A very short article, or a simple article such as an editorial or an obituary, may contain nothing but paragraphs and other paragraph-level elements such as figures and tables. But most journal articles are divided into sections, each with a title that describes the content of the section, such as “Introduction”, “Methodology”, or “Conclusions”.

Sections are recursive, that is, various levels of sections are indicated by containment, not by different names for the subsections. A <sec> element may contain lower level sections that are also tagged using the <sec> element, not tagged explicitly as <sec2>, <sec3>, or <subsec1>, etc.

Untitled Sections: In previous versions of this Tag Set, a <title> element was required on each section. A title was considered to be the basic requirement for producing an automated Table of Contents for online viewing of an article, so a title was required. However, as nice as it would be to keep that requirement, this is a conversion target Tag Set, and there are at least two circumstances that lead to “title-less” sections. Conversion experience has shown that some publishers allow loose paragraphs between sections, and the most logical way to handle these paragraphs is as the content of untitled sections. Tagged documents have also been seen in which an article has been made to “look right” by creating the look of a heading using <bold> inside an otherwise empty paragraph, rather than using a real title or heading element. So, in this Tag Set, the model for section (<sec>) has been redefined to make the elements <label> (for example, “4.1.1”) and <title> (for example, “Temperature Inversions”) both optional. It should be noted that without true section-level headings it will be difficult to create automatic Tables of Contents and high-quality web and print displays.

Common Practice: The <sec> element can be used within <back> to tag material that has not been explicitly named as one of the other back matter components, that is, it is not named as an appendix, an acknowledgment, a glossary, etc. For example, tables are frequently placed in the back matter, with no other designation than a label such as “Table 6”, or a title such as “Epochs of Geologic Time”.