When I started my career, XML was ubiquitous. The meta-information in a Java JAR file - the manifest - follows a proprietary format. But Java EE designers built it from the ground up on XML: meta-information of all artifacts is in XML format e.g. web.xml, ejb-jar.xml, application.xml, etc. Java EE is one example I experienced personally. But XML was everywhere in the enterprise world at the time. Its prevalence manifested itself in two areas: configuration and data transfer.