Yagsbook is an XML format similar to Docbook. Initially is was going to be a few addons to Docbook, but it was soon decided that Docbook was too tied to its own domain (technical documentation) to be useful for a roleplaying game. There are some similarities between Docbook and Yagsbook, but these are for historical reasons.
There are three types of top level documents in Yagsbook and many more support documents which may be included by the top three.
The principle type of document in Yagsbook is the <article> . Articles are designed to be the top level holder of all other document types, and as such is the only document type which contains extensive header information.
Though besteries and character documents are also considered top level, these can be referenced from an article and inlined. No other document type can currently inline an article.
Articles are the basis of the Encyclopedia and are the main elements of Yags rules.
A <bestiary> document contains one or more <beast> elements and nothing else. Basically, it is a collection of animal and monster descriptions, which may be used to generate a standalone document.
The contents of a bestiary may be referenced and included from an article, or it can be used to generate a standalone document. In the latter case, each beast may be rendered as a single full page.
The third type of top level document is the character repository, which may be used to generate either a character sheet for a single character, or a booklet of character descriptions.
Character repositories may contain actual characters, character templates or character packages. All follow a very similar format, differing only on what content is required and how it is presented.
A <character> element is split into a system neutral section (the description) and game specific sections (statistic blocks). A single character can be described using several statistic blocks, one for each system.