How-to...
   Create a Return Type
   Add a Complex Child Element to a Return Type
   Check Namespaces in Return Types
   Create Conditional Elements in Return Types
   Add a Where Clause to a Query
   Use the XQuery Expression Editor
   Use the Source Editor

Reference
   XQuery Language Version Support
   Built-in XQuery Functions

Related Topics
How-to...
    Create Your First Data Services
    Test a Read Function and Simple Update
    Test a Create or Delete Procedure
    How To Develop Good XQSEs
Concepts...
   Understanding Data Service Annotations
Reference...
   XQuery Scripting Extensions