Why read the DTD documentation?
Although XML allows for standalone, DTD-less ‘well formed’ documents (more info), the DTD is central to BPG XML content. Features have been introduced to make the DTD easier to decipher and use. For example, self-explanatory full element names are used (titlegroup rather than tig), but it’s always important to understand what’s intended by the markup and this is described in the documentation. Elements can also perform very different functions in different contexts (e.g. title). Furthermore, the definition of content models has in some cases been relaxed to be XML-compliant and so it’s important in these cases to understand that what’s actually required for DTD 4-compliancy might be stricter than the content model appears. For example, see the note to ‘How to read a content model’.
