Re: Conceptual, Semantic, Syntactic and Lexical Design

>
> It's not the conceptual modelling I was having trouble with. It
> was the
> functional/semantic level (the one below conceptual).
Perhaps because Steve Feiner has a strange version of it in his slides.
He has it as the operational semantics of the conceptual level, and ends up with a completely
system-centred approach.  His conceptual level is wholly a set of system concepts.
>
> I don't see use cases as an alternative to conceptual models - the two
> compliment each other. I do believe, though, that if the entities that
> users need to concern themselves with (from the conceptual model) are
> not obvious in a UI, the UI is unlikely to be effective.
Use cases imply a conceptual model, better to pull it out and make it explicit,
but better still to start with something useful!  Objects are implicit in usage but not vice versa.

>
> BTW, how does an ER model differ from a conceptual model (I describe my
> conceptual models as ER diagrams sometimes so I really am interested!).

ER diagrams are one possible representation of a conceptual model.  However, they fail to
capture all sorts of things that, for example, TKS does cover, such as typical objects and
similar elements that are useful in design.

Concepts are by their nature invisible and intangible.  They are in people's heads.  We can only
assess representations in terms of comprehensiveness and expressiveness.  ER diagrams can't
express the full range of human knowledge, but they are a useful skeleton.  I've used them often as
well.  However, my bias remains to activity/usage orientations with the objects largely implicit, since
object modelling can quickly slip into endless invention.  If an attribute or relationship doesn't show
up in an activity, you can forget it.  The world's databases are full of unviewed attributes ,,,

Cheers
Gilbert

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