p/>
+     * Note: The ordering only applies between nodes on the same level, inter-level and inter-subtree relationships are
+     * ignored.
+     */
+    @Override
+    public ReaderRegistry build() {
+        ImmutableMap<InstanceIdentifier<?>, Reader<? extends DataObject, ? extends Builder<?>>> mappedReaders =
+                getMappedHandlers();
+        LOG.debug("Building Reader registry with Readers: {}",
+                mappedReaders.keySet().stream()
+                        .map(InstanceIdentifier::getTargetType)
+                        .map(Class::getSimpleName)
+                        .collect(Collectors.joining(", ")));
+
+        LOG.trace("Building Reader registry with Readers: {}", mappedReaders);
+        final List<InstanceIdentifier<?>> readerOrder = new ArrayList<>(mappedReaders.keySet());
+
+        // Wrap readers into composite readers recursively, collect roots and create registry
+        final TypeHierarchy typeHierarchy = TypeHierarchy.create(mappedReaders.keySet());
+        final List<Reader<? extends DataObject, ? extends Builder<?>>> orderedRootReaders =
+                typeHierarchy.getRoots().stream()
+                        .map(rootId -> toCompositeReader(rootId, mappedReaders, typeHierarchy))
+                        .collect(Collectors.toList());
+
+        // We are violating the ordering from mappedReaders, since we are forming a composite structure
+        // but at least order root writers
+        orderedRootReaders.sort((reader1, reader2) -> readerOrder.indexOf(reader1.getManagedDataObjectType())
+                - readerOrder.indexOf(reader2.getManagedDataObjectType()));
+
+        return new CompositeReaderRegistry(orderedRootReaders);
+    }
+
+    private Reader<? extends DataObject, ? extends Builder<?>> toCompositeReader(
+            final InstanceIdentifier<?> instanceIdentifier,
+            final ImmutableMap<InstanceIdentifier<?>, Reader<? extends DataObject, ? extends Builder<?>>> mappedReaders,
+            final TypeHierarchy typeHierarchy) {
+
+        // Order child readers according to the mappedReadersCollection
+        final ImmutableMap.Builder<Class<?>, Reader<?, ? extends Builder<?>>> childReadersMapB = ImmutableMap.builder();
+        for (InstanceIdentifier<?> childId : mappedReaders.keySet()) {
+            if (typeHierarchy.getDirectChildren(instanceIdentifier).contains(childId)) {
+                childReadersMapB.put(childId.getTargetType(), toCompositeReader(childId, mappedReaders, typeHierarchy));
+            }
+        }
+
+        final ImmutableMap<Class<?>, Reader<?, ? extends Builder<?>>> childReadersMap = childReadersMapB.build();
+        return childReadersMap.isEmpty()
+                ? mappedReaders.get(instanceIdentifier)
+                : CompositeReader.createForReader(mappedReaders.get(instanceIdentifier), childReadersMap);
+    }
+}
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/InitSubtreeReader.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/InitSubtreeReader.java
new file mode 100644
index 000000000..809cdb214
--- /dev/null
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/InitSubtreeReader.java
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.translate.impl.read.registry;
+
+import io.fd.honeycomb.translate.read.InitFailedException;
+import io.fd.honeycomb.translate.read.InitListReader;
+import io.fd.honeycomb.translate.read.InitReader;
+import io.fd.honeycomb.translate.read.ListReader;
+import io.fd.honeycomb.translate.read.ReadContext;
+import io.fd.honeycomb.translate.read.Reader;
+import java.util.Set;
+import javax.annotation.Nonnull;
+import org.opendaylight.controller.md.sal.binding.api.DataBroker;
+import org.opendaylight.yangtools.concepts.Builder;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.Identifiable;
+import org.opendaylight.yangtools.yang.binding.Identifier;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+class InitSubtreeReader<O extends DataObject, B extends Builder<O>>
+        extends SubtreeReader<O, B>
+        implements InitReader<O, B> {
+
+    private InitSubtreeReader(final InitReader<O, B> delegate,
+                              final Set<InstanceIdentifier<?>> handledTypes) {
+        super(delegate, handledTypes);
+    }
+
+    @Override
+    public void init(final DataBroker broker, final InstanceIdentifier<O> id, final ReadContext ctx) throws InitFailedException {
+        ((InitReader<O, B>) delegate).init(broker, id, ctx);
+    }
+
+    /**
+     * Wrap a Reader as an initializing subtree Reader.
