diff --git a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/AbstractNetwork.java b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/AbstractNetwork.java
index 21b69a6be..ecbbeace9 100644
--- a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/AbstractNetwork.java
+++ b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/AbstractNetwork.java
@@ -1,6 +1,5 @@
 package com.powsybl.network.store.iidm.impl;
 
-import com.google.common.collect.ImmutableList;
 import com.powsybl.iidm.network.*;
 import com.powsybl.network.store.model.IdentifiableAttributes;
 import com.powsybl.network.store.model.Resource;
diff --git a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkImpl.java b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkImpl.java
index d17bd8f03..ca0493f67 100644
--- a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkImpl.java
+++ b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkImpl.java
@@ -8,7 +8,6 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Lists;
-import com.google.common.collect.Multimap;
 import com.google.common.primitives.Ints;
 import com.powsybl.cgmes.extensions.*;
 import com.powsybl.commons.PowsyblException;
diff --git a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkObjectIndex.java b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkObjectIndex.java
index f6cd17908..694cf85db 100644
--- a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkObjectIndex.java
+++ b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkObjectIndex.java
@@ -1367,7 +1367,7 @@ void merge(NetworkObjectIndex other) {
         for (var generatorResource : other.generatorCache.allResourcesGetter.get()) {
             this.createGenerator(generatorResource);
         }
-        for (var batteryResource: other.batteryCache.allResourcesGetter.get()) {
+        for (var batteryResource : other.batteryCache.allResourcesGetter.get()) {
             this.createBattery(batteryResource);
         }
         for (var shuntResource : other.shuntCompensatorCache.allResourcesGetter.get()) {
diff --git a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkStoreClient.java b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkStoreClient.java
index dd327c295..1db1b736b 100644
--- a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkStoreClient.java
+++ b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/NetworkStoreClient.java
@@ -8,7 +8,6 @@
 package com.powsybl.network.store.iidm.impl;
 
 import com.powsybl.network.store.model.*;
-import org.openxmlformats.schemas.drawingml.x2006.chart.STHoleSizeUByte;
 
 import java.util.List;
 import java.util.Optional;
diff --git a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/SubnetworkImpl.java b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/SubnetworkImpl.java
index 9cafb5a92..ce3530446 100644
--- a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/SubnetworkImpl.java
+++ b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/SubnetworkImpl.java
@@ -63,7 +63,7 @@ public Stream<VoltageLevel> getVoltageLevelStream() {
 
     @Override
     public int getVoltageLevelCount() {
-        return (int)getVoltageLevelStream().count();
+        return (int) getVoltageLevelStream().count();
     }
 
     @Override
@@ -531,13 +531,13 @@ public Network detach() {
 
         // Move the substations and voltageLevels to the new network
         //ref.setRef(new RefObj<>(null));
-        for(Substation substation : getSubstations()) {
+        for (Substation substation : getSubstations()) {
             SubstationImpl impl = (SubstationImpl) substation;
             Resource< SubstationAttributes> attributes = impl.getResource();
             detachedNetwork.index.createSubstation(attributes);
             index.removeSubstation(attributes.getId());
         }
-        for(VoltageLevel vl : getVoltageLevels()) {
+        for (VoltageLevel vl : getVoltageLevels()) {
             VoltageLevelImpl impl = (VoltageLevelImpl) vl;
             Resource<VoltageLevelAttributes> attributes = impl.getResource();
             detachedNetwork.index.createVoltageLevel(attributes);
diff --git a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/VoltageLevelAdderImpl.java b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/VoltageLevelAdderImpl.java
index 1b3321716..0a2a9800b 100644
--- a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/VoltageLevelAdderImpl.java
+++ b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/VoltageLevelAdderImpl.java
@@ -41,7 +41,6 @@ class VoltageLevelAdderImpl extends AbstractIdentifiableAdder<VoltageLevelAdderI
         this.substationResource = substationResource;
     }
 
