Critical CMS features

It might seem that we have now defined a CMS as a system for managing content on the Web. That would be to look backwards rather than forwards, though. In retrospect, it is apparent that one of the limitations of systems like Mambo is that their design is geared too heavily to handling documents. While every website has some pages of text, few are now confined to that. Even where text is primary, older systems are pushed to the limit by demands for more flexibility in who has access to what, and who can do what.
While the so called "core" Mambo system could be installed with useful functionality, an essential part of Mambo's success was the ability to add extensions. Outside the core development, numerous extra functions were created. The existence of this pool of added capabilities was vital to many users of Mambo. For many common requirements, there was an extension available off the shelf. For unusual cases, either the existing code could be customized or new code could be commissioned within the Mambo framework. The big advantages were the ability to impose overall styling and the existence of site-wide schemes for navigation and other basic services.
The outcome is that the systems have outgrown the CMS tag, as the world of the Web has become ever more interactive. Sites such as Amazon and eBay have inspired many other innovations where the website is far more than a compendium of articles. This is reflected in a trend for the CMS to migrate towards being a framework for the creation of web capabilities. Presentation of text, often with illustrations, is one important capability, but flexibility and extensibility are critical.
So what is left? As with computing, generally, new ideas are often implemented as islands. There is then pressure to integrate them. At the very least, the aim is to show users a single, rich interface, preferably with a common look and feel. The functionality is likely to be richer if the integration runs deeper than the top presentation level. For example, integration is excessively superficial if users have to authenticate themselves separately for different facilities in the same website. Ideally, the CMS framework would be able to take the best-of-breed applications and weave them together through commonly-agreed APIs, RESTful interfaces, and XML-RPC exchanges. Today's reality is far from this, and progress has been slow, but some integration is possible.