teidata.prefix defines a range of values that may function as a URI scheme name.
Moduletei — The TEI Infrastructure
Used by
Content model
 <dataRef name="token"

<rng:define name="teidata.prefix">
 <rng:data type="token">
  <rng:param name="pattern">[a-z][a-z0-9\+\.\-]*</rng:param>
teidata.prefix = token { pattern = "[a-z][a-z0-9\+\.\-]*" }

This datatype is used to constrain a string of characters to one that can be used as a URI scheme name according to RFC 3986, section 3.1. Thus only the 26 lowercase letters a–z, the 10 digits 0–9, the plus sign, the period, and the hyphen are permitted, and the value must start with a letter.