diff --git a/core/metaschema b/core/metaschema
index e54d01d0a..88e050a9e 160000
--- a/core/metaschema
+++ b/core/metaschema
@@ -1 +1 @@
-Subproject commit e54d01d0a1332ed792c57b794ed8a7dbdee16a9d
+Subproject commit 88e050a9e2b1ed7c158f35f4f5468e01e0e76d88
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/IAssemblyDefinition.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/IAssemblyDefinition.java
index fd24a38d6..4d0d07381 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/IAssemblyDefinition.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/IAssemblyDefinition.java
@@ -49,6 +49,15 @@ public interface IAssemblyDefinition
    */
   String getRootName();
 
+  /**
+   * Get the root index to use for binary data, if this assembly is a top-level
+   * root.
+   *
+   * @return the root index if provided and this assembly is a top-level root, or
+   *         {@code null} otherwise
+   */
+  Integer getRootIndex();
+
   /**
    * Get the XML qualified name to use in XML as the root element.
    *
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/INamedInstance.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/INamedInstance.java
index 5117c97df..0e04cd093 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/INamedInstance.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/INamedInstance.java
@@ -31,6 +31,7 @@
 import javax.xml.namespace.QName;
 
 import edu.umd.cs.findbugs.annotations.NonNull;
+import edu.umd.cs.findbugs.annotations.Nullable;
 
 /**
  * This marker interface indicates that the instance has a flag, field, or
@@ -104,6 +105,12 @@ default String toCoordinates() {
         definition.isInline() ? 0 : definition.hashCode());
   }
 
+  @Override
+  default Integer getIndex() {
+    // does not have an index
+    return null;
+  }
+
   @Override
   @NonNull
   default String getEffectiveName() {
@@ -116,6 +123,18 @@ default String getEffectiveName() {
     return result;
   }
 
+  @Override
+  @Nullable
+  default Integer getEffectiveIndex() {
+    Integer result = getUseIndex();
+    if (result == null) {
+      // fall back to the definition
+      IDefinition def = getDefinition();
+      result = def.getEffectiveIndex();
+    }
+    return result;
+  }
+
   @Override
   default String getEffectiveFormalName() {
     String result = getFormalName();
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/INamedModelElement.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/INamedModelElement.java
index 3e670ed2d..41516c373 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/INamedModelElement.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/INamedModelElement.java
@@ -155,6 +155,22 @@ default String getJsonName() {
     return getEffectiveName();
   }
 
+  /**
+   * Retrieve the name of the model element.
+   *
+   * @return the name
+   */
+  @NonNull
+  String getName();
+
+  /**
+   * Retrieve the name to use for the model element, instead of the name.
+   *
+   * @return the use name or {@code null} if no use name is defined
+   */
+  @Nullable
+  String getUseName();
+
   /**
    * Get the name to use based on the provided names. This method will return the
    * use name provided by {@link #getUseName()} if the call is not {@code null},
@@ -174,18 +190,24 @@ default String getEffectiveName() {
   }
 
   /**
-   * Retrieve the name of the model element.
+   * Retrieve the index value to use for binary naming.
    *
-   * @return the name
+   * @return the name index or {@code null} if no name index is defined
    */
-  @NonNull
-  String getName();
+  @Nullable
+  Integer getIndex();
 
   /**
-   * Retrieve the name to use for the model element, instead of the name.
+   * Retrieve the index value to use for binary naming, instead of the name.
    *
-   * @return the use name or {@code null} if no use name is defined
+   * @return the use name index or {@code null} if no use name index is defined
    */
   @Nullable
-  String getUseName();
+  Integer getUseIndex();
+
+  @Nullable
+  default Integer getEffectiveIndex() {
+    @Nullable Integer useIndex = getUseIndex();
+    return useIndex == null ? getIndex() : useIndex;
+  }
 }
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlAssemblyInstance.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlAssemblyInstance.java
index 4cf6647bb..8ecb88ae3 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlAssemblyInstance.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlAssemblyInstance.java
@@ -115,7 +115,19 @@ public String getName() {
 
   @Override
   public String getUseName() {
-    return getXmlAssembly().isSetUseName() ? getXmlAssembly().getUseName() : null;
+    return getXmlAssembly().isSetUseName() ? getXmlAssembly().getUseName().getStringValue() : null;
+  }
+
+  @Override
+  public Integer getUseIndex() {
+    Integer retval = null;
+    if (getXmlAssembly().isSetUseName()) {
+      AssemblyReferenceType.UseName useName = getXmlAssembly().getUseName();
+      if (useName.isSetIndex()) {
+        retval = useName.getIndex().intValue();
+      }
+    }
+    return retval;
   }
 
