Formulas, Tables, Figures
Tables, figures and formulas are most frequently found as floating features within the body of technical and scientific documents. They do however occur in other forms of writing and are therefore discussed here. They are not formatted in the same way as the text of a document with respect to page breaks, text alignment etc. and generally require special coding conventions. Paragraphs are generally written and formatted on a line-by-line basis, but these features are written and frequently formatted as independent blocks of text, requiring special functions of a formatter, for example, alignment of cells in a formula or operators in a formula, drawing of elements in a figure etc.
Three methods may be used to encode these objects:

use a special purpose set of SGML tags to describe the content of the object
use some other, more specialised, language or notation which is compatible with the character set used elsewhere in the document, and then use a special purpose post-processor to generate the object after it has been analysed by the SGML processor.
store the object outside the document, again using a specialised language or notation, and put a reference to it within the body of the document.

The first method can take advantage of the SGML SUBDOC feature, which allows a special purpose Document Type Declaration to be invoked during processing of a text. It also enables the TEI to benefit from work already carried out by other standards bodies and industry groups without the need to attempt an integration of their proposals with ours. Both the Reports of the American Association of Publishers (AAP) and the SGML Standard itself contain detailed proposals for the SGML tagging schemes designed specifically for mathematical formulae and tabular materials Markup of Tabular Material version 2.0 and Markup of Mathematical Formulas version 2.0Bib ref goes here and it would be foolish to attempt to replicate these.
The second method and third methods can take advantage of other, perhaps more appropriate notations which have been developed outside the context of SGML. Examples include `EQN' for formulas or `Computer Graphics Metafile' for graphics. Another SGML feature, the NOTATION declaration, may be used to specify publicly available encoding schemes, which may then be invoked by elements within a document. The content of such elements if embedded within a document are ignored by the parser, within some limits.
The third method is the simplest, in that the object concerned is replaced in the document by an empty element. It also simplifies the task of interchanging documents, in that only one notation will be used in any given object to be transmitted rather than a mixture.
No specific information is provided in these guidelines about the use of either the SUBDOC or the NOTATION features. They are however standard parts of SGML, and therefore may be added to any TEI Document Type Declaration as described in section . Much work needs to be done in assessing the applicability of currently available notations and alternate DTDs to the kind of materials of interest to the TEI, which is left to the second cycle.