Inscriptions are obviously subject to all kinds of damage and wear, and therefore it is quite common for pieces an inscription to have broken off, or for sections of writing to have become illegible. In addition, there are a number of features of the inscription itself that may bear notice by an editor: the text may contain abbreviations that warrant expansion, or a name may have been erased in antiquity and perhaps a new name inscribed on top of the erasure. In addition, there may be aspects of the editorial history of the inscription that are worthy of note. For example, a previous editor may have recorded letters that are no longer readable. These and other features of inscriptions (and papyri) are noted in the published versions using in-line marks. For example, missing text will be marked off with square brackets “[...]”. If the missing text can be supplemented, it will go inside the brackets. Letters that are worn or damaged and cannot be read with 100% accuracy will be marked with a dot underneath. The expansion of abbreviations is marked with parentheses, so “co(n)s(ul)” for “COS”. Text deleted in antiquity will be marked with double square brackets, “[[Getae Caesari]]”. Words read by a previous editor but unreadable by the present one are underlined, “Imperator Caesar”.

Leiden was designed as a typographic standard. It specifies how an edited inscription should look in print. The “data dictionary” for Leiden consists of a number of published articles and the substantial body of practice. So there are places one can go to find out what a particular epigraphic siglum means. There are, however, a number of problems that present themselves immediately when one attempts to represent Leiden digitally. These include underlining text, which is implemented differently in different software, the use of characters that are not widely implemented in standard fonts, the inconsistent rendering of features like combining dots below the line, and abbreviations where the abbreviated word is not marked. These difficulties were one of the motivations behind the creation of the EpiDoc XML standard for digitally encoding inscriptions.

EpiDoc, despite being an XML standard that covers much of the same ground does not, and never did intend to replace Leiden, which is a familiar format for epigraphers and has the advantage of being more terse and compressed. The EpiDoc team saw a need therefore for infrastructure to convert Leiden to TEI EpiDoc and back again. The latter transformation can be accomplished with XSLT, but the Leiden to EpiDoc conversion necessitated the creation of a tool called the Chapel Hill Epigraphic Text Converter. This tool uses a series of regular expressions to convert Leiden into a well-formed XML. The regular expressions not only convert the simplest inline code (i.e. Leiden underdot to EpiDoc <unclear reason="undefined">) but also deal with specific project-related issues and prepare more complex code to be processed by a final XSLT that completes the transformation.