   @Override
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlFieldInstance.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlFieldInstance.java
index 328bdc4a6..1acdb1e67 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlFieldInstance.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlFieldInstance.java
@@ -125,7 +125,19 @@ public String getName() {
 
   @Override
   public String getUseName() {
-    return getXmlField().isSetUseName() ? getXmlField().getUseName() : null;
+    return getXmlField().isSetUseName() ? getXmlField().getUseName().getStringValue() : null;
+  }
+
+  @Override
+  public Integer getUseIndex() {
+    Integer retval = null;
+    if (getXmlField().isSetUseName()) {
+      FieldReferenceType.UseName useName = getXmlField().getUseName();
+      if (useName.isSetIndex()) {
+        retval = useName.getIndex().intValue();
+      }
+    }
+    return retval;
   }
 
   @Override
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlFlagInstance.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlFlagInstance.java
index 1cbca0e37..c3047f68b 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlFlagInstance.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlFlagInstance.java
@@ -113,7 +113,19 @@ public boolean isRequired() {
 
   @Override
   public String getUseName() {
-    return getXmlFlag().isSetUseName() ? getXmlFlag().getUseName() : null;
+    return getXmlFlag().isSetUseName() ? getXmlFlag().getUseName().getStringValue() : null;
+  }
+
+  @Override
+  public Integer getUseIndex() {
+    Integer retval = null;
+    if (getXmlFlag().isSetUseName()) {
+      FlagReferenceType.UseName useName = getXmlFlag().getUseName();
+      if (useName.isSetIndex()) {
+        retval = useName.getIndex().intValue();
+      }
+    }
+    return retval;
   }
 
   @Override
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalAssemblyDefinition.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalAssemblyDefinition.java
index c2a1ccee1..25c63964c 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalAssemblyDefinition.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalAssemblyDefinition.java
@@ -130,9 +130,26 @@ public String getName() {
     return ObjectUtils.requireNonNull(getXmlAssembly().getName());
   }
 
+  @Override
+  public Integer getIndex() {
+    return getXmlAssembly().isSetIndex() ? getXmlAssembly().getIndex().intValue() : null;
+  }
+
   @Override
   public String getUseName() {
-    return getXmlAssembly().isSetUseName() ? getXmlAssembly().getUseName() : null;
+    return getXmlAssembly().isSetUseName() ? getXmlAssembly().getUseName().getStringValue() : null;
+  }
+
+  @Override
+  public Integer getUseIndex() {
+    Integer retval = null;
+    if (getXmlAssembly().isSetUseName()) {
+      GlobalAssemblyDefinitionType.UseName useName = getXmlAssembly().getUseName();
+      if (useName.isSetIndex()) {
+        retval = useName.getIndex().intValue();
+      }
+    }
+    return retval;
   }
 
   @Override
@@ -159,7 +176,19 @@ public boolean isRoot() {
 
   @Override
   public String getRootName() {
-    return getXmlAssembly().isSetRootName() ? getXmlAssembly().getRootName() : null;
+    return getXmlAssembly().isSetRootName() ? getXmlAssembly().getRootName().getStringValue() : null;
+  }
+
+  @Override
+  public Integer getRootIndex() {
+    Integer retval = null;
+    if (getXmlAssembly().isSetRootName()) {
+      GlobalAssemblyDefinitionType.RootName rootName = getXmlAssembly().getRootName();
+      if (rootName.isSetIndex()) {
+        retval = rootName.getIndex().intValue();
+      }
+    }
+    return retval;
   }
 
   @SuppressWarnings("null")
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalFieldDefinition.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalFieldDefinition.java
index b094b1614..59289d94d 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalFieldDefinition.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalFieldDefinition.java
@@ -140,9 +140,26 @@ public String getName() {
     return getXmlField().getName();
   }
 
+  @Override
+  public Integer getIndex() {
+    return getXmlField().isSetIndex() ? getXmlField().getIndex().intValue() : null;
+  }
+
   @Override
   public String getUseName() {
-    return getXmlField().isSetUseName() ? getXmlField().getUseName() : null;
+    return getXmlField().isSetUseName() ? getXmlField().getUseName().getStringValue() : null;
+  }
+
+  @Override
+  public Integer getUseIndex() {
+    Integer retval = null;
+    if (getXmlField().isSetUseName()) {
+      GlobalFieldDefinitionType.UseName useName = getXmlField().getUseName();
+      if (useName.isSetIndex()) {
+        retval = useName.getIndex().intValue();
+      }
+    }
+    return retval;
   }
 
