The production of technical documentation is undergoing something of a revolution at present. This is due to the maturing of a raft of technologies based on the XML markup language. Broadly speaking, these technologies provide a solution that sits between monolithic documents-as-files, such as Word documents, and relational databases, which aggregate fine-grained information records into tables.

With a Word document, the unit of content is the same as the unit of presentation: a file is edited, and the same file is printed. This applies equally to web pages (HTML), but with the page as the unit. In practice, it is difficult and time-consuming to identify, extract and recombine fragments of documents to produce new deliverables.

With a relational database, the information records can be conjoined, aggregated and filtered in very complex ways, using the SQL query language. However, databases are not really suited to holding large free-text elements, like a section of a document. Also, there is no notion of hierarchical structuring in query
output, in contrast to the hierarchy of chapters, sections, sub-sections and phrases that we are familiar with in documents.

The XML-based solutions aim to provide a middle course. Content is created and held in a form that is structured enough to identify, extract and recombine fragments of documents to produce new deliverables. At the same time, the content does not carry information about presentation (either the target format, or the details of layout). This is provided by transformations of the content to produce deliverables in different formats, such as PDF for printable documents, or hypertext (XHTML-based) for web presentation or online Help.

A set of XML documents can be treated as a database of elements and attributes, but structured hierarchically within documents, rather than into flat tables. The XQuery language allows query access, full-text search and updating, in a manner comparable to SQL.

One particular XML-based solution is DITA:

“The Darwin Information Typing Architecture (DITA) builds content reuse into the authoring process. DITA defines an XML architecture for designing, writing, managing, and publishing many kinds of information in print and on the Web.
The standard is advanced through an open process by the OASIS DITA Technical Committee, a group that encourages new participation from developers and users”.

The Wikipedia article is a good place to start for further information.

I think that DITA is the best opportunity yet to modernise the way we produce and maintain technical documentation: requirements documents, specifications, manuals, user documentation, online Help, and so on. By designing and constructing a content base of discrete topics, we can reuse content, define deliverables in flexible ways, and produce these for different target formats.