The internal structure of each <witness> (testimony to which we will refer from the critical apparatus of our edition), must be carefully respected:

<witness xml:id="D">
	<abbr type="siglum">D</abbr>
	codex Collegii S. Iohannis apud Cantabrigienses D 12 saec. X/XI
</witness>

<witness xml:id="Alton1923">
	<abbr type="siglum">Alton 1923</abbr>
	<bibl>
		<author>Alton, E.H.</author> 
		<date>1923</date>
		<title level="a">Notes on the <hi>Thebaid</hi> of Statius</title>
		<title level="j">CQ</title>
		<biblScope unit="vol">17</biblScope>
		<biblScope unit="pp">175-187</biblScope>
	</bibl>
</witness

• They must always have as @xml:id the siglum that corresponds to it, if it is a manuscript, and the author's surname if it is an authority. The @xml:id must always be unique, they cannot be repeated in the same document. Each witness must have an exclusive abbreviation. It will be to these @xml:id that we will refer to from the entries of the critical apparatus.
• First it is inserted the tag <abbr>, where the siglum or the author's surname will be placed exactly as we want it to appear visible in the published edition. This <abbr> will always have the unique attribute @type="siglum", to differentiate it from other types of abbreviations inserted in the commentary or in other parts of the edition.
• If the siglum that identifies the manuscript is a text for special formatting (contains superscript or subscript, or is written in a special type of alphabet, etc.), see the explanation in the chapter Sublists and manuscript variantsThe list of formats of a special nature that can be added within <abbr> can be found in Formatos de carácter <hi>.
• In the node of the tag we place succinctly the name of the manuscript, its location and its dating, always in Latin, or the bibliographical reference of the work cited within a <bibl>, with the structure described in Bibliographic References.
• If the witness is a modern work, it is always useful to add in the <abbr> and in the @xml:id of the <witness> the year of publication after the author's last name, especially if several of their works are cited.