### Variable Structures page

This page appears in the XQuery/XSLT Expression Editor, the XPath Expression Editor, and the Condition Editor.

The Variable Structures page displays variables and their contents as trees. It includes the built-in message context variables `attachments`, `body`, `header`, `outbound`, and `inbound`, as well as any user-defined variables. It includes `fault` if the context of the expression is appropriate (htat is, in an error handler). The `outbound` variable is always listed; even though it is not valid in every context. If `outbound` is used in invalid contexts, it will be reported when validating.

Each variable structure mapping entry has a label and maps a variable or variable path to one or more structures. The scope of these mappings is a stage or a route node.

You can drag items from this page to the editor's Expression page to insert them into the current expression. They are inserted as XPath expressions.

To define a new variable and add it to the variable structure tree, click Add to open the Add Variable Structure dialog.

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