The Central Credit Committee (German Zentraler Kreditausschuss / ZKA) is an industry association of the German banking industry. It was renamed to Die Deutsche Kreditwirtschaft (DK) in August 2011
The user guides can be found from ebics: http://www.ebics.de/index.php?id=77
Validator has pipes for version 2.6 and 2.7
DK SEPA Credit Transfer v2.6 DK SEPA Direct Debit v2.6 DK SEPA Credit Transfer (CCT) v2.7 DK SEPA Direct Debit CORE (CDD) v2.7 DK SEPA Direct Debit COR1 (CD1) v2.7 DK SEPA Direct Debit B2B (CDB) v2.7
DK uses a stripped version of ISO 20022 schema. This means myriad of institution specific rules are already limited from schema level, and using elements which would be ignored in EPC pipes will cause a failure from schema level in DK pipes.