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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: [OT] Difