Succession in standardization: grafting XML onto SGML

Succession in standardization is often a problem. The advantages of improvements must be weighed against those of compatibility. If compatibility considerations dominate, a grafting process takes place. According to our taxonomy of succession, there are three types of outcomes. A Type I succession, where grafting is successful, entails compatibility between successors, technical paradigm compliance and continuity in the standards trajectory. In this paper, we examine issues of succession and focus on the Extensible Markup Language (XML). It was to be grafted on the Standard Generalized Markup Language (SGML), a stable standard since 1988. However, XML was a profile, a subset and an extension of SGML (1988). Adaptation of SGML was needed (SGML 1999) to forge full (downward) compatibility with XML (1998). We describe the grafting efforts and analyze their outcomes. Our conclusion is that although SGML was a technical exemplar for XML developers, full compatibility was not achieved. The widespread use of HyperText Markup Language (HTML) exemplified the desirability of simplicity in XML standardization. This and HTML's user market largely explain the discontinuity in SGML-XML succession.