12.3. Attribute classes
An attribute is extra information attached to an element, written inside the start tag, such as xml:lang, xml:id, or type. An attribute class is a reusable bundle of attributes that many elements share.
Elements carry the main structure, for instance: <form>. Attributes add details which qualify the given element, for instance: <form type="lemma"/>. An attribute class is a shared standard set of such details that TEI and Lex-0 apply consistently across many elements, for instance: att.typed
Attribute classes help TEI and Lex-0 ensure that common metadata (identifiers, language, linking, typing) works the same way across the vocabulary, avoid repeating the same attribute definitions on hundreds of elements, and support predictable processing.
In day-to-day practice, lexicographers and encoders will most likely focus on which individual attributes are allowed within each individual elements. But if for any reason you want to understand how attributes function across elements, attribute classess will become your friends.