-
     @Override
     public VoltageLevelAdder setNominalV(double nominalV) {
         this.nominalV = nominalV;
diff --git a/network-store-iidm-impl/src/test/java/com/powsybl/network/store/iidm/impl/CreateNetworksUtil.java b/network-store-iidm-impl/src/test/java/com/powsybl/network/store/iidm/impl/CreateNetworksUtil.java
index 8dbceba7f..c9fcffdb2 100644
--- a/network-store-iidm-impl/src/test/java/com/powsybl/network/store/iidm/impl/CreateNetworksUtil.java
+++ b/network-store-iidm-impl/src/test/java/com/powsybl/network/store/iidm/impl/CreateNetworksUtil.java
@@ -637,6 +637,7 @@ static Network createBusBreakerNetworkWithOneBus(String networkSuffix) {
     static Network createBusBreakerNetworkWithTwoBuses() {
         return createBusBreakerNetworkWithTwoBuses("");
     }
+
     static Network createBusBreakerNetworkWithTwoBuses(String networkSuffix) {
         Network network = createBusBreakerNetworkWithOneBus(networkSuffix);
         VoltageLevel vl1 = network.getVoltageLevel("VL1" + networkSuffix);
@@ -645,7 +646,7 @@ static Network createBusBreakerNetworkWithTwoBuses(String networkSuffix) {
                 .add();
         vl1.getBusBreakerView().newSwitch()
                 .setId("BR1" + networkSuffix)
-                .setBus1("B2" +  networkSuffix)
+                .setBus1("B2" + networkSuffix)
                 .setBus2("B1" + networkSuffix)
                 .setOpen(false)
                 .add();
@@ -739,7 +740,7 @@ static Network createBusBreakerNetworkWithLine(String networkSuffix) {
                 .setId("B21" + networkSuffix)
                 .add();
         vl2.newGenerator()
-                .setId("G2" +  networkSuffix)
+                .setId("G2" + networkSuffix)
                 .setBus("B21" + networkSuffix)
                 .setMaxP(100.0)
                 .setMinP(50.0)
diff --git a/network-store-model/src/test/java/com/powsybl/network/store/model/ResourceTest.java b/network-store-model/src/test/java/com/powsybl/network/store/model/ResourceTest.java
index b3a069c1f..77ee00100 100644
--- a/network-store-model/src/test/java/com/powsybl/network/store/model/ResourceTest.java
+++ b/network-store-model/src/test/java/com/powsybl/network/store/model/ResourceTest.java
@@ -38,7 +38,7 @@ public void networkTest() throws IOException {
         ObjectMapper objectMapper = new ObjectMapper();
         objectMapper.registerModule(new JodaModule());
         String json = objectMapper.writeValueAsString(resource);
-        assertEquals("{\"type\":\"NETWORK\",\"id\":\"foo\",\"variantNum\":0,\"attributes\":{\"uuid\":\"7928181c-7977-4592-ba19-88027e4254e4\",\"fictitious\":false,\"caseDate\":1420070400000,\"forecastDistance\":0,\"connectedComponentsValid\":false,\"synchronousComponentsValid\":false}}", json);
+        assertEquals("{\"type\":\"NETWORK\",\"id\":\"foo\",\"parentNetwork\":null,\"variantNum\":0,\"attributes\":{\"uuid\":\"7928181c-7977-4592-ba19-88027e4254e4\",\"fictitious\":false,\"caseDate\":1420070400000,\"forecastDistance\":0,\"connectedComponentsValid\":false,\"synchronousComponentsValid\":false}}", json);
         Resource<NetworkAttributes> resource2 = objectMapper.readValue(json, new TypeReference<Resource<NetworkAttributes>>() { });
         assertNotNull(resource2);
         assertEquals("foo", resource2.getId());
@@ -61,7 +61,7 @@ public void substationTest() throws IOException {
         ObjectMapper objectMapper = JsonUtil.createObjectMapper();
         String json = objectMapper.writeValueAsString(resource);
 
-        String jsonRef = "{\"type\":\"SUBSTATION\",\"id\":\"S\",\"variantNum\":0,\"attributes\":{\"name\":\"SS\",\"fictitious\":false,\"country\":\"FR\",\"tso\":\"RTE\"}}";
+        String jsonRef = "{\"type\":\"SUBSTATION\",\"id\":\"S\",\"parentNetwork\":null,\"variantNum\":0,\"attributes\":{\"name\":\"SS\",\"fictitious\":false,\"country\":\"FR\",\"tso\":\"RTE\"}}";
         assertEquals(jsonRef, json);
 
