### Add Variable Structure dialog

Use this dialog to define a variable and add it to the tree of variable structures in the Variable Structures page of the Expression Editors.

You create variable structures in this dialog to define the structure of a variable for design purposes. For example, it is easier to browse the XPath variable in the structure view rather than viewing the XML schema of the XPath variable. Variable structures do not create variables. Variables are created at runtime as the target of the assign action in the stage.

You can declare your own variable structures based on:

- XML types, including

- Schema elements
- WSDL elements
- Schema types
- WSDL types

- MFLs
- Service interfaces
- Simple types (string or any XML)

You can use this feature directly for all user-defined variables, as well as `$inbound`, `$outbound`, and `$fault`. However, you cannot use it directly to access XML attachments in `$attachments`, headers in `$header`, or documents and RPC parameters in `$body`, with one exception- you can use it directly to access documents and parameters in `$body` for request messages received by a WSDL proxy service.

When you create a variable structure based on XML types, MFLs, or service interfaces, you must enter the following information into the fields at the top of the page:

Option | Description
--- | ---
Structure Label | A display name for the variable you want to create. This display name enables you to give a meaningful name to the structure so you can recognize it at design time but it has no impact at run time.
Structure Path | The path of the variable structure at run time

For more information about working with variable structures, see Working with Variable Structures in the AquaLogic Service Bus User Guide