As GeneXus continues to evolve, now to this new milestone on GeneXus X road called Evolution 2, so do the Knowledge Bases.
The conversion process is taken place when the Knowledge Base is opened with the new version and the significant changes depend on the version where you come from. For instance, if your KB cames from GeneXus X or Xev1 check this article.
Meanwhile, the process to convert a GeneXus 9.0 KB to Evolution 1 (or Evolution 2) is explained at convert to GeneXus X. The main differences with the previous version (GeneXus X) relies on the fact that Evolution 1 supports conversion of Win objects.
For any conversion process, it is advisable to perform an objects navigation comparison.
Links of interest
Following you will find some conferences with information that may be useful in this conversion type.