HTML is a relatively simple application with a restricted tag set, designed specifically for Web distribution and access. In general, however, SGML-based languages, for example TEI, describe the logical structure and meaning of documents. So, for example, SGML might be used to identify components such as the title, author and section headings of a piece of prose but there might be no indication as to where to display these components on the screen or what fonts to use. Because SGML-based languages, with the exception of HTML, do not generally describe appearance, an application is required to convert the documents in question to a suitable viewing format. This application could be an SGML viewer, for example, Softquad's Panorama for Netscape.
Panorama uses style sheets to relate logical markup to physical appearance.
Alternatively, SGML might be converted to another format for display. They are converted to HTML and both the TEI and HTML versions are made available to the end-user. In other words, they are not proprietary to particular computer programs. Italics can be used for a variety of purposes, and most SGML tagsets can clearly delineate an emphatic word from a book's title or a chapter heading. SGML in Textual Encoding Initiative Research SGML was chosen as the vehicle for the TEI Guidelines, and the main deliverable of the TEI project is an SGML DTD describing over four hundred textual feature definitions, along with associated documentation and examples.