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).
As of September 19, 2006 , CCEL had 650 documents in this format.  The advantage of using an XML-based format is that it can be converted to HTML by using an XSLT stylesheet. Also, standard XML tools can convert to PDFand RTF .
The last Document Type Definition of the format As of November 8, 2012 – version 1.04  – was released on January 20, 2003. 
- The SWORD Project – Bible study software project MOST That supports operating systems , Numerous PDA handhelds, and web services.
- Go Bible app for Java mobile phones.
- Open Scripture Information Standard .
- Zefania XML Bible Markup Language.
- Jump up^ Plantinga 2003, Introduction, ¶7: ‘… the first version of ThML was designed in the summer of 1998 …’
- Jump up^ Plantinga 2003, Introduction, ¶4: ‘Commercial formats, including STEP and theLogos Library System(LLS), are not designed for integration with the Internet, and preparing for these systems requires expensive software, beyond the means of most Individuals. Publication in one of these formats may also be controlled by the company or consortium in question. As a result, few public-domain or on-line texts are available in these formats.
- Jump up^ “The Vision” . CCEL . Christian Classics Ethereal Library. 2006-09-19. Retrieved 2007-01-06 .
There are 650 XML documents
- Jump up^ Theological Markup Language (ThML) , CCEL,
ThML Definition [v. 1.04].
- Jump up^ Plantinga 2003, Header: ‘Version 1.04, January 20, 2003’