SharePoint content types and columns share a one-to-one relationship with OnBase Document Types and Keyword Types, so mappings configured at the SharePoint site level are inherited by any child sites.
For example, if you create content type B and base it on content type A, any columns that content type B shares with content type A automatically inherit their column mappings from content type A. If content type C is a child of content type B, then it automatically inherits column mappings from both content types A and B.
If you have configured any mappings at the site level, you can override them by mapping different Document Types at a child level. However, column-to-Keyword Type mappings cannot be overridden. To map different Keyword Types at a child level, do either of the following:
In SharePoint, create a new content type with new columns to map to OnBase Keyword Types.
In OnBase, create a new Document Type with new Keyword Types. Override the inherited mapping with the new Document Type.
See the SharePoint help for information about creating new content types and columns.