GUI designers! - got suggestions for a GUI modelling diagram language?

Question

Refering to this question I asked a while ago:

UI functionality modeling languages

It looks like there is no good-enough solution. I decided to develop one. (and prepare a set of elements for DIA or something) I'm sure it will require a good insight in peoples' experiences and problems in designing functionally complicated GUIs.

I've got some ideas already, but I'd like to hear from You what You'd expect from a GUI functionality modelling language.

Clarification: It's functionality modelling (possible user interaction, events etc.), so it's not about where I put a button. It's about objects that have some events binded, and the interface behaviour logic.

If You think (just as I do) that UML is far from useful for such purposes - feel free to put Your expectations here. I'll try to meet them. ( not necessarily in person;) )

Remember - there is no such thing as a wrong answer to this question

Answer 1

I would want four things in a UI modeling language:

1. A definition of the UI objects (controls, forms, etc.), including: a. The composition of the UI objects from UI primitives and sub-controls (members). b. Events c. Properties d. Methods
2. The ability to layout said objects. I know you're only wanting to cover functionality, but the main purpose of models is the ability of humans to understand them, and the most intuitive way to do so is to "see" the UI. The layout could just be a conceptual "design-mode" thing divorced from the actual UI.
3. Discrete states (modes/configurations) for UI objects. Each state results in a different set of properties for the UI elements. For example, you may have rules that when you're in the "Downloading" state, most controls are disabled, a progress bar is shown, and the only clickable object is a cancel button.
4. Unless you're just modeling a control library, I'd want modeling for the "orchestration" of the UI elements within the scope of an application. For example: a. How the UI is data-bound to the model/view model/presenter b. How business logic/controller methods are tied to UI events c. Perhaps use cases with interaction sequence diagrams could fit in here