Lothar Scholz wrote:
> CH> Good move not starting on the GUI, but you need to start even further
> CH> back, with a conceptual data model. The API is then a simple consequence
> CH> of the data model.
> No i don't agree here. The UI and the way to present data, has such a huge
> influence that it must be considered in every development cycle.

Yes, and no. You are speaking from the biassed perspective of the kind
of data models that databases implement directly - basically ER models.
Those are often badly constructed, because the ER model isn't rich
enough to catch the conceptual model, and performance often demands
that salient elements must be compromised even when they could be
represented in the ER model. The other problem with ER models tends to
be that the object modellers get to drive the process, and then go to
the DBA's and say "here's our data, find a way to stash that". Object
models are commonly even worse than ER models at catching the conceptual
structure.

Conceptual models on the other hand, always reflect the flow of a good
user interface, and vice versa. This is for the simple reason that they
represent the mind map of the user. Every action in any UI is one or
more steps along the arcs of the conceptual model. Whether the designer
ever wrote the conceptual model down or not, the arcs are there in the
semantic space, and so are the objects they join.

> And adding a user interface on top of a existing data model allways
> result in too much restrictions.

No. Adding a user interface on top of a data model *that does not
reflect the conceptual model* does that. Learn to construct proper
conceptual models, then to map them to ER models and object without
forgetting the original conceptual model, and you'll find it all
comes out beautifully, every time.

Read more about Object Role Modelling at www.orm.net and related
sites. I've been following Terry Halpin's work for 18+ years now,
and he's an excellent fellow, even if his company did get acquired
first by Visio then Microsoft, where he now is. There's a good video
introduction to ORM by him and otherson one of the Microsoft DotNet
sites, check it out, very enlightening.

> And by the way, Hal, the knock out criterium for the first tycho
> version was the non available multi dimensional classification. When i
> download such tools and only see a simple tree,...

My description of aspect-oriented modelling is an attempt to address
exactly that problem. It isn't covered by any formal literature, AFAIK.

Clifford Heath.