+     */
+    static <D extends DataObject, B extends Builder<D>> Reader<D, B> createForReader(@Nonnull final Set<InstanceIdentifier<?>> handledChildren,
+                                                                                     @Nonnull final Reader<D, B> reader) {
+        return (reader instanceof ListReader)
+                ? new InitSubtreeListReader<>((InitListReader) reader, handledChildren)
+                : new InitSubtreeReader<>(((InitReader<D, B>) reader), handledChildren);
+    }
+
+    private static class InitSubtreeListReader<D extends DataObject & Identifiable<K>, B extends Builder<D>, K extends Identifier<D>>
+            extends SubtreeListReader<D, B, K>
+            implements InitListReader<D, K, B> {
+
+        InitSubtreeListReader(final InitListReader<D, K, B> delegate,
+                              final Set<InstanceIdentifier<?>> handledTypes) {
+            super(delegate, handledTypes);
+        }
+
+        @Override
+        public void init(final DataBroker broker, final InstanceIdentifier<D> id, final ReadContext ctx) throws InitFailedException {
+            ((InitListReader<D, K, B>) delegate).init(broker, id, ctx);
+        }
+    }
+}
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/SubtreeReader.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/SubtreeReader.java
new file mode 100644
index 000000000..4db6dd70e
--- /dev/null
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/SubtreeReader.java
@@ -0,0 +1,216 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.translate.impl.read.registry;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.base.Optional;
+import com.google.common.collect.Iterables;
+import io.fd.honeycomb.translate.read.ListReader;
+import io.fd.honeycomb.translate.read.ReadContext;
+import io.fd.honeycomb.translate.read.ReadFailedException;
+import io.fd.honeycomb.translate.read.Reader;
+import io.fd.honeycomb.translate.util.RWUtils;
+import io.fd.honeycomb.translate.util.ReflectionUtils;
+import io.fd.honeycomb.translate.util.read.DelegatingReader;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import javax.annotation.Nonnull;
+import org.opendaylight.yangtools.concepts.Builder;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.Identifiable;
+import org.opendaylight.yangtools.yang.binding.Identifier;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Simple Reader delegate for subtree Readers (Readers handling also children nodes) providing a list of all the
+ * children nodes being handled.
+ */
+class SubtreeReader<D extends DataObject, B extends Builder<D>> implements DelegatingReader<D, B> {
+
+    private static final Logger LOG = LoggerFactory.getLogger(SubtreeReader.class);
+
+    protected final Reader<D, B> delegate;
+    private final Set<InstanceIdentifier<?>> handledChildTypes = new HashSet<>();
+
+    SubtreeReader(final Reader<D, B> delegate, Set<InstanceIdentifier<?>> handledTypes) {
+        this.delegate = delegate;
+        for (InstanceIdentifier<?> handledType : handledTypes) {
+            // Iid has to start with Reader's handled root type
+            checkArgument(delegate.getManagedDataObjectType().getTargetType().equals(
+                    handledType.getPathArguments().iterator().next().getType()),
+                    "Handled node from subtree has to be identified by an instance identifier starting from: %s."
+                            + "Instance identifier was: %s", getManagedDataObjectType().getTargetType(), handledType);
+            checkArgument(Iterables.size(handledType.getPathArguments()) > 1,
+                    "Handled node from subtree identifier too short: %s", handledType);
+            handledChildTypes.add(InstanceIdentifier.create(Iterables.concat(
+                    getManagedDataObjectType().getPathArguments(), Iterables.skip(handledType.getPathArguments(), 1))));
+        }
+    }
+
+    /**
+     * Return set of types also handled by this Reader. All of the types are children of the type managed by this Reader
+     * excluding the type of this Reader.
