XFA

Key takeaways

XFA belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect XFA to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of XFA from memory before moving on to harder problems.

Reference excerpt

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 the PDF 1.5 specification. The XFA specification is referenced as an external specification necessary for full application of the ISO 32000-1 specification (PDF 1.7). The XML Forms Architecture was not standardized as an ISO standard, and has been deprecated in PDF 2.0.

Overview XFA's main extension to XML are computationally active tags. In addition, all instances created from a given XFA form template keep the specification of data capture, rendering, and manipulation rules from the original. Another major advantage of XFA is that its data format allows compatibility with other systems, and with changes to other technology, applications and technology standards. According to JetForm's submission to the World Wide Web Consortium, "XFA addresses the needs of organizations to securely capture, present, move, process, output and print information associated with electronic forms." The XFA proposal was submitted to the W3C in May 1999. In 2002, the JetForm Corporation was acquired by Adobe Systems, and the latter introduced XFA forms with PDF 1.5 and the subsequent Acrobat releases (6 and 7) in 2003. XFA forms are saved internally in PDF files or as XDP (XML Data Package) files which can be opened in Adobe's LiveCycle Designer software. An XDP can package a PDF file, along with XML form and template data. XDP provides a mechanism for packaging form components within a surrounding XML container. Although XFA can make use of PDF, XFA is not tied to a particular page description language. The XFA specification includes an appendix that discusses details of the Adobe-specific XFA implementation and behaviors of Adobe products that deviate from the XFA specification. Data filled in an XFA form may be submitted to a host using an HTTP POST operation in XDP format, PDF format, XFDF format, XML 1.0 format or as an URL-encoded format. XFA supports the use of XSLT to transform the XML data before it is loaded to XFA Data DOM or after it is unloaded from XFA Data DOM. One of XFA approaches to pagination duplicates the pagination logic and much of the syntax of XSL-FO. XFA forms are synonymous with SmartForms in the Australian government. XFA forms have also been used extensively by the Government of Canada; Immigration, Refugees and Citizenship Canada distributes many of its application forms as XFA PDFs, which must be downloaded and opened in Adobe Reader rather than a web browser or mobile device.

Static and dynamic forms XFA defines static forms (since XFA 2.0 and before) and dynamic forms (since XFA 2.1 or 2.2). In a static form the form’s appearance and layout is fixed, regardless of the field content. Any unfilled fields are present in the form. By default, static forms do not require re-rendering. XFA recognises two types of static forms: "old-style static forms" (using "full XFA") and XFAF (a subset of full XFA, defined since XFA 2.5). Dynamic forms (defined since XFA 2.1 or 2.2) can change in appearance in several ways in response to changes in the data. Dynamic form requires rendering of its content on file opening. Dynamic forms may also be designed to change structure to accommodate changes in the structure of the data supplied to the form. For example, a page of a form may be omitted if there is no data for it. Another example is a field that may occupy a variable amount of space on the page, resizing itself to efficiently hold its content. Dynamic form cannot rely on a PDF representation of its boilerplate, because the positioning and layout of the boilerplate change as the fields grow and shrink or as subforms are omitted and included.

Usage with Portable Document Format PDF 1.7 supports two different methods for integrating data and PDF forms.

AcroForms (also known as Acrobat forms), introduced and included in the PDF 1.2 format specification. Adobe XML Forms Architecture (XFA) forms, introduced in the PDF 1.5 format specification as an optional feature (The XFA specification is not included in the PDF specification, it is only referenced.) Adobe XFA Forms are not compatible with AcroForms. When an XFA is packaged inside a PDF file, it is placed in the AcroForm document resources dictionary ("Shell PDF") or referenced from the AcroForm entry in the document catalog. Creating XFA Forms for use in Adobe Reader requires Adobe LiveCycle Designer. Adobe Reader contains "disabled features" for use of XFA Forms, that will activate only when opening a PDF document that was created using enabling technology available only from Adobe. The XFA Forms are not compatible with Adobe Reader prior to version 6.

Profiles Starting with XFA 2.5 forms can use a subset of the full XFA capability. Currently the only specified is the XFAF profile. XFA can be used as:

full XFA - which express all of the form, including boilerplate, directly in XFA (without any PDF or without a complete PDF background). It can be packaged inside a "shell PDF" with minimal PDF markup or as a standalone XDP. It is used for dynamic XFA forms (since XFA 2.1) and also for so called "traditional" (old-style) static XFA forms. Optionally it may include a pre-rendered depiction of the XFA form as PDF pages - but it is useful only for traditional static forms. Dynamic XFA must be rendered on file opening. XFAF (XFA Foreground) subset - (introduced in XFA 2.5) - a form in which each page of the XFA form overlays a PDF background. It can be used only for static XFA forms. This architecture uses only a subset of XFA. It can be packaged inside a regular PDF document or as a standalone XDP file with embedded PDF. In XFAF each XFA field corresponds to a PDF interactive field (AcroForm field).

Packaging XFA forms can be created and used as PDF 1.5 - 1.7 files or as XDP (XML Data Package). The format of an XFA resource in PDF is described by the XML Data Package Specification. PDF may contain XFA in XDP format, but XFA may also contain PDF. When the XFA (XML Forms Architecture) grammars used for an XFA form are moved from one application to another, they must be packaged as an XML Data Package. The XDP may be a standalone document or it may in turn be carried inside a PDF document. XFA Form packaging variants (using XDP):

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Worked examples

Example 1 — a first encounter with XFA

Start with the simplest possible case. Write down what XFA claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to XFA before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about XFA ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of XFA

In research: XFA appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses XFA in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: XFA is common in secondary-school and first-year university syllabi. It links to neighbouring topics Markup languages, XML-based standards, so understanding it makes those chapters shorter.
In everyday life: Look for XFA outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study XFA in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what XFA means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain XFA out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is XFA in simple terms?

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 the PDF 1.5 specification.

Why does XFA matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study XFA?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on XFA.