Xalan
Xalan is an open-source XSLT processor for transforming XML documents into other formats, such as HTML, text, or other XML structures. It implements the XSLT and XPath standards from the W3C, allowing developers to apply stylesheets to XML data. Originally developed by Apache, it is widely used in Java and C++ environments for XML processing tasks.
Developers should learn Xalan when working with XML-based systems that require transformations, such as generating web content from XML data, converting between XML schemas, or integrating legacy systems. It is particularly useful in Java applications where XML processing is common, such as in enterprise web services, document management, or data interchange formats. Xalan provides a reliable, standards-compliant way to handle complex transformations without reinventing the wheel.