+     */
+    Set<InstanceIdentifier<?>> getHandledChildTypes() {
+        return handledChildTypes;
+    }
+
+    @Override
+    @Nonnull
+    public Optional<? extends DataObject> read(
+            @Nonnull final InstanceIdentifier<? extends DataObject> id,
+            @Nonnull final ReadContext ctx) throws ReadFailedException {
+        final InstanceIdentifier<?> wildcarded = RWUtils.makeIidWildcarded(id);
+
+        // Reading entire subtree and filtering if is current reader responsible
+        if (getHandledChildTypes().contains(wildcarded)) {
+            LOG.debug("{}: Subtree node managed by this writer requested: {}. Reading current and filtering", this, id);
+            // If there's no dedicated reader, use read current
+            final InstanceIdentifier<D> currentId = RWUtils.cutId(id, getManagedDataObjectType());
+            final Optional<? extends DataObject> current = delegate.read(currentId, ctx);
+            // then perform post-reading filtering (return only requested sub-node)
+            final Optional<? extends DataObject> readSubtree = current.isPresent()
+                ? filterSubtree(current.get(), id, getManagedDataObjectType().getTargetType())
+                : current;
+
+            LOG.debug("{}: Subtree: {} read successfully. Result: {}", this, id, readSubtree);
+            return readSubtree;
+
+        // If child that's handled here is not requested, then delegate should be able to handle the read
+        } else {
+            return delegate.read(id, ctx);
+        }
+    }
+
+    @Override
+    public Reader<D, B> getDelegate() {
+        return delegate;
+    }
+
+    @Nonnull
+    private static Optional<? extends DataObject> filterSubtree(@Nonnull final DataObject parent,
+                                                                @Nonnull final InstanceIdentifier<? extends DataObject> absolutPath,
+                                                                @Nonnull final Class<?> managedType) {
+        final InstanceIdentifier.PathArgument nextId =
+                RWUtils.getNextId(absolutPath, InstanceIdentifier.create(parent.getClass()));
+
+        final Optional<? extends DataObject> nextParent = findNextParent(parent, nextId, managedType);
+
+        if (Iterables.getLast(absolutPath.getPathArguments()).equals(nextId)) {
+            return nextParent; // we found the dataObject identified by absolutePath
+        } else if (nextParent.isPresent()) {
+            return filterSubtree(nextParent.get(), absolutPath, nextId.getType());
+        } else {
+            return nextParent; // we can't go further, return Optional.absent()
+        }
+    }
+
+    private static Optional<? extends DataObject> findNextParent(@Nonnull final DataObject parent,
+                                                                 @Nonnull final InstanceIdentifier.PathArgument nextId,
+                                                                 @Nonnull final Class<?> managedType) {
+        Optional<Method> method = ReflectionUtils.findMethodReflex(managedType, "get",
+                Collections.emptyList(), nextId.getType());
+
+        if (method.isPresent()) {
+            return Optional.fromNullable(filterSingle(parent, nextId, method.get()));
+        } else {
+            // List child nodes
+            method = ReflectionUtils.findMethodReflex(managedType,
+                    "get" + nextId.getType().getSimpleName(), Collections.emptyList(), List.class);
+
+            if (method.isPresent()) {
+                return filterList(parent, nextId, method.get());
+            } else {
+                throw new IllegalStateException(
+                        "Unable to filter " + nextId + " from " + parent + " getters not found using reflexion");
+            }
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Optional<? extends DataObject> filterList(final DataObject parent,
+                                                             final InstanceIdentifier.PathArgument nextId,
+                                                             final Method method) {
+        final List<? extends DataObject> invoke = (List<? extends DataObject>) invoke(method, nextId, parent);
+
+        checkArgument(nextId instanceof InstanceIdentifier.IdentifiableItem<?, ?>,
+                "Unable to perform wildcarded read for %s", nextId);
+        final Identifier key = ((InstanceIdentifier.IdentifiableItem) nextId).getKey();
+
+        final Method keyGetter = ReflectionUtils.findMethodReflex(nextId.getType(), "get",
+                        Collections.emptyList(), key.getClass()).get();
+
+        return Optional.fromNullable(invoke.stream()
+                .filter(item -> key.equals(invoke(keyGetter, nextId, item)))
+                .findFirst().orElse(null));
+    }
+
+    private static DataObject filterSingle(final DataObject parent,
+                                           final InstanceIdentifier.PathArgument nextId, final Method method) {
+        return nextId.getType().cast(invoke(method, nextId, parent));
+    }
+
+    private static Object invoke(final Method method,
+                                 final InstanceIdentifier.PathArgument nextId, final DataObject parent) {
+        try {
+            return method.invoke(parent);
+        } catch (IllegalAccessException | InvocationTargetException e) {
+            throw new IllegalArgumentException("Unable to get " + nextId + " from " + parent, e);
+        }
+    }
+
+    @Override
+    @Nonnull
+    public InstanceIdentifier<D> getManagedDataObjectType() {
+        return delegate.getManagedDataObjectType();
+    }
+
+    /**
+     * Wrap a Reader as a subtree Reader.
