I feel like a broken record whenever CMSs are mentioned on DC, so please excuse me while I climb on my horse.
- How is the plugin/extension system designed?
ModX is basically a framework, one of it's greatest features are the use of what they call chunks and snippets, a chunk is simply a piece of html and a snippet a piece of php code. These pieces can be inserted anywhere in to your template which makes life incredibly easy. Extensions/addons are usually just a collection of chunks and snippets. One of the features added for Revolution 2.0 was a transport system that means you can easily build a package that can be simply installed by the user.
Plugins, separate again, can be event driven, for example before or after a page is rendered. When the event happens, so does your plugin.
- How is the installation system designed?
Most CMSs I've had experience with are pretty much the same, you have a wizard based interface that does a few pre-req checks, gets the database info and then executes a sql script to create the tables and update any config files.
If, however, you go with their cloud offering
(yes, they do have a free dev account), installation is done in seconds at the click of a button.
- How are users, and more importantly GROUPS of users represented in the database?
In Evolution 1.0, users and groups were a bit strange but in Revolution 2.0 they've gone for ACLs
. It can be a bit much to get your head around when coming from the old way, which was strange, but simple. But I find that it makes more sense.
As for the database structure, to me it makes sense.
Users are in a table that is pretty much just username and password.
An attributes table contains the other bits and pieces like email, phone, etc.
Then a groups table that contains the groups you've defined
and a table that links users to groups as a user can be in more than one group.
- How is the permission system handled?
are a collection of policies, the policies define what a user can and can't do, like edit a document, view certain menu items.
- How is upgrading handled?
Download new package, upload to host, re-run setup, wizard handles the upgrade process.
Via ModX Cloud? click a button, done in seconds.
- How are hooks and events handled?
As mentioned above in relation to plugins. Certain events are defined, when you create or install your plugin you select which events will trigger your code.
- How is translation handled?
Revolution 2.x really went all the way with this. There is full lexicon management, you can change any word you like.
So to start with, all words are seperated into namespaces for various parts of the system.
In the lexicon directory you have a folder for each language and each language has a set of php files which define the value of each string... eg
On top of that any changes to the default lexicon are stored in the database, meaning you can revert any change quite simply and if you want to call documents Bananas, then go ahead and do so.
The api has a logging method which logs to a file, you can call the method with flags like error/warning/info from any of your custom scripts. The log file can be viewed/cleared via the management intercace.
- How is security handled and what kinds of options exist for monitoring and dealing with problems?
This is more a process kind of question I'm guessing. The team seem pretty committed to squashing vulnerabilities, I'm not sure what monitoring goes on internally.
- What kind of support for versioning exists?
Out of the box, none really, but as with most things in the CMS world, there is an Add-On available
- What kind of choices were made about what to build into core vs. what to write as extensions?
I like this question, because not every CMS can be for everybody so a line has to be drawn somewhere as to what's included out of the box and what gets bolted on afterwards.
First and foremost, ModX is a framework, what it does out of the box is give you incredible flexibility.
One of the things v1.0 did poorly, was blogging, out of the box, 2.0 is not too crash hot either (ie. it's not wordpress), but one of the lead developers wrote and add-on. Install it, and bam, now you have full on blogging.
Another thing left out of the box in 2.0, TinyMCE, because you don't have to use TinyMCE if you don't want to but it is the most popular addon download.
I hope that's piqued your interest, feel free to ask me more technical/direct questions on any part you wish to know more about.
All of this info is drawn from my personal experience, I'm just an avid user who's been developing web sites with all sorts of crazy requirements since I first discovered ModX in 2008.