XFDL, Extensible Forms Description Language File (.xfdl)
The XFDL Website file format
XFDL files are, mostly, used for business matters. These XML structured files often contain legally-binding contracts or forms. This file type was developed to ensure the auditability, security, non-repudiation and preservation of sensible business transaction data. The XFDL forms are standardized and can be used by different business for different purposes. Its usage is quite common in eCommerce.
Technical details of XFDL files
The XFDL file contains a number of important information about the business form. The data includes the layout of the form, any details and information concerning transactions as well as a digital signature. Furthermore, mathematical and conditional expressions are stored in the XFDL file. XFDL files are based on UDFL (Universal Forms Description Language) and differ from it in that they adapted the XML format.