+     */
+    static <D extends DataObject, B extends Builder<D>> Reader<D, B> createForReader(@Nonnull final Set<InstanceIdentifier<?>> handledChildren,
+                                                                                     @Nonnull final Reader<D, B> reader) {
+        return (reader instanceof ListReader)
+                ? new SubtreeListReader<>((ListReader) reader, handledChildren)
+                : new SubtreeReader<>(reader, handledChildren);
+    }
+
+    static class SubtreeListReader<D extends DataObject & Identifiable<K>, B extends Builder<D>, K extends Identifier<D>>
+            extends SubtreeReader<D, B> implements DelegatingListReader<D, K, B>, ListReader<D, K, B> {
+
+        final ListReader<D, K, B> delegate;
+
+        SubtreeListReader(final ListReader<D, K, B> delegate,
+                                  final Set<InstanceIdentifier<?>> handledTypes) {
+            super(delegate, handledTypes);
+            this.delegate = delegate;
+        }
+
+        @Override
+        public ListReader<D, K, B> getDelegate() {
+            return delegate;
+        }
+    }
+
+}
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/TypeHierarchy.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/TypeHierarchy.java
new file mode 100644
index 000000000..14fc57632
--- /dev/null
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/TypeHierarchy.java
@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.translate.impl.read.registry;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.collect.Iterables;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+import javax.annotation.Nonnull;
+import org.jgrapht.experimental.dag.DirectedAcyclicGraph;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+final class TypeHierarchy {
+    private final DirectedAcyclicGraph<InstanceIdentifier<?>, Parent> hierarchy;
+
+    private TypeHierarchy(@Nonnull final DirectedAcyclicGraph<InstanceIdentifier<?>, Parent> hierarchy) {
+        this.hierarchy = hierarchy;
+    }
+
+    Set<InstanceIdentifier<?>> getAllChildren(InstanceIdentifier<?> id) {
+        final HashSet<InstanceIdentifier<?>> instanceIdentifiers = new HashSet<>();
+        for (InstanceIdentifier<?> childId : getDirectChildren(id)) {
+            instanceIdentifiers.add(childId);
+            instanceIdentifiers.addAll(getAllChildren(childId));
+        }
+        return instanceIdentifiers;
+    }
+
+    Set<InstanceIdentifier<?>> getDirectChildren(InstanceIdentifier<?> id) {
+        checkArgument(hierarchy.vertexSet().contains(id),
+                "Unknown reader: %s. Known readers: %s", id, hierarchy.vertexSet());
+
+        return hierarchy.outgoingEdgesOf(id).stream()
+                .map(hierarchy::getEdgeTarget)
+                .collect(Collectors.toSet());
+    }
+
+    Set<InstanceIdentifier<?>> getRoots() {
+        return hierarchy.vertexSet().stream()
+                .filter(vertex -> hierarchy.incomingEdgesOf(vertex).size() == 0)
+                .collect(Collectors.toSet());
+    }
+
+    /**
+     * Create reader hierarchy from a flat set of instance identifiers.
+     *
+     * @param allIds Set of unkeyed instance identifiers
+     */
+    static TypeHierarchy create(@Nonnull Set<InstanceIdentifier<?>> allIds) {
+        final DirectedAcyclicGraph<InstanceIdentifier<?>, Parent>
+                readersHierarchy = new DirectedAcyclicGraph<>((sourceVertex, targetVertex) -> new Parent());
+
+        for (InstanceIdentifier<?> allId : allIds) {
+            checkArgument(!Iterables.isEmpty(allId.getPathArguments()), "Empty ID detected");
+
+            if (Iterables.size(allId.getPathArguments()) == 1) {
+                readersHierarchy.addVertex(allId);
+            }
+
+            List<InstanceIdentifier.PathArgument> pathArgs = new LinkedList<>();
+            pathArgs.add(allId.getPathArguments().iterator().next());
+
+            for (InstanceIdentifier.PathArgument pathArgument : Iterables.skip(allId.getPathArguments(), 1)) {
+                final InstanceIdentifier<?> previous = InstanceIdentifier.create(pathArgs);
+                pathArgs.add(pathArgument);
+                final InstanceIdentifier<?> current = InstanceIdentifier.create(pathArgs);
+
+                readersHierarchy.addVertex(previous);
+                readersHierarchy.addVertex(current);
+
+                try {
+                    readersHierarchy.addDagEdge(previous, current);
+                } catch (DirectedAcyclicGraph.CycleFoundException e) {
+                    throw new IllegalArgumentException("Loop in hierarchy detected", e);
+                }
+            }
+        }
+
+        return new TypeHierarchy(readersHierarchy);
+    }
+
+    private static final class Parent{}
+}
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistry.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistry.java
new file mode 100644
index 000000000..990431a15
--- /dev/null
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistry.java
@@ -0,0 +1,314 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.translate.impl.write.registry;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+import static io.fd.honeycomb.translate.util.RWUtils.makeIidWildcarded;
+
+import com.google.common.base.Optional;
+import com.google.common.collect.HashMultimap;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Multimap;
+import com.google.common.collect.Sets;
+import io.fd.honeycomb.translate.TranslationException;
+import io.fd.honeycomb.translate.util.RWUtils;
+import io.fd.honeycomb.translate.write.DataObjectUpdate;
+import io.fd.honeycomb.translate.write.WriteContext;
+import io.fd.honeycomb.translate.write.WriteFailedException;
+import io.fd.honeycomb.translate.write.Writer;
+import io.fd.honeycomb.translate.write.registry.WriterRegistry;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.ThreadSafe;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Flat writer registry, delegating updates to writers in the order writers were submitted.
