If you have old records in DC (or OLAC, a linguistic extension of DC) you can use the following profile: OLAC-DcmiTerms
From that profile you can generate the XSD: http://catalog.clarin.eu/ds/ComponentRegistry/rest/registry/profiles/clarin.eu:cr1:p_1288172614026/xsd
And then you can transform your DC XML files into CMDI files that comply with the profile with the following XSLT: olac-cmdi
An example (DC) inputfile: oai_ota_oucs_0001.xml
The corresponding (CMDI) outputfile: oai_ota_oucs_0001.cmdi