Who really defines what is a CMS?
You do.
I'm more convinced than ever that CMS experts aren't really in the driver's seat when defining the content management system. Experts in the field of content management are more or less observant passengers that are there to help you not get lost and to point out the significant landmarks on the way. This journey takes you to places while you the customer remain in the driver seat with all the privileges and responsibilities of being the driver.
Over the past few years I've realized that my work preference is to keep things as simple as possible. Sometimes when defining information systems keeping things simple works while other times the system is new and remains too complicated to define. Thanks to my reply in a productive rant against CMS by Laurence Hart I'm not only understanding my aversion to being called a CMS expert but also my philosophy and role in defining what is a CMS. This personal philosophy is developing...
Scott Abel convinced me a few years ago on my own blog that the definition of a CMS is never static and always changing. We’re chasing our own tail when we get nit picky in our definitions of a CMS. Somewhere in all the marketing that has been done for terms such as CMS, ECM, and WCM…we have forgotten the difference between information system and information technology.