+ */
+@ThreadSafe
+final class FlatWriterRegistry implements WriterRegistry {
+
+    private static final Logger LOG = LoggerFactory.getLogger(FlatWriterRegistry.class);
+
+    // All types handled by writers directly or as children
+    private final ImmutableSet<InstanceIdentifier<?>> handledTypes;
+
+    private final Set<InstanceIdentifier<?>> writersOrderReversed;
+    private final Set<InstanceIdentifier<?>> writersOrder;
+    private final Map<InstanceIdentifier<?>, Writer<?>> writers;
+
+    /**
+     * Create flat registry instance.
+     *
+     * @param writers immutable, ordered map of writers to use to process updates. Order of the writers has to be
+     *                one in which create and update operations should be handled. Deletes will be handled in reversed
+     *                order. All deletes are handled before handling all the updates.
+     */
+    FlatWriterRegistry(@Nonnull final ImmutableMap<InstanceIdentifier<?>, Writer<?>> writers) {
+        this.writers = writers;
+        this.writersOrderReversed = Sets.newLinkedHashSet(Lists.reverse(Lists.newArrayList(writers.keySet())));
+        this.writersOrder = writers.keySet();
+        this.handledTypes = getAllHandledTypes(writers);
+    }
+
+    private static ImmutableSet<InstanceIdentifier<?>> getAllHandledTypes(
+            @Nonnull final ImmutableMap<InstanceIdentifier<?>, Writer<?>> writers) {
+        final ImmutableSet.Builder<InstanceIdentifier<?>> handledTypesBuilder = ImmutableSet.builder();
+        for (Map.Entry<InstanceIdentifier<?>, Writer<?>> writerEntry : writers.entrySet()) {
+            final InstanceIdentifier<?> writerType = writerEntry.getKey();
+            final Writer<?> writer = writerEntry.getValue();
+            handledTypesBuilder.add(writerType);
+            if (writer instanceof SubtreeWriter) {
+                handledTypesBuilder.addAll(((SubtreeWriter<?>) writer).getHandledChildTypes());
+            }
+        }
+        return handledTypesBuilder.build();
+    }
+
+    @Override
+    public void update(@Nonnull final DataObjectUpdates updates,
+                       @Nonnull final WriteContext ctx) throws TranslationException {
+        if (updates.isEmpty()) {
+            return;
+        }
+
+        // Optimization
+        if (updates.containsOnlySingleType()) {
+            // First process delete
+            singleUpdate(updates.getDeletes(), ctx);
+            // Next is update
+            singleUpdate(updates.getUpdates(), ctx);
+        } else {
+            // First process deletes
+            bulkUpdate(updates.getDeletes(), ctx, true, writersOrderReversed);
+            // Next are updates
+            bulkUpdate(updates.getUpdates(), ctx, true, writersOrder);
+        }
+
+        LOG.debug("Update successful for types: {}", updates.getTypeIntersection());
+        LOG.trace("Update successful for: {}", updates);
+    }
+
+    private void singleUpdate(@Nonnull final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates,
+                              @Nonnull final WriteContext ctx) throws WriteFailedException {
+        if (updates.isEmpty()) {
+            return;
+        }
+
+        final InstanceIdentifier<?> singleType = updates.keySet().iterator().next();
+        LOG.debug("Performing single type update for: {}", singleType);
+        Collection<? extends DataObjectUpdate> singleTypeUpdates = updates.get(singleType);
+        Writer<?> writer = getWriter(singleType);
+
+        if (writer == null) {
+            // This node must be handled by a subtree writer, find it and call it or else fail
+            checkArgument(handledTypes.contains(singleType), "Unable to process update. Missing writers for: %s",
+                    singleType);
+            writer = getSubtreeWriterResponsible(singleType);
+            singleTypeUpdates = getParentDataObjectUpdate(ctx, updates, writer);
+        }
+
+        LOG.trace("Performing single type update with writer: {}", writer);
+        for (DataObjectUpdate singleUpdate : singleTypeUpdates) {
+            writer.update(singleUpdate.getId(), singleUpdate.getDataBefore(), singleUpdate.getDataAfter(), ctx);
+        }
+    }
+
+    private Writer<?> getSubtreeWriterResponsible(final InstanceIdentifier<?> singleType) {
+        return writers.values().stream()
+                .filter(w -> w instanceof SubtreeWriter)
+                .filter(w -> ((SubtreeWriter<?>) w).getHandledChildTypes().contains(singleType))
+                .findFirst()
+                .get();
+    }
+
+    private Collection<DataObjectUpdate> getParentDataObjectUpdate(final WriteContext ctx,
+                                                                   final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates,
+                                                                   final Writer<?> writer) {
