The certification service database should keep a record of certified software products and their versions. Records of certification request runs should also be kept. In addition, the handling and resolution of problems might add records to the certification service database. If the number or severity of problems for a particular product and version exceed a threshold the certification of that product might be suspended.
On One possible feature that might be considered with such as service is a certificate identification that is passed with each data record submitted. If the certificate identified is suspended or otherwise invalid the data record could be rejected.
Ongoing certification implies that a product vendor could and would run certification tests on their product from time to time. The test mechanism will need two modes. One would be a test mode that the product vendor runs against as they develop and refine their product. The other would be an official certification mode that would keep a record of the certification run.