2. The DALF DTD

Many of the features encountered in letters can be encoded with the TEI scheme. However, the TEI tagset has some generally acknowledged lacunae regarding the encoding of primary source material. Chapter 18. Transcription of Primary Sources of TEI P4 concludes with a hint at future expansion of the TEI tagset in this respect. Apart from items that are applicable to primary manuscripts in general, there are some aspects of a collection of digitally encoded letters that are not covered by the TEI encoding scheme. Fortunately, the option is provided to extend the TEI scheme.

In doing so, we opted for a close structural and terminological resemblance with the TEI tagset when constructing the DALF DTD. There are a number of reasons for this approach:

• To guarantee compatibility with TEI documents, and thus provide users that are familiar with the TEI scheme with an intuitive instrument to mark up correspondence material.
• To present DALF as a true TEI extension, that may enable a substantial evaluation in the light of the TEI tagset, and maybe one day be integrated as an auxiliary tagset for letters in the TEI tagset.
• To guarantee that DALF encoded letters are TEI-conformant documents, as specified in chapter 28. Conformance of the TEI P4 Guidelines).

Therefore, the DALF DTD has been specified as a customisation of the TEI DTD in the way specified in chapter 29. Modifying and Customizing the TEI DTD of the TEI P4 Guidelines. The extensions and modifications are encoded in two separate files, DALFExtns.ent (for selection and modification of existing TEI tags and element classes) and DALFExtns.dtd (for declaration of new elements and attributes), which were input to the Pizza Chef program on the interactive TEI website, producing the DALF.dtd file. Besides the declaration of new elements and attributes in those modification files, a selection was made of some subsets of standard TEI elements. Elements from the TEI tagset are included in the DALF tagset along the following parameters:

• a ‘mixed base’ tagset was selected, consisting of the prose and drama bases
• elements from the additional tagsets Linking, figures, Analysis, transcr, textcrit, and names.dates were selected
• the entity sets ISOlat1, ISOlat2, ISOnum and ISOpub were selected

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The practical application of the DALF tagset will require choices of the encoders, regarding the level of detail in the meta-descriptions, and between alternatives to mark up certain phenomena in the source material. These guidelines are in the first place conceived as a descriptive presentation of the provisions made in the DALF tagset to mark up correspondence material. Although alternative encoding approaches are signalled in the guidelines, it is left up to the encoders to develop a preferred practice. To reduce contingency in the encoding of different letters and/or editions, the encoder should

• keep a consistent approach to encode the same phenomena. Minimally within each letter separately, but preferably within all letters of an edition.
• document the approach taken within the <encodingDesc> element in the header of each letter.