+        // Now read data for subtree reader root, but first keyed ID is needed and that ID can be cut from updates
+        InstanceIdentifier<?> firstAffectedChildId = ((SubtreeWriter<?>) writer).getHandledChildTypes().stream()
+                .filter(updates::containsKey)
+                .map(unkeyedId -> updates.get(unkeyedId))
+                .flatMap(doUpdates -> doUpdates.stream())
+                .map(DataObjectUpdate::getId)
+                .findFirst()
+                .get();
+
+        final InstanceIdentifier<?> parentKeyedId =
+                RWUtils.cutId(firstAffectedChildId, writer.getManagedDataObjectType());
+
+        final Optional<? extends DataObject> parentBefore = ctx.readBefore(parentKeyedId);
+        final Optional<? extends DataObject> parentAfter = ctx.readAfter(parentKeyedId);
+        return Collections.singleton(
+                DataObjectUpdate.create(parentKeyedId, parentBefore.orNull(), parentAfter.orNull()));
+    }
+
+    private void bulkUpdate(@Nonnull final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates,
+                            @Nonnull final WriteContext ctx,
+                            final boolean attemptRevert,
+                            @Nonnull final Set<InstanceIdentifier<?>> writersOrder) throws BulkUpdateException {
+        if (updates.isEmpty()) {
+            return;
+        }
+
+        LOG.debug("Performing bulk update with revert attempt: {} for: {}", attemptRevert, updates.keySet());
+
+        // Check that all updates can be handled
+        checkAllTypesCanBeHandled(updates);
+
+        // Capture all changes successfully processed in case revert is needed
+        final Set<InstanceIdentifier<?>> processedNodes = new HashSet<>();
+
+        // Iterate over all writers and call update if there are any related updates
+        for (InstanceIdentifier<?> writerType : writersOrder) {
+            Collection<? extends DataObjectUpdate> writersData = updates.get(writerType);
+            final Writer<?> writer = getWriter(writerType);
+
+            if (writersData.isEmpty()) {
+                // If there are no data for current writer, but it is a SubtreeWriter and there are updates to
+                // its children, still invoke it with its root data
+                if (writer instanceof SubtreeWriter<?> && isAffected(((SubtreeWriter<?>) writer), updates)) {
+                    // Provide parent data for SubtreeWriter for further processing
+                    writersData = getParentDataObjectUpdate(ctx, updates, writer);
+                } else {
+                    // Skipping unaffected writer
+                    // Alternative to this would be modification sort according to the order of writers
+                    continue;
+                }
+            }
+
+            LOG.debug("Performing update for: {}",  writerType);
+            LOG.trace("Performing update with writer: {}", writer);
+
+            for (DataObjectUpdate singleUpdate : writersData) {
+                try {
+                    writer.update(singleUpdate.getId(), singleUpdate.getDataBefore(), singleUpdate.getDataAfter(), ctx);
+                    processedNodes.add(singleUpdate.getId());
+                    LOG.trace("Update successful for type: {}", writerType);
+                    LOG.debug("Update successful for: {}", singleUpdate);
+                } catch (Exception e) {
+                    // do not log this exception here,its logged in ModifiableDataTreeDelegator
+
+                    final Reverter reverter = attemptRevert
+                            ? new ReverterImpl(processedNodes, updates, writersOrder)
+                            : (final WriteContext writeContext) -> {};//NOOP reverter
+
+                    // Find out which changes left unprocessed
+                    final Set<InstanceIdentifier<?>> unprocessedChanges = updates.values().stream()
+                            .map(DataObjectUpdate::getId)
+                            .filter(id -> !processedNodes.contains(id))
+                            .collect(Collectors.toSet());
+                    throw new BulkUpdateException(unprocessedChanges, reverter, e);
+                }
+            }
+        }
+    }
+
+    private void checkAllTypesCanBeHandled(
+            @Nonnull final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates) {
+        if (!handledTypes.containsAll(updates.keySet())) {
+            final Sets.SetView<InstanceIdentifier<?>> missingWriters = Sets.difference(updates.keySet(), handledTypes);
+            LOG.warn("Unable to process update. Missing writers for: {}", missingWriters);
+            throw new IllegalArgumentException("Unable to process update. Missing writers for: " + missingWriters);
+        }
+    }
+
+    /**
+     * Check whether {@link SubtreeWriter} is affected by the updates.
