Re: How many use the diagram tree?

["James K. Lowden" <jklowden schemamania org>]

On Fri, 8 Aug 2003 17:25:29 -0400, <ashalper cox net> wrote:
> > > I will desperately need UML views (The Unified Modeling Language
> > > User Guide, p. 468) in the near future.  The diagram is already too
> > > complex to view in its entirety (it is derived from a horrifying
> > > government legacy system).
>
> My interpretation of it is one or more diagrams of the same set of
> objects, each diagram including some subset and only a subset of the
> original set, but otherwise independent of each other.  I haven't used
> Rational or any other commercial UML tool, so I don't know how it's
> implemented there, but ERwin has something similar and I use it quite a
> bit to make less cluttered subschema diagrams of the larger schema.

A simple ER diagram has a dozen tables and is no problem to navigate.  A
complex one has >100 tables and presents many, um, presentation problems. 


Two very useful features: named subsets, and diagram view settings.  

Named subsets are user-defined collections of objects that have their own
diagram space.  When you view a named subset, you can arrange the objects
as you like without affecting the main diagram.  This lets you create a
sub-diagram for the "customer" tables, say, as distinct from the "product"
tables.  Very useful for meetings, if nothing else.  Any changes to the
objects' attributes are of course reflected in the main diagram, because
there's only one copy of the object's attributes.  A given object may
appear in N named subsets, and have an independent location in each one. 
"Tabbed diagrams" would seem to me to be the natural way to present named
subsets to the UI, FWIW.  

Diagram views are an orthogonal concept.  What order do you want to see
your table's attributes in?  Physical, or key-first?  What information do
you want represented about the attributes?  Their datatypes, nullness, key
participation?   

As long as I'm just naming random features, let me add one that sounds a
little bizarre but turns out to be quite handy.  Right-click on a line,
and the menu says "go to parent" and "go to child" (among others things). 
Pick one, and -- zip! -- there you are.  

--jkl