Top-down or bottom-up?

Andy Dent dent at
Sat Jun 19 02:01:43 BST 1999

At 11:04 -0400 17/6/99, David Megginson wrote:
>Just so, but imagine if we had all waited to start writing DTDs until
>ISO approved a master document architecture...

>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
>; 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

I was really glad that you included Paul's comment because it reduced 
my blood pressure a few notches.

I regard myself as a software architect and I spend a fair amount of 
my time thinking in terms of the architecture of our software. (This 
is even more important with a tiny team as the proportional cost of 
bad architecture rises in inverse proportion to the size of team - 
big teams can muddle through).

There's been an assumption in a lot of these posts that a documented 
architecture specifies a lot of rigid detail.

I don't see an architecture like that.

The architecture of a design is different from the detailed design. 
The detailed design is the structural specifications and decorative 
work on the columns. The architecture says how many columns fit into 
an aesthetically balanced colonnade :-)

Back in software terms - we are ALWAYS working with an architecture - 
it's the background against which even the most bottom-up of 
developments write their tools. Iterative development is about 
fleshing out an architecture, and sometimes rejecting ideas or 
modifying the architecture to suit, always striving for a balanced 

Andy Dent BSc MACS AACM, Software Designer, A.D. Software, Western Australia
OOFILE - Database, Reports, Graphs, GUI for c++ on Mac, Unix & Windows
PP2MFC - PowerPlant->MFC portability

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