Thanks, Eric. I didn't know about that MODX explanatory site.
Brian, a subsystem purporting to be a content manager ought to have a lot of interesting & useful aspects. Various users will regard these aspects from their own points of view. So I can't provide a good, concise answer to the question "How does MODX work?" I can tell you how it appears to me, however.
MODX runs on hosting services that provide a LAMP stack. In particular, MODX depends upon the object-oriented features of PHP version 5.x. So it doesn't work with Coffee Cup's S-Drive, at least in its current incarnation.
From a Web developer's point of view, MODX provides core functions and extensions that allow inline substitutions of references to resources (text, images etc.), static HTML chunks and so-called "snippets" written in PHP. These snippets are safe & secure to use. They can be nested, just like function calls. As a conceptual shortcut, think of old-school Cold Fusion functions, except completely source-code visible and modifiable by the developer.
A MODX page template is just static HTML, related CSS and perhaps Javascript. This makes it easy for a client to buy an attractive "look" off of the Web to which the developer adds content and dynamic behavior using MODX. This can be as simple as substituting a MODX resource reference for the template's "Greeking" text.
MODX solves the site navigation problem almost trivially (as a content manager had better do) with a snippet called "Wayfinder." I wouldn't embark on a project of more than four or five pages without using MODX because Wayfinder keeps all the inter-page links straight as the site evolves.
MODX caches page templates, resources and snippet results by default, making for quick page loads. However, it's possible to require non-cached evaluation of one thing or another at each page load, if required.
MODX includes a back-end manager for updating and extending the site. Access is password protected, with roles such as "designer," "administrator" and "content provider" available to control privileges. There is talk of adding workflow management, but so far, just talk.
MODX provides for event-driven plug-ins, too. So far, I've avoided learning about this: Someone else in the MODX community had already developed the things I happened to need.
MODX does a great job of separating site content, layout and styling from one another. As such, it plays fine with Coffee Cup's client-side UI and responsive design tools. The word for which I am groping may be "orthogonality."
I'd be delighted if Coffee Cup were to champion something like MODX. However, it could be can of worms to support across a wide range of user sophistication and interests, so I can understand their reluctance.
Does that make sense? Other questions, Brian?
halfnium -AT- alum.mit.edu
Yes, I looked just like that in 1962.