   @Override
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalFlagDefinition.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalFlagDefinition.java
index be64d337d..cb82d8b00 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalFlagDefinition.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlGlobalFlagDefinition.java
@@ -140,11 +140,24 @@ public String getName() {
     return getXmlFlag().getName();
   }
 
+  @Override
+  public Integer getIndex() {
+    return getXmlFlag().isSetIndex() ? getXmlFlag().getIndex().intValue() : null;
+  }
+
   @Override
   public String getUseName() {
-    String retval = getXmlFlag().getUseName();
-    if (retval == null) {
-      retval = getName();
+    return getXmlFlag().isSetUseName() ? getXmlFlag().getUseName().getStringValue() : null;
+  }
+
+  @Override
+  public Integer getUseIndex() {
+    Integer retval = null;
+    if (getXmlFlag().isSetUseName()) {
+      GlobalFlagDefinitionType.UseName useName = getXmlFlag().getUseName();
+      if (useName.isSetIndex()) {
+        retval = useName.getIndex().intValue();
+      }
     }
     return retval;
   }
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineAssemblyDefinition.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineAssemblyDefinition.java
index 39b3f7f36..648847cfb 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineAssemblyDefinition.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineAssemblyDefinition.java
@@ -129,6 +129,11 @@ public String getName() {
     return getXmlAssembly().getName();
   }
 
+  @Override
+  public Integer getIndex() {
+    return getXmlAssembly().isSetIndex() ? getXmlAssembly().getIndex().intValue() : null;
+  }
+
   @Override
   public String getGroupAsName() {
     return getXmlAssembly().isSetGroupAs() ? getXmlAssembly().getGroupAs().getName() : null;
@@ -170,6 +175,12 @@ public String getUseName() {
     return null;
   }
 
+  @Override
+  public Integer getUseIndex() {
+    // an inline definition doesn't have a use name index
+    return null;
+  }
+
   @Override
   public Object getValue(@NonNull Object parentValue) {
     // there is no value
@@ -250,12 +261,23 @@ public String getName() {
       return XmlInlineAssemblyDefinition.this.getName();
     }
 
+    @Override
+    public Integer getIndex() {
+      return XmlInlineAssemblyDefinition.this.getIndex();
+    }
+
     @Override
     public String getUseName() {
       // always use the name instead
       return null;
     }
 
+    @Override
+    public Integer getUseIndex() {
+      // always use the name index instead
+      return null;
+    }
+
     @Override
     public boolean isRoot() {
       // a local assembly is never a root
@@ -268,6 +290,12 @@ public String getRootName() {
       return null;
     }
 
+    @Override
+    public Integer getRootIndex() {
+      // a local assembly is never a root
+      return null;
+    }
+
     @SuppressWarnings("null")
     @Override
     public XmlFlagContainerSupport getFlagContainer() {
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineFieldDefinition.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineFieldDefinition.java
index 85b330b0e..092982c61 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineFieldDefinition.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineFieldDefinition.java
@@ -147,6 +147,11 @@ public String getName() {
     return getXmlField().getName();
   }
 
+  @Override
+  public Integer getIndex() {
+    return getXmlField().isSetIndex() ? getXmlField().getIndex().intValue() : null;
+  }
+
   @Override
   public String getGroupAsName() {
     return getXmlField().isSetGroupAs() ? getXmlField().getGroupAs().getName() : null;
@@ -188,6 +193,12 @@ public String getUseName() {
     return null;
   }
 
+  @Override
+  public Integer getUseIndex() {
+    // an inline definition doesn't have a use name index
+    return null;
+  }
+
   @Override
   public Object getValue(@NonNull Object parentValue) {
     // there is no value
@@ -318,12 +329,23 @@ public String getName() {
       return XmlInlineFieldDefinition.this.getName();
     }
 
+    @Override
+    public Integer getIndex() {
+      return XmlInlineFieldDefinition.this.getIndex();
+    }
+
     @Override
     public String getUseName() {
       // always use the name instead
       return null;
     }
 
