XSL-FO
XSL-FO (XSL Formatting Objects) is an XML-based markup language used for specifying the formatting and layout of XML documents for print or PDF output. It defines a set of formatting objects and properties that describe how content should be presented, such as page layouts, fonts, and spacing. It is typically used in conjunction with XSLT to transform XML data into formatted documents.
Developers should learn XSL-FO when they need to generate high-quality, structured print documents or PDFs from XML data, such as reports, invoices, or books. It is particularly useful in enterprise environments where XML is the primary data format and precise control over pagination, typography, and layout is required. Use cases include batch document generation in publishing, legal, or financial systems.