+     *
+     * @return true if there are any updates to SubtreeWriter's child nodes (those marked by SubtreeWriter
+     *         as being taken care of)
+     * */
+    private static boolean isAffected(final SubtreeWriter<?> writer,
+                               final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates) {
+        return !Sets.intersection(writer.getHandledChildTypes(), updates.keySet()).isEmpty();
+    }
+
+    @Nullable
+    private Writer<?> getWriter(@Nonnull final InstanceIdentifier<?> singleType) {
+        return writers.get(singleType);
+    }
+
+    private final class ReverterImpl implements Reverter {
+
+        private final Collection<InstanceIdentifier<?>> processedNodes;
+        private final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates;
+        private final Set<InstanceIdentifier<?>> revertDeleteOrder;
+
+        ReverterImpl(final Collection<InstanceIdentifier<?>> processedNodes,
+                     final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates,
+                     final Set<InstanceIdentifier<?>> writersOrderOriginal) {
+            this.processedNodes = processedNodes;
+            this.updates = updates;
+            // Use opposite ordering when executing revert
+            this.revertDeleteOrder =  writersOrderOriginal == FlatWriterRegistry.this.writersOrder
+                    ? FlatWriterRegistry.this.writersOrderReversed
+                    : FlatWriterRegistry.this.writersOrder;
+        }
+
+        @Override
+        public void revert(@Nonnull final WriteContext writeContext) throws RevertFailedException {
+            checkNotNull(writeContext, "Cannot revert changes for null context");
+
+            Multimap<InstanceIdentifier<?>, DataObjectUpdate> updatesToRevert =
+                    filterAndRevertProcessed(updates, processedNodes);
+
+            LOG.info("Attempting revert for changes: {}", updatesToRevert);
+            try {
+                // Perform reversed bulk update without revert attempt
+                bulkUpdate(updatesToRevert, writeContext, true, revertDeleteOrder);
+                LOG.info("Revert successful");
+            } catch (BulkUpdateException e) {
+                LOG.error("Revert failed", e);
+                throw new RevertFailedException(e.getFailedIds(), e);
+            }
+        }
+
+        /**
+         * Create new updates map, but only keep already processed changes. Switching before and after data for each
+         * update.
+         */
+        private Multimap<InstanceIdentifier<?>, DataObjectUpdate> filterAndRevertProcessed(
+                final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates,
+                final Collection<InstanceIdentifier<?>> processedNodes) {
+            final Multimap<InstanceIdentifier<?>, DataObjectUpdate> filtered = HashMultimap.create();
+            for (InstanceIdentifier<?> processedNode : processedNodes) {
+                final InstanceIdentifier<?> wildcardedIid = makeIidWildcarded(processedNode);
+                if (updates.containsKey(wildcardedIid)) {
+                    updates.get(wildcardedIid).stream()
+                            .filter(dataObjectUpdate -> processedNode.contains(dataObjectUpdate.getId()))
+                            // putting under unkeyed identifier, to prevent failing of checkAllTypesCanBeHandled
+                            .forEach(dataObjectUpdate -> filtered.put(wildcardedIid, dataObjectUpdate.reverse()));
+                }
+            }
+            return filtered;
+        }
+    }
+
+}
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistryBuilder.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistryBuilder.java
new file mode 100644
index 000000000..936aa3c1e
--- /dev/null
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistryBuilder.java
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.translate.impl.write.registry;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableMap;
+import io.fd.honeycomb.translate.write.registry.WriterRegistryBuilder;
+import io.fd.honeycomb.translate.util.AbstractSubtreeManagerRegistryBuilderBuilder;
+import io.fd.honeycomb.translate.write.Writer;
+import io.fd.honeycomb.translate.write.registry.ModifiableWriterRegistryBuilder;
+import io.fd.honeycomb.translate.write.registry.WriterRegistry;
+import java.util.Set;
+import java.util.stream.Collectors;
+import javax.annotation.Nonnull;
+import javax.annotation.concurrent.NotThreadSafe;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Builder for {@link FlatWriterRegistry} allowing users to specify inter-writer relationships.
