Well, not nothing interesting.

I don't think its just the Open source arena, generally I dont know
of any good modeling tools
I only know of three free modeling tools, argouml, tcm and dia.

Dia, seems the easiest to use, and the least sophisticated,
TCM user interface is terrible
Argouml is also very hard to figure out, it seems to try to be smarter than one would want and many features don't work

The main problem I see with models is that you usually want to make models than span an area larger than your screen. Thus printing is necessary, and eventually you throw away the printed paper.

Then you start wanting to include your models in a A4 sized papers to be part of the rest of the design and analysis docs. So you try to take smaller divide your model into smaller part, then the parts and aggregation go out of sync.

Maintaining a set of models, is just hard work, most modeling tools focus more and forcing rules on what you can or can't include in a since models, instead of doing what I want,
composition: glueing ceveral models together to show the overall picture of the design, or information model
decomposition and zooming: allow me to focus on a smaller piece of the model and take pictures of it
Merging: include a model ina work document, a pdf file etc ..., most modeling tools allow to transform a models into a jpg or gif or png, i still mentioned this point to show how important it is, it would be nice thought if the modeling tool can tell me if my jpgs are obosoleted
XML: I would like/trying to write most of my docs, in xml (docbook), it would be nice if I can include few xml lines that will convert into a model, instead of having to draw the models by hand (with the mouse), transform it to a png or gif, and include it as an image in may docbook documen, I think SVG got the potential to solve this problem, but i am not so sure!

Plus, you should really learn more about modeling languages, not all modeling tools support all modeling languages, neither DIA or TCM for example support ORM (the best conceptual information modeling language ever)
Argouml is uml only - and I am not sure how much of uml it support.

Unfortunately, english + some small pictures + an ERD, in 2005 is the best we have (ERD almost directly translate to sql code, this is part why they succeeded)

Actually, this isnt very practical, one of the classic virtues of using a word processor or the tradtional mechanical typewriter, is how easy it is to correct mistakes.

Drawing a model is hard this is why i argued for an XML representation, write its in xml, see it as a picture, using a mouse to draw a model, is not very funny TCM is particularly terrible in this point

Anyway, a model will 1,000,000% evolve over time, and text code enjoys programs like vim, esclipse, and emacs to facilitate cut'n'paste and moving around etc...

Modeling need even more sophisticated tools for editing, not much work done here, drag'n'drop still rule, and its terrible

Actually, more modeling should lead to less code refactoring
So do refactor ur model as much as it needs, dont go cheap, with less sophisticated editing tools, no one would dare changing a model, ppl will keep a model as is, just so that dont refactore it

Which is a terrible reason ...

ORM kinda shines in this points, its designed intentionaly to be easier to extend than a traditional ERD (as in add more content to an existing diagram, not extent the languages itself)

Pencil and papers models, are usually throw away models, and u dont wonna do that, models, should outlive code, if they dont, you are completely missing the point

XML is not a subtitute for UML, I meant to write a model using XML, instead of a graphical editor using drag'n'drop

Actually UML have a standard XML representation called XMI I think

Writing a model in xml, instead of a graphical editor can be compared to designing a webpage in html as opposed to a wysiwig editors

This is what I want, and havent found

I dont want or like to draw diagrams by hand at all, its akward and clumsy

A model is an abstract representation of a system or a solution, being abstract it hides most or all the irelevant details

For most ppl, a model = a diagram

I was told, but I have no clue how, that u can express a model in other ways.

But mainly i just had diagrams in mind, when i was speaking.

a set of diagram notations that complement each other, is also usually refered to as a modeling language, like UML, or ORM or EERD

Again I wanna exploit the moment, to say how much I like ORM [link|http://www.orm.net|http://www.orm.net]

In the agile modeling literature, some have recommended using a digital camera to take photos of diagrams drawn on white boards, they also speak about throw away models

So, it didnt have to be a joke, anyway

In reply to the XML comments, you can draw a UML diagram, and save it in an XMI Xml file, I am saying, I would love to write an XMI file in Emacs, and transform it to a jpg or whatever, or view it in a graphical diagram editor.

It's a lot more practical to write XML docs, than to draw a diagram graphically in a graphical diagram editor.

Plus, if all your docs, are writen in XML (see XML publishing), you diagrams can be integrated in the rest of your docs, instead of being linked as a jpg.