Top-down or bottom-up?
david at megginson.com
Thu Jun 17 17:02:32 BST 1999
Len Bullard writes:
> > That's not what I mean -- creating a data model is tractable, but a
> > data model is of questionable value if it's not based on a fairly
> > accurate business model, use cases, etc. I don't think that any of us
> > can reasonably draw up a reliable business model that will cover the
> > Web for the next five years, and even the use cases will be pretty
> > shakey. Without good models, bottom-up is our best bet.
> Umm.. isn't that why we do markup and write DTDs? They may not
> last forever, but like mudbricks that cleave, they make a
> reasonable structure and, well, beat the heck out of fighting bears
> for caves.
Just so, but imagine if we had all waited to start writing DTDs until
ISO approved a master document architecture that would govern all DTDs
in the SGML and XML document space (kudos to HyTime for trying,
This is the point that I (and others) have been making in this
discussion: a top-down approach (start with the master architecture)
can work for something like a new parts-management system for
ACME.com; a bottom-up approach (start with the components, such as
individual specs and DTDs) is pretty much required in an open and
fast-changing system like the Web.
As Paul Prescod has pointed out, however, in both cases the process is
really iterative: in a bottom-up approach, it's often useful to stop
and throw together a straw-man architecture to see if what we've done
so far makes sense together; in a top-down approach, it's often useful
to stop and throw together some proof-of-concept components, to see if
there will be any obvious implementation problems. The difference
comes simply from which of the two is formalized.
All the best,
David Megginson david at megginson.com
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