High Quality Content by WIKIPEDIA articles! The Theological Markup Language (ThML) is a "royalty-free" XML-based format created in 1998 by the Christian Classics Ethereal Library (CCEL) to create electronic theological texts. Other formats such as STEP and Logos Library System (LLS) were found unacceptable by CCEL as they are proprietary, prompting the creation of the new language. The ThML format borrowed elements from a somewhat similar format, the Text Encoding Initiative (TEI).