DTDs are most often used on large document management projects where enforcing coherence is essential. Large documentations (up to thousands of pages) are usually written by several authors over a long period of time. When left on their own, authors tend to use different styles. The resulting documents are a patchwork of individual pieces rather than a synchronous whole. This can severely disable the end users of the documentation.

To combat this problem, organizations typically use a manual of style or guidelines. The guidelines describe how documents should be organized: the formatting that will be used on subsections, how the glossary will be organized, which visual cues will be used to navigate the document, etc.

DTDs are the next logical step in developing a formalized guideline for a large document. There are several advantages to using a DTD. For example: a computer can validate documents automatically and reject those documents that are non-compliant. More importantly, the computer can guide authors through the guidelines, for example, by prompting for an abstract where one is required.