Succession in standardization: Grafting XML onto SGML

Succession in standardization is usually a problem. The advantages of improvements are weighed against those of compatibility. If compatibility considerations dominate, a grafting process takes place. This process need not lead to compatibility. According to our taxonomy of successor standards, there are three types of succession (outcomes). Type I, where grafting is achieved, 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 (SGML1999) to forge full (downward) compatibility with XML (1998). We describe the grafting efforts and analyze their outcomes. We conclude that XML largely fits the SGML paradigm. SGML was a technical exemplar for XML developers. In contrast, widespread use of HTML exemplified the desirability of simplicity in XML standardization. The latter issue and HTML's user market largely explain discontinuity in SGML-XML succession.