Read/write access to the MySQL db outside of MODX?

Could this be viable or problematic?
FileMaker Pro has been supporting External SQL Data Source r/w since 2007.

Writing seems to be risky in Drupal according to the source below.

Please see:
http://proofgroup.com/blog/2008/nov/filemaker_ess_read_dont_write

http://www.filemaker.com/downloads/documentation/techbrief_intro_ess.pdf

With MODX Revolution, you should never write to the database directly. The application handles the business logic required to properly write the data.

Thanks for the swift answer.
Sorry, I wasn’t very specific; I’m using Evolution as of now.

I realize that there is a proper way of writing to the database, i.e. through MODX.

BUT, if updating the db from another interface still would be much needed, what are the real risks involved, and could they be avoided, e.g. by never touching structural data such as the Resource ID?

Evolution does not have a business-logic layer in the same way Revolution does, so this does not apply. You will likely need to write directly to the database for Evolution, but you’ll have to be aware of what every piece of data is for.