Extending the TEI DTD

You can also add your own customizations to the TEI DTD. Any additions to the DTD can be done in the DOCTYPE declaration. To add to the list of acceptable attributes for an element, for example, you can add a statement like this to your DOCTYPE statement:

<!ATTLIST xref url CDATA #IMPLIED >

The most common extension is the addition of entities, like this one for an e with a tilde over it:

<!ENTITY etilde  "&#x1EBD;" >

If you have a lot of modifications, TEI has a parameter entity included that allows you to put all of these in a separate file. Once the file has been created it can be declared in the DOCTYPE declartion like this:

<!ENTITY % TEI.extensions.ent SYSTEM 'myTEIextensions.ent'>