In previous sections, we have deliberately omitted a lot of DocBook's history. XML has an older brother, Standard Generalized Markup Language (SGML).
Until mid-2002, no discussion of DocBook would have been complete without a long excursion into SGML, the differences between SGML and XML, and detailed descriptions of the SGML DocBook toolchain. Life can be simpler now; an XML DocBook toolchain is available in open source, works as well as the SGML toolchain ever did, and is easier to use.
