XML documents provide a tremendous advantage to narrowing search results because of their heirarchical structure and use of multiple document summary fields.
Web Search provides complete hierarchical searching using the fieldname=search_criteria operator. For example, you can find information anywhere in the XML document, within any of the title tags, or limit it to within the title tag that is part of the <DOCUMENT><SUMMARY> hierarchy.
The following table shows example uses of the fieldname=search_criteria operator when performing a search in XML documents.