+    @Override
+    public Integer getUseIndex() {
+      // always use the name index instead
+      return null;
+    }
+
     @SuppressWarnings("null")
     @Override
     public XmlFlagContainerSupport getFlagContainer() {
diff --git a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineFlagDefinition.java b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineFlagDefinition.java
index d3b03a06a..28279ecd1 100644
--- a/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineFlagDefinition.java
+++ b/core/src/main/java/gov/nist/secauto/metaschema/core/model/xml/XmlInlineFlagDefinition.java
@@ -135,6 +135,11 @@ public String getName() {
     return getXmlFlag().getName();
   }
 
+  @Override
+  public Integer getIndex() {
+    return getXmlFlag().isSetIndex() ? getXmlFlag().getIndex().intValue() : null;
+  }
+
   @Override
   public boolean isRequired() {
     return getXmlFlag().isSetRequired() ? getXmlFlag().getRequired() : MetaschemaModelConstants.DEFAULT_FLAG_REQUIRED;
@@ -156,6 +161,12 @@ public String getUseName() {
     return null;
   }
 
+  @Override
+  public Integer getUseIndex() {
+    // an inline definition doesn't have a use name index
+    return null;
+  }
+
   @Override
   public Object getValue(@NonNull Object parentValue) {
     // there is no value
@@ -214,12 +225,23 @@ public String getName() {
       return XmlInlineFlagDefinition.this.getName();
     }
 
+    @Override
+    public Integer getIndex() {
+      return XmlInlineFlagDefinition.this.getIndex();
+    }
+
     @Override
     public String getUseName() {
       // always use the name
       return null;
     }
 
+    @Override
+    public Integer getUseIndex() {
+      // always use the name index instead
+      return null;
+    }
+
     @Override
     public ModuleScopeEnum getModuleScope() {
       return ModuleScopeEnum.LOCAL;
diff --git a/core/src/test/java/gov/nist/secauto/metaschema/core/model/xml/ModuleLoaderTest.java b/core/src/test/java/gov/nist/secauto/metaschema/core/model/xml/ModuleLoaderTest.java
index 9bbc83340..2d6992042 100644
--- a/core/src/test/java/gov/nist/secauto/metaschema/core/model/xml/ModuleLoaderTest.java
+++ b/core/src/test/java/gov/nist/secauto/metaschema/core/model/xml/ModuleLoaderTest.java
@@ -72,7 +72,7 @@ void testUrl() throws MetaschemaException, IOException { // NOPMD - intentional
   void testFile() throws MetaschemaException, IOException {
     ModuleLoader loader = new ModuleLoader();
     URI moduleUri = ObjectUtils.notNull(
-        Paths.get("metaschema/test-suite/docs-models/models_metaschema.xml").toUri());
+        Paths.get("src/test/resources/content/custom-entity-metaschema.xml").toUri());
     IModule module = loader.load(moduleUri);
     assertFalse(module.getExportedRootAssemblyDefinitions().isEmpty(), "no roots found");
   }
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/AbstractClassBinding.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/AbstractClassBinding.java
index bf38fa733..adbf10467 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/AbstractClassBinding.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/AbstractClassBinding.java
@@ -88,6 +88,12 @@ public String getUseName() { // NOPMD
     return null;
   }
 
+  @Override
+  public Integer getUseIndex() {
+    // a use name index is never provided
+    return null;
+  }
+
   @SuppressWarnings("null")
   @Override
   public String toCoordinates() {
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/AbstractFieldProperty.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/AbstractFieldProperty.java
index bfe0ec613..83026cccc 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/AbstractFieldProperty.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/AbstractFieldProperty.java
@@ -89,6 +89,12 @@ public String getUseName() {
     return ModelUtil.resolveToString(getFieldAnnotation().useName());
   }
 
+  @Override
+  public Integer getUseIndex() {
+    int value = getFieldAnnotation().useIndex();
+    return value == Integer.MIN_VALUE ? null : value;
+  }
+
   @Override
   public boolean isInXmlWrapped() {
     return getFieldAnnotation().inXmlWrapped();
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/ClassBindingAssemblyProperty.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/ClassBindingAssemblyProperty.java
index 3dbdfd5d3..28be18fe9 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/ClassBindingAssemblyProperty.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/ClassBindingAssemblyProperty.java
@@ -101,6 +101,12 @@ public String getUseName() {
     return ModelUtil.resolveToString(getAssemblyAnnotation().useName());
   }
 
+  @Override
+  public Integer getUseIndex() {
+    int value = getAssemblyAnnotation().useIndex();
+    return value == Integer.MIN_VALUE ? null : value;
+  }
+
   @Override
   public String getXmlNamespace() {
     return ObjectUtils
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultAssemblyClassBinding.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultAssemblyClassBinding.java
index 37d4ba44a..5329046a4 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultAssemblyClassBinding.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultAssemblyClassBinding.java
@@ -30,8 +30,8 @@
 import gov.nist.secauto.metaschema.core.datatype.markup.MarkupMultiline;
 import gov.nist.secauto.metaschema.core.model.IChoiceInstance;
 import gov.nist.secauto.metaschema.core.model.IFlagContainerSupport;
-import gov.nist.secauto.metaschema.core.model.IModule;
 import gov.nist.secauto.metaschema.core.model.IModelContainerSupport;
+import gov.nist.secauto.metaschema.core.model.IModule;
 import gov.nist.secauto.metaschema.core.model.constraint.IConstraint.InternalModelSource;
 import gov.nist.secauto.metaschema.core.model.constraint.IModelConstrained;
 import gov.nist.secauto.metaschema.core.util.ObjectUtils;
@@ -162,6 +162,12 @@ public String getName() {
     return getMetaschemaAssemblyAnnotation().name();
   }
 
+  @Override
+  public Integer getIndex() {
+    int value = getMetaschemaAssemblyAnnotation().index();
+    return value == Integer.MIN_VALUE ? null : value;
+  }
+
   @Override
   public boolean isInline() {
     return false;
@@ -186,6 +192,12 @@ public String getRootName() {
     return qname == null ? null : qname.getLocalPart();
   }
 
+  @Override
+  public Integer getRootIndex() {
+    int value = getMetaschemaAssemblyAnnotation().rootIndex();
+    return value == Integer.MIN_VALUE ? null : value;
+  }
+
   @Override
   public QName getRootXmlQName() {
     // Overriding this is more efficient, since it is already built
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFieldClassBinding.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFieldClassBinding.java
index 1b4f72989..0cfa3e517 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFieldClassBinding.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFieldClassBinding.java
@@ -141,6 +141,12 @@ public String getName() {
     return getMetaschemaFieldAnnotation().name();
   }
 
+  @Override
+  public Integer getIndex() {
+    int value = getMetaschemaFieldAnnotation().index();
+    return value == Integer.MIN_VALUE ? null : value;
+  }
+
   @Override
   public Object getDefaultValue() {
     return getFieldValueInstance().getDefaultValue();
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFieldValueProperty.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFieldValueProperty.java
index 838f7ac03..8a83e5b7c 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFieldValueProperty.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFieldValueProperty.java
@@ -133,6 +133,12 @@ public String getUseName() {
     return null;
   }
 
+  @Override
+  public Integer getUseIndex() {
+    // TODO: implement?
+    return null;
+  }
+
   @Override
   public @NonNull ModelType getModelType() {
     // TODO: is this right? Is there a way to not make this derived from a property?
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFlagProperty.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFlagProperty.java
index 2f5c0f62f..0dceae00a 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFlagProperty.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/DefaultFlagProperty.java
@@ -149,6 +149,12 @@ public String getUseName() {
     return ModelUtil.resolveToString(getFlagAnnotation().useName());
   }
 
+  @Override
+  public Integer getUseIndex() {
+    int value = getFlagAnnotation().useIndex();
+    return value == Integer.MIN_VALUE ? null : value;
+  }
+
   @Override
   public String getXmlNamespace() {
     return ModelUtil.resolveOptionalNamespace(getFlagAnnotation().namespace(), getParentClassBinding());
@@ -235,12 +241,23 @@ public String getName() {
       return getJavaFieldName();
     }
 
+    @Override
+    public Integer getIndex() {
+      return DefaultFlagProperty.this.getIndex();
+    }
+
     @Override
     public String getUseName() {
       // always use the name instead
       return null;
     }
 
+    @Override
+    public Integer getUseIndex() {
+      // always use the index instead
+      return null;
+    }
+
     @Override
     public MarkupMultiline getRemarks() {
       return DefaultFlagProperty.this.getRemarks();
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/SimpleFieldProperty.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/SimpleFieldProperty.java
index eff333ce2..09a9d6a94 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/SimpleFieldProperty.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/SimpleFieldProperty.java
@@ -112,20 +112,10 @@ protected IDataTypeHandler newDataTypeHandler() {
     return IDataTypeHandler.newDataTypeHandler(this);
   }
 
-  @Override
-  public boolean isInXmlWrapped() {
-    return getFieldAnnotation().inXmlWrapped();
-  }
-
   protected Object getDefaultValue() {
     return defaultValue;
   }
 
-  @Override
-  public String getUseName() {
-    return ModelUtil.resolveToString(getFieldAnnotation().useName());
-  }
-
   @Override
   public Object defaultValue() {
     return getMaxOccurs() == 1 ? getDefaultValue() : getPropertyInfo().newPropertyCollector().getValue();
@@ -187,6 +177,16 @@ public String getName() {
       return getJavaFieldName();
     }
 
+    @Override
+    public Integer getIndex() {
+      return null; // no index by default;
+    }
+
+    @Override
+    public Integer getUseIndex() {
+      return null; // none
+    }
+
     @Override
     public String getUseName() {
       return ModelUtil.resolveToString(getFieldAnnotation().useName());
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundAssembly.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundAssembly.java
index 682b87fa3..766b6ce04 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundAssembly.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundAssembly.java
@@ -86,6 +86,15 @@
   @NonNull
   String useName() default Constants.NO_STRING_VALUE;
 
+  /**
+   * The binary use name of the assembly.
+   * <p>
+   * The value {@link Integer#MIN_VALUE} indicates that there is no use name.
+   *
+   * @return the index value
+   */
+  int useIndex() default Integer.MIN_VALUE;
+
   /**
    * The namespace to use for associated XML elements.
    * <p>
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundField.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundField.java
index d6bedffcd..fc562c69b 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundField.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundField.java
@@ -95,6 +95,15 @@
   @NonNull
   String useName() default Constants.NO_STRING_VALUE;
 
+  /**
+   * The binary use name of the field.
+   * <p>
+   * The value {@link Integer#MIN_VALUE} indicates that there is no use name.
+   *
+   * @return the index value
+   */
+  int useIndex() default Integer.MIN_VALUE;
+
   /**
    * The namespace to use for associated XML elements.
    * <p>
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundFlag.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundFlag.java
index 4a66814f6..f5113ed2e 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundFlag.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/BoundFlag.java
@@ -80,6 +80,15 @@
   @NonNull
   String useName() default Constants.NO_STRING_VALUE;
 
+  /**
+   * The binary use name of the flag.
+   * <p>
+   * The value {@link Integer#MIN_VALUE} indicates that there is no use name.
+   *
+   * @return the index value
+   */
+  int useIndex() default Integer.MIN_VALUE;
+
   /**
    * XML target namespace of the XML Schema element.
    * <p>
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/MetaschemaAssembly.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/MetaschemaAssembly.java
index 109ae45cc..e97e1cedc 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/MetaschemaAssembly.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/MetaschemaAssembly.java
@@ -82,6 +82,15 @@
   @NonNull
   String name();
 
+  /**
+   * The binary name of the assembly.
+   * <p>
+   * The value {@link Integer#MIN_VALUE} indicates that there is no index.
+   *
+   * @return the index value
+   */
+  int index() default Integer.MIN_VALUE;
+
   /**
    * Name of the root XML element or the JSON/YAML property.
    * <p>
@@ -92,6 +101,15 @@
   @NonNull
   String rootName() default Constants.NO_STRING_VALUE;
 
+  /**
+   * The binary root name of the assembly.
+   * <p>
+   * The value {@link Integer#MIN_VALUE} indicates that there is no root index.
+   *
+   * @return the index value
+   */
+  int rootIndex() default Integer.MIN_VALUE;
+
   /**
    * XML target namespace of the XML element.
    * <p>
diff --git a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/MetaschemaField.java b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/MetaschemaField.java
index 30c1506ab..7a7bd94f6 100644
--- a/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/MetaschemaField.java
+++ b/databind/src/main/java/gov/nist/secauto/metaschema/databind/model/annotations/MetaschemaField.java
@@ -78,9 +78,27 @@
   @NonNull
   String name();
 
+  /**
+   * The binary name of the assembly.
+   * <p>
+   * The value {@link Integer#MIN_VALUE} indicates that there is no index.
+   *
+   * @return the index value
+   */
+  int index() default Integer.MIN_VALUE;
+
   @NonNull
   String useName() default Constants.NO_STRING_VALUE;
 
+  /**
+   * The binary use name of the assembly.
+   * <p>
+   * The value {@link Integer#MIN_VALUE} indicates that there is no use name.
+   *
+   * @return the index value
+   */
+  int useIndex() default Integer.MIN_VALUE;
+
   /**
    * Get the metaschema class that "owns" this assembly, which is the concrete
    * implementation of the metaschema containing the assembly.