Guys, Etna, our new eruptive wysiwyg XML editor, is only in v0.2.5 but it becomes a very nice app... Laurent Jouanneau has spent a long time on this project, on behalf of the Connexions Project, and the app improves every day.

What is Etna ?
Etna is a Wysiwyg XML Relax-NG-based document editor. It requires almost no XML knowledge from the user and we focused on user-friendlyness. We built Etna with the same spirit we built Nvu.
What means Etna ?
It's still a codename. It means Editing Tool for Networked Authors.
Does Etna use the last version of Gecko ?
Not yet. It's based on Firefox 1.0.7 for the time being.
Do I have to pay for Etna ?
Nope. Download and enjoy !
Is Etna open-source ?
Absolutely. Tri-licensed MPL/GPL/LGPL.
Where can I get it ?
Why is it based on Relax-NG ?
Because XML Schemas are another proof of existence of the devil. More seriously, because that's what the Connexions Project needed, and that's the most promising technology in that world. Technically, Etna could be enhanced to be XML Schema-based ; not a trivial work but still feasible at quite low cost.
You said user-friendly and wysiwyg ?
Yes. If there's one thing Microsoft has shown very well with Infopath, it's that XML can be hyper-successful when XML is hidden. In other terms, don't show the markup, don't show the technical complexity. Complexity is for the programmer, it should not be for the user under ANY circumstance. So we hid the complexity without dropping the power.
You said a while ago that you had to extend Relax-NG ?
Yes. Because Relax-NG is definitely not enough for Wysiwyg editing. That's an old problem. I remember discussing this problem about SGML DTDs with Jean Paoli back in 1993. And the problem was already old at that time. But nobody has ever worked on it because most SGML/XML gurus think Structured Documents and Wysiwyg Editing cannot coexist. We tend to disagree :-) So we extended Relax-NG and you can read about it here.
Could these extensions become a standard ?
Standards are good, very good. We found "a" solution to an old existing problem. We don't say we have "the" solution. And we have many more ideas about what's missing in schemas and DTDs that are not implemented yet. So we're absolutely open to discussions, standardization and we will update our app to match the resulting compromise when/if a standard emerges.
What's cool in Etna ?
You can add a stylesheet to the schema and that one will be used only editing and it won't appear in the document when you save it. When you create a new document based on given schema, you can select the "blank document" you want if the schema specifies more than one. Schemas can be distributed in XPI form or just as a normal file. Each XML element or attribute can have a description and a short description and these can be easily localized through standard Mozilla properties files. Documents loaded/created/edited by Etna are always valid. The Relax-NG validator is the root of Etna and it's strictly impossible to do something invalid. Of course, Etna is extensible and you can add your private chrome to Etna's main UI (for instance a specific toolbar for a given schema). Attributes are edited in a sidebar and this attribute editor conforms to datatypes specified in the schema. And more !!!
Can we edit SVG in Etna ?
 Not for the time being since Etna is based on Firefox 1.0.7, but in the future, yes, absolutely.
Can we edit MathML in Etna ?
Can we edit XUL in Etna ?
There's is nothing against it, really, but designing a user-friendly not-too-geeky UI to do that is a real challenge.
I want to submit a bug report/RFE, do you have a Bugzilla for Etna ?
Yes we do.
Could you extend Etna for our specific corporate needs or help us with our corporate Schemas/DTDs ?
Yes. Please contact us.

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