+ */
+@NotThreadSafe
+public final class FlatWriterRegistryBuilder
+        extends AbstractSubtreeManagerRegistryBuilderBuilder<Writer<? extends DataObject>, WriterRegistry>
+        implements ModifiableWriterRegistryBuilder, WriterRegistryBuilder {
+
+    private static final Logger LOG = LoggerFactory.getLogger(FlatWriterRegistryBuilder.class);
+
+    @Override
+    protected Writer<? extends DataObject> getSubtreeHandler(final @Nonnull Set<InstanceIdentifier<?>> handledChildren,
+                                                             final @Nonnull Writer<? extends DataObject> writer) {
+        return SubtreeWriter.createForWriter(handledChildren, writer);
+    }
+
+    /**
+     * Create FlatWriterRegistry with writers ordered according to submitted relationships.
+     */
+    @Override
+    public WriterRegistry build() {
+        final ImmutableMap<InstanceIdentifier<?>, Writer<?>> mappedWriters = getMappedHandlers();
+        LOG.debug("Building writer registry with writers: {}",
+                mappedWriters.keySet().stream()
+                        .map(InstanceIdentifier::getTargetType)
+                        .map(Class::getSimpleName)
+                        .collect(Collectors.joining(", ")));
+        LOG.trace("Building writer registry with writers: {}", mappedWriters);
+        return new FlatWriterRegistry(mappedWriters);
+    }
+
+    @VisibleForTesting
+    @Override
+    protected ImmutableMap<InstanceIdentifier<?>, Writer<? extends DataObject>> getMappedHandlers() {
+        return super.getMappedHandlers();
+    }
+}
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/SubtreeWriter.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/SubtreeWriter.java
new file mode 100644
index 000000000..fc6ecc67e
--- /dev/null
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/SubtreeWriter.java
@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.translate.impl.write.registry;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.collect.Iterables;
+import io.fd.honeycomb.translate.write.WriteContext;
+import io.fd.honeycomb.translate.write.WriteFailedException;
+import io.fd.honeycomb.translate.write.Writer;
+import java.util.HashSet;
+import java.util.Set;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+/**
+ * Simple writer delegate for subtree writers (writers handling also children nodes) providing a list of all the
+ * children nodes being handled.
+ */
+final class SubtreeWriter<D extends DataObject> implements Writer<D> {
+
+    private final Writer<D> delegate;
+    private final Set<InstanceIdentifier<?>> handledChildTypes = new HashSet<>();
+
+    private SubtreeWriter(final Writer<D> delegate, Set<InstanceIdentifier<?>> handledTypes) {
+        this.delegate = delegate;
+        for (InstanceIdentifier<?> handledType : handledTypes) {
+            // Iid has to start with writer's handled root type
+            checkArgument(delegate.getManagedDataObjectType().getTargetType().equals(
+                    handledType.getPathArguments().iterator().next().getType()),
+                    "Handled node from subtree has to be identified by an instance identifier starting from: %s."
+                    + "Instance identifier was: %s", getManagedDataObjectType().getTargetType(), handledType);
+            checkArgument(Iterables.size(handledType.getPathArguments()) > 1,
+                    "Handled node from subtree identifier too short: %s", handledType);
+            handledChildTypes.add(InstanceIdentifier.create(Iterables.concat(
+                    getManagedDataObjectType().getPathArguments(), Iterables.skip(handledType.getPathArguments(), 1))));
+        }
+    }
+
+    /**
+     * Return set of types also handled by this writer. All of the types are children of the type managed by this
+     * writer excluding the type of this writer.
+     */
+    Set<InstanceIdentifier<?>> getHandledChildTypes() {
+        return handledChildTypes;
+    }
+
+    @Override
+    public void update(
+            @Nonnull final InstanceIdentifier<? extends DataObject> id,
+            @Nullable final DataObject dataBefore,
+            @Nullable final DataObject dataAfter, @Nonnull final WriteContext ctx) throws WriteFailedException {
+        delegate.update(id, dataBefore, dataAfter, ctx);
+    }
+
+    @Override
+    @Nonnull
+    public InstanceIdentifier<D> getManagedDataObjectType() {
+        return delegate.getManagedDataObjectType();
+    }
+
+    /**
+     * Wrap a writer as a subtree writer.
+     */
+    static Writer<?> createForWriter(@Nonnull final Set<InstanceIdentifier<?>> handledChildren,
+                                     @Nonnull final Writer<? extends DataObject> writer) {
+        return new SubtreeWriter<>(writer, handledChildren);
+    }
+}