         Resource<SubstationAttributes> resource2 = objectMapper.readValue(json, new TypeReference<Resource<SubstationAttributes>>() { });
diff --git a/network-store-model/src/test/java/com/powsybl/network/store/model/TopLevelDocumentTest.java b/network-store-model/src/test/java/com/powsybl/network/store/model/TopLevelDocumentTest.java
index 05745f767..62580387c 100644
--- a/network-store-model/src/test/java/com/powsybl/network/store/model/TopLevelDocumentTest.java
+++ b/network-store-model/src/test/java/com/powsybl/network/store/model/TopLevelDocumentTest.java
@@ -34,7 +34,7 @@ public void test() throws IOException {
         TopLevelDocument document = TopLevelDocument.of(resource);
         ObjectMapper objectMapper = JsonUtil.createObjectMapper();
         String json = objectMapper.writeValueAsString(document);
-        String jsonRef = "{\"data\":[{\"type\":\"SUBSTATION\",\"id\":\"S\",\"variantNum\":0,\"attributes\":{\"fictitious\":false,\"country\":\"FR\"}}],\"meta\":{}}";
+        String jsonRef = "{\"data\":[{\"type\":\"SUBSTATION\",\"id\":\"S\",\"parentNetwork\":null,\"variantNum\":0,\"attributes\":{\"fictitious\":false,\"country\":\"FR\"}}],\"meta\":{}}";
         assertEquals(jsonRef, json);
         TopLevelDocument document2 = objectMapper.readValue(json, TopLevelDocument.class);
         assertEquals(resource, document2.getData().get(0));
@@ -51,7 +51,7 @@ public void testMultiResources() throws IOException {
         TopLevelDocument document = TopLevelDocument.of(ImmutableList.of(resource, resource));
         ObjectMapper objectMapper = JsonUtil.createObjectMapper();
         String json = objectMapper.writeValueAsString(document);
-        String jsonRef = "{\"data\":[{\"type\":\"SUBSTATION\",\"id\":\"S\",\"variantNum\":0,\"attributes\":{\"fictitious\":false,\"country\":\"FR\"}},{\"type\":\"SUBSTATION\",\"id\":\"S\",\"variantNum\":0,\"attributes\":{\"fictitious\":false,\"country\":\"FR\"}}],\"meta\":{}}";
+        String jsonRef = "{\"data\":[{\"type\":\"SUBSTATION\",\"id\":\"S\",\"parentNetwork\":null,\"variantNum\":0,\"attributes\":{\"fictitious\":false,\"country\":\"FR\"}},{\"type\":\"SUBSTATION\",\"id\":\"S\",\"parentNetwork\":null,\"variantNum\":0,\"attributes\":{\"fictitious\":false,\"country\":\"FR\"}}],\"meta\":{}}";
         assertEquals(jsonRef, json);
         TopLevelDocument document2 = objectMapper.readValue(json, TopLevelDocument.class);
         assertEquals(2, document2.getData().size());
@@ -85,7 +85,7 @@ public void testGenerator() throws IOException {
         TopLevelDocument document = TopLevelDocument.of(resourceGenerator);
         ObjectMapper objectMapper = JsonUtil.createObjectMapper();
         String json = objectMapper.writeValueAsString(document);
-        String jsonRef = "{\"data\":[{\"type\":\"GENERATOR\",\"id\":\"gen1\",\"variantNum\":0,\"attributes\":{\"voltageLevelId\":\"vl1\",\"name\":\"name\",\"fictitious\":false,\"node\":1,\"bus\":\"bus1\",\"energySource\":\"HYDRO\",\"minP\":2.0,\"maxP\":1.0,\"voltageRegulatorOn\":false,\"targetP\":3.0,\"targetQ\":0.0,\"targetV\":4.0,\"ratedS\":0.0,\"p\":NaN,\"q\":NaN,\"regulatingTerminal\":{\"connectableId\":\"idEq\",\"side\":\"ONE\"}}}],\"meta\":{}}";
+        String jsonRef = "{\"data\":[{\"type\":\"GENERATOR\",\"id\":\"gen1\",\"parentNetwork\":null,\"variantNum\":0,\"attributes\":{\"voltageLevelId\":\"vl1\",\"name\":\"name\",\"fictitious\":false,\"node\":1,\"bus\":\"bus1\",\"energySource\":\"HYDRO\",\"minP\":2.0,\"maxP\":1.0,\"voltageRegulatorOn\":false,\"targetP\":3.0,\"targetQ\":0.0,\"targetV\":4.0,\"ratedS\":0.0,\"p\":NaN,\"q\":NaN,\"regulatingTerminal\":{\"connectableId\":\"idEq\",\"side\":\"ONE\"}}}],\"meta\":{}}";
         assertEquals(jsonRef, json);
         TopLevelDocument document2 = objectMapper.readValue(json, TopLevelDocument.class);
         assertEquals(resourceGenerator, document2.getData().get(0));