User:SOTO/Forum Archive/Help!/@comment-4139960-20130708231515/@comment-188432-20130710231519

The construction

A waitress was a <whatever>

doesn't directly or indirectly indicate that all waitresses were <whatever>. There is no definition of a which means everything of the class of thing that follows. Instead, a means pretty much the opposite: one of the class of thing that follows. It is a way of individuating one from a group, not applying a common characteristic to a group. In your example, you're saying, "of all the waitresses that exist, this one has the characteristics which follow".

There is nothing grammatically wrong about:

A waitress was a 21st century human who worked at Happy Cook.

However, it's pretty boring writing for a lead sentence. Remember, lead sentences should try to grab the reader's attention. Alternately the lead should economically give us the topic's key relevance to the DWU. That sentence does neither really. A better sentence might be:

A Happy Cook waitress identified Josh and Gary for Gwen during Cooper's Eugene Jones enquiry.