Confluence is a wiki-like tool developed by AtlassianSoftware in JavaLanguage.
http://www.atlassian.com/software/confluence/
At my work, it was introduced by ThoughtWorks consultants. To me it seems quite overengineered, with features like:
Interestingly enough, those things described here as 'overengineered' are three of Confluence's most popular features. Some people just think in trees, so we have page hierarchies. I was doing a demonstration yesterday to someone in HR, and "Is there any way to put this page underneath that one?" was one of her earliest questions. Meanwhile, when I gave this demonstration I'd been required to leave my phone at the front desk, just because it contained a camera. A wiki with no security (or no ability to partition security) simply wouldn't have been an option.
Confluence is a commercial product that has to compete with the several hundred available free wiki implementations. If all somebody needs from their wiki is provided by Instiki, they'll install Instiki regardless of what we do. Since we can't compete for that market, we instead add a bunch of features (and eye-candy) that the Instiki user would call 'overengineering', but that our customers are willing to pay to have. -- CharlesMiller (a Confluence developer)
I find Confluence one of the few wikis capable of straddling useful and professional, and those three features are absolute requirements. The hierarchical ability allows me to create 'real' documentation that is still capable of growth.
I find that the features of Confluence get in the way of many of the benefits of a Wiki:
Unlike that previous post the usage of NameSpace in a corporate Wiki like confluence tends to be very useful as you can organize the spaces by project and avoid NamePageClash? that would either require you to emulate the NameSpace through the PageName or create multiple wikis. The wiki we're currently using does not handle NameSpace and it is preventing us from putting more information onto it because different projects (and clients) will use PageName for different purposes.
A namespace per project is exactly the scenario that caused the most problems. Technical information that should have been shared between projects was duplicated, incompletely, in each project's space. In a flat wiki, people would have been refactoring the duplication away and a lot of duplication would have been avoided because of fortuitous linking, but spaces act as a social and bureaucratic barrier that stops both those things happening.
This isn't a complaint specifically about Confluence (although the other three complaints are). The same problems occur in any wiki that is not flat but tries to impose a hierarchical structure onto the information's natural graph structure, especially when there's an administrative overhead in creating new namespaces and the hierarchy mirrors the organization rather than the information itself.
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I have found Confluence and the support from Atlassian to be one of the worst I have ever suffered.
Being a Widows shop, they are not able to give any meaningful support for UNIX, being somewhat Tomcat based, they are seriously mystified with problems with other sorts of application server. The support pages are badly thought out and a mish-mash of off-the-cuff, add-hoc bemusing non-sequiters; vital details are mislabled and hidden in documents with the wrong title. In one page I found 6 errors that meant that their installation instructions could never work. The tails of comments from users seem to be a combination of breathless wonder (the wonder being it worked at all) and pseudo intellectual waffle.
On their web site there is reference to the 'Legendery' Atlassian support. I have to assume 'Legendary' means 'mythical' in this context. When something goes wrong all the staff can do is point you to pages in their wiki (without so much as a rossetta stone, dammit) that you have already read and waste time. I point out I got only one message a day from Atlassian, and some of my support calls went untouched for 5 days.
As an example of all that is wrong with a wiki (not being specific to confluence) the pages demonstrate that just because anyone can write a page, it doesn't mean anyone can write one well.
Of course, none of this means Confluence is a bad product. It is, however, commercial, and the ability of the support staff to support the product in a timely and knowledgable fashion is the clincher here.
After my experiences with Confluence and Atlassian (and my co-workers with Jira) our company refuses to support it with any SLAs. No fixed delivery times are given, and all support is 'best efforts' only.
If you use confluence, use windows and Tomcat. If you use any other operating system, or any other application server, use something, indeed anything, else.
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Atlassian here - if you receive poor support then please call us immediately and we'll jump on the problem! We've made huge improvements to support recently including more than doubling our support staff and technical writers, though it has taken us a while to adapt to the fact that our customers _more than doubled_ last year as well and that growth isn't slowing down. We rotate actual Confluence developers onto support and you can't get any more qualified than that.