Wikipedia
XFA
XFA (also known as XFA forms) stands for XML Forms Architecture, a family of proprietary XML specifications that was suggested and developed by JetForm to enhance the processing of web forms. It can be also used in PDF files starting with PDF 1.5 specification. XFA specification is referenced as an external specification indispensable for the application of ISO 32000-1 specification (PDF 1.7). XML Forms Architecture was not standardized as an ISO standard.