Clark has lived in Bangkok, Thailand since , and is permanent Thai resident. He owns a company called Thai Open Source Software Center, which provides him a legal framework for his open-source activities. Clark is the author and creator of groff, as well as an XML editing mode for GNU Emacs.
Work on XML
Clark served as technical lead of the working group that developed XML - notably contributing the self-closing, empty element tag syntax, and the name XML. His contributions to XML are cited in dozens of books on the subject. Clark is the author or co-author of a number of influential specifications and implementations, including:
DSSSL: An SGML transformation and styling language.
XSLT: XSL Transformations, a part of the XSL family. He was the editor of the XSLT 1.0 specification.
XPath: Path language for addressing XML documents; used by XSLT but also as a free-standing language. He was the editor of the XPath 1.0 specification.
RELAX NG: an XML Schema language, with both an explicit XML syntax and a compact syntax. Clark was critical of the XML Schema (W3C) language (also known as XSD)[7] and developed RELAX NG in response
Clark Notation: A way to express an XML Name in a compact way[9]
Ballerina: Ballerina is an open source general-purpose programming language for application programmers.
Clark is listed as a member of the working group that developed the JavaStream processing API for XML (StAX) JSR 173 at the JCP.[10]
Software Industry Promotion Agency (SIPA)
From until late , Clark worked for Thailand's Software Industry Promotion Agency (SIPA), to promote open source technologies and open standards in the country. This work included pushing the Thai localization of OpenOffice.org office suite and the Mozilla Firefox web browser, along with other open source software packages.
Other projects at SIPA include:
Chantra: An open source Thai project with programs for Windows, like the OpenCD project.
Suriyan GNU/Linux: A user-friendly "instant server" system for small and medium-sized companies[11] not to be confused with SIPA's new, unrelated project with a similar name, Suriyan Linux Live CD.[12]
Web site: Schema Wars: XML Schema vs. RELAX NG. 11 May 2019. webreference.com. 4 March 2019. https://web.archive.org/web/20190304043049/http://webreference.com/xml/column59/index-2.html. dead.