I came across [a question about a data type for MD5 values](http://dba.stackexchange.com/questions/115271/what-is-the-optimal-data-type-for-an-md5-field). The recommendation in that question states using `uuid` as type for that field.

The argumentation is solid. But I find that this might be confusing to someone unaware of the points revealed in the above question. The decision to use `uuid` as MD5 type is something that I would like to see in some form of documentation in any project that does this.

As a "helper" to whoever looks into the DB Schema, one could argue to create a `md5` domain inheriting from `uuid`. That way, the column types would be much more explicit and the intention would be much clearer.

But it would use a domain for no other reason than to "rename" an existing type.

It's still something that would make sense to document properly. But that documentation could be centralised to a section explaining the domains in the DB. So you wouldn't gain anything in terms of documentation. The advantage I see is, as mentioned, that the *intention* becomes clear when looking at the table DDL.

Are there any downsides to this?