The sole purpose of the <body> of a class 1 file is to contain a segmented transcription of a single version of a single work from a scriptum. <body> may take @in-progress and must take @xml:lang.

<body> takes one or more <div> elements, each of which either govern other <div> elements, or govern text (and perhaps TEI markup).

This tree of <div> elements, along with each one's @type and @n values, structures the text according to the reference system that has been adopted (see the section called “One reference system”).

The term leaf div refers to those <div>s that contain text and therefore no other <div>s.

<body> must take @xml:lang, declaring the main language of the document. If a change in language occurs, you should ensure that the @xml:lang value of that <div> (explicity or by inheritance) reflects the majority language.

Within this treelike structure of <div>s, the concatenation of @n values, starting from the most ancestral <div>, provides the flat ref, and is the heart of identifiers it TAN, particularly in class 2 files.

One of the most important validation rules is the Leaf Div Uniqueness Rule, which states that the flat ref for each leaf <div> must be unique.

Take for example a work that is structured into books, chapters, and finally sections. If you are told to find book 3, chapter 7, section b, line 5, you should be able to find the one place where that applies. There should not be two passages labeled 3.7.b.5.

This rule applies only to leaf <div>s and not to <div>s in general. That is because there are some cases where a source have a major textual unit punctuated by another. For example, chapters 24 and 30 in the book of Proverbs of the Septuagint are split and interleaved. The sequence goes as follows: 24.1 - 24.22e (22a - 22e are verses not extant in the Hebrew); 30.1 - 30.14; 24.23 - 24.34; and 30.15 - 30.33. If the uniqueness rule applied universally, this kind of reference system would be impossible.