I couldn't find a list of web-based ontology editors. a) Which options do I have in general and b) Which tools fullfill the following requirements:
only browser (with JS or Flash) required
open source
complex axioms can be defined (e.g. existential restrictions), inverse properties, ...
instances can be input conveniently
configurable appearance with style sheets
supports rights management
(optional) suggestion and management of changes
I had a look at Web-Protégé, which looks quite good, and I will probably use it. However, I am a little bit worried that they still use GWT 1.7. Nevertheless, there is very recent active development. Is Web-Protégé without alternative?
In my case the editor instance that I would like to set up is intended to serve as online documentation as well as a possibility for others to contribute to a collaborative version of the ontology.
There's the Knoodl tool available from Revelytix. It ain't open source, but they do have some other features that support collaboration and whatnot. Never used it myself, but have heard good things about it.
I gotta ask: why the focus on web-based tools? You're doing data modeling. What's your use case for having it in the browser vs. something like Protege, which is quite good?
You should look at TopBraid Ensemble, in addition to TopBraid EVN, for broad-based ontology support from a browser. It's not a full OWL editor, but neither are some of the alternatives you mention. If you want to lower the barrier for participation, I'd generally agree with @RobGonzalez that exposing a full OWL editor may not be a common use case. With Ensemble, you can customize an application to support model editing without requiring that the user know all details of RDF, OWL, etc. I.e. you design a domain-specific application that just happens to use ontology modeling in the background. If some modeling constructs need to be edited, then these can be added to the application.
The NeOn Toolkit is the ontology engineering environment originally developed as part of the NeOn Project and now supported, together with other technologies from NeOn, by the NeOn Foundation.
The NeOn toolkit is a state-of-the-art, open source multi-platform ontology engineering environment, which provides comprehensive support for the ontology engineering life-cycle. The toolkit is based on the Eclipse platform, a leading development environment, and provides an extensive set of plug-ins (currently 45 plug-ins are available) covering a variety of ontology engineering activities, including Annotation and Documentation, Development, Human-Ontology Interaction, Knowledge Acquisition, Management, Modularization and Customization, Ontology Dynamics, Ontology Evaluation, Ontology Matching, Reasoning and Inference, and Reuse.