Moreover, the creation of these SGML elements could facilitate the production of large print and voice-synthesized versions of the text as well. The DTD defines the valid markup elements for a document type and what they mean. In other words, a DTD is a descriptive envelope for the content of the document. The preceding DTD defines a document type article as consisting of two structural parts, author and text . Finally, the text element has an attribute style .
Attributes modify the elements by carrying additional information about the document section.
No physical manifestation is presumed by the style attribute value. The SGML parser determines whether the document structure is valid. Only one set of markup should be used. If a second markup is required for nonvisual encoding, it will likely not happen. Archival documents must always contain the richest possible markup, thereby further facilitating access to the document.