diff --git a/api/server/src/main/java/org/softwareheritage/graph/Graph.java b/api/server/src/main/java/org/softwareheritage/graph/Graph.java
index 49a9a11..cbbd03b 100644
--- a/api/server/src/main/java/org/softwareheritage/graph/Graph.java
+++ b/api/server/src/main/java/org/softwareheritage/graph/Graph.java
@@ -1,97 +1,46 @@
 package org.softwareheritage.graph;
 
-import java.io.FileInputStream;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.InputStreamReader;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.zip.GZIPInputStream;
-
 import it.unimi.dsi.big.webgraph.BVGraph;
 import it.unimi.dsi.big.webgraph.LazyLongIterator;
-import it.unimi.dsi.fastutil.io.BinIO;
-import it.unimi.dsi.fastutil.longs.LongBigArrays;
-import it.unimi.dsi.fastutil.objects.Object2LongFunction;
-import it.unimi.dsi.io.FastBufferedReader;
-import it.unimi.dsi.io.LineIterator;
-import it.unimi.dsi.lang.MutableString;
+
+import org.softwareheritage.graph.NodeIdMap;
 
 public class Graph {
   BVGraph graph;
   String path;
-  HashMap<String, Long> hashToNode;
-  HashMap<Long, String> nodeToHash;
+  NodeIdMap nodeIdMap;
 
   public Graph(String graphPath) throws Exception {
     this.graph = BVGraph.load(graphPath);
     this.path = graphPath;
-    this.hashToNode = new HashMap<String, Long>();
-    this.nodeToHash = new HashMap<Long, String>();
-    setupNodesMapping();
-  }
-
-  private void setupNodesMapping() throws IOException, ClassNotFoundException {
-    // First mapping: SWH hexhash (strings) <=> WebGraph MPH (longs)
-    HashMap<Long, String> mphToHash = new HashMap<Long, String>();
-    @SuppressWarnings("unchecked")
-    Object2LongFunction<String> mphMap =
-        (Object2LongFunction<String>) BinIO.loadObject(path + ".mph");
-
-    InputStream nodeFile = new GZIPInputStream(new FileInputStream(path + ".nodes.csv.gz"));
-    Collection<MutableString> hashes =
-        new LineIterator(new FastBufferedReader(new InputStreamReader(nodeFile, "UTF-8")))
-            .allLines();
-
-    for (MutableString h : hashes) {
-      String hash = new String(h.toString());
-      long mph = mphMap.getLong(hash);
-      mphToHash.put(mph, hash);
-    }
-
-    // Second mapping: WebGraph MPH (longs) <=> BFS ordering (longs)
-    long n = mphMap.size();
-    long[][] bfsMap = LongBigArrays.newBigArray(n);
-    long loaded = BinIO.loadLongs(path + ".order", bfsMap);
-    if (loaded != n) {
-      throw new IllegalArgumentException("Graph contains " + n + " nodes, but read " + loaded);
-    }
-
-    // Create final mapping: SWH hexhash (strings) <=> BFS ordering (longs)
-    for (long id = 0; id < n; id++) {
-      String hash = mphToHash.get(id);
-      long node = LongBigArrays.get(bfsMap, id);
-
-      hashToNode.put(hash, node);
-      nodeToHash.put(node, hash);
-    }
+    this.nodeIdMap = new NodeIdMap(graphPath);
   }
 
   public String getPath() {
     return path;
   }
 
   public long getNode(String hash) {
-    return hashToNode.get(hash);
+    return nodeIdMap.getNode(hash);
   }
 
   public String getHash(long node) {
-    return nodeToHash.get(node);
+    return nodeIdMap.getHash(node);
   }
 
   public long getNbNodes() {
     return graph.numNodes();
   }
 
   public long getNbEdges() {
     return graph.numArcs();
   }
 
   public LazyLongIterator successors(long node) {
     return graph.successors(node);
   }
 
   public long outdegree(long node) {
     return graph.outdegree(node);
   }
 }
diff --git a/api/server/src/main/java/org/softwareheritage/graph/NodeIdMap.java b/api/server/src/main/java/org/softwareheritage/graph/NodeIdMap.java
new file mode 100644
index 0000000..65884e5
--- /dev/null
+++ b/api/server/src/main/java/org/softwareheritage/graph/NodeIdMap.java
@@ -0,0 +1,21 @@
+package org.softwareheritage.graph;
+
+// TODO: decide on how to do the disk-based node id map
+public class NodeIdMap {
+  String graphPath;
+
+  public NodeIdMap(String graphPath) {
+    this.graphPath = graphPath;
+  }
+
+  public long getNode(String hash) {
+    return 42;
+  }
+
+  public String getHash(long node) {
+    return null;
+  }
+
+  public void dump() {
+  }
+}