dbschema and documenting tables/columns

I need suggestions for documenting an Informix database I support. It has been modified greatly since it was first created. I used the dbschema utility to create a fresh schema. The problem is the orignal sql files contained lots of valuable documentation. Is Informix self-documenting (meaning you can add descriptions somewhere in the database), or can someone suggest a method where I can make it self-documenting? (or I'll invent my own...) I'd like the descriptive info to be part of the database, not a separate file that must be maintained. Judy