Docbook 5.1 adds support for topic-based authoring. It’s studiedly neutral in its approach to topic-based authoring, in contrast with DITA’s almost religious zeal for the historical inevitability of the Topicalypse.
Without naming any names, the Docbook Definitive Guide V1.3 states:
One modern school of thought on technical documentation stresses the development of independent units of documentation, often called topics, rather than a single narrative.
It’s clear from this that the Docbook Technical Committee did not arrive at the topic epiphany by contemplating their navel in isolation, or by a blinding flash of light on the road to Damascus. And while no names are mentioned in this introduction to a pragmatic concession to topic-based authoring, Docbook 5.1 incorporates most, if not all of DITA’s features, while maintaining Docbook’s core strength of static linear narrative targeting a book-like output medium.
One thing that really screams: “Come to the mountain!” is the ability to build Docbook 5.1 topic-based output incorporating DITA topics. Just-in-time xsl processing (<transform>) is used to incorporate existing DITA topics in Docbook 5.1 topic assemblies, allowing you to come back to the fold without an expensive conversion of existing content.
Docbook 5.1 lacks the topic-based purity of DITA, implementing a dual (but isolated) static linear narrative / modular topic model, in contrast to DITA’s focus on topics uber alles, and adopting a pragmatic, descriptive approach (“hey, looks like people want to do this“), rather than a religious, prescriptive approach (“this is the one true way!“).
However, it looks to have learned from DITA, including DITA’s shortcomings, and brings its rich semantic model to the table, as well as its installed base of expertise and tooling.
A pragmatic approach is the approach that organisations need to take when moving from a pure static linear narrative approach to a modular topic-based one, so Docbook’s pragmatic compromise, along with its tooling maturity, may sit well with many organisations moving in that direction.