# Adding redefine elements

You can use the `redefine` mechanism to redefine simple and complex types, groups, and attribute groups obtained from external schema files. When you redefine a component, you are modifying its contents.

Like the `include` mechanism, `redefine` requires the external components to be in the same target namespace as the redefining schema, although external components from schemas that have no namespace can also be redefined.

The following instructions were written for the Resource perspective, but they will also work in many other perspectives.

To add a redefine element, complete the following steps:

1. Open your XML schema in the XML schema editor.
2. In the Design view, right-click in the Directives section and click Add Redefine.
3. In the Select XML schema file wizard, you can import an XML schema that is located in your workspace or you can import a schema from an HTTP Web address. The XML schema file that you select must have the same namespace as the current schema.
   - If you want to import an XML schema located in your workspace:
     1. Select Workbench projects and click Next.
     2. Select the schema that you want to import and click Finish.
   - If you want to import an XML schema located at an HTTP Web address:
     1. Select HTTP and click Next.
     2. Type the URL of the XML schema and click Finish.
        Note: A local copy of the schema is not stored in your workspace. If you validate your schema, the schema's contents are checked from the URL that you specify.
4. Optional: Use the Properties view to define additional properties for your import element.
   1. If you want to edit the location of the included XML schema file, click the General tab and type the new location display in the Schema location field.
   2. Click the Documentation tab if you want to provide any information about this redefine element. The Documentation page is used for human readable material, such as a description.
   3. Click the Extensions tab if you want to add application information elements to your annotations of schema components. The Extensions page allows you to specify the schema and add XML content to your annotations.

Once you have added the redefine element to your XML schema, you can redefine any of the simple and complex types, groups, and attribute groups in the XML schema you selected in the redefine element.

Related tasks
Adding import elements
Adding include elements
Related reference
XML namespaces