There's an interesting blog post by Dennis Vorst gone up on the Uniface.info blog, titled Where to put your code. As the title suggests, it's about which places are best for different types of code, based on their content.
There are a number of options; conceptual at the entity or field level, locally at the entity or field level, within the component, a local procedure or a global procedure. All of these have their merits.
I've posted my response, defending the mighty global procedure, but why don't you have a read and add your opinion in the comments?
Summary: Check out this blog post... http://unifaceinfo.com/where-to-put-your-code