This repository tracks changes in the versions of the schema by the Charters Encoding Iniative (http://www.cei.lmu.de).
The cei.xsd in this repository is considered the main reference. cei060122.xsd is a legacy file representing the status of the work in 2017. CEI.dtd is the original very generic Document Type Definition meant to reflect the original tag library from www.cei.lmu.de.
The work on the CEI is in progress to be merged into the main TEI P5 branch with the CEI2TEI proposal. See TEIC/TEI#2376 for the ongoing discussion on this. The definition here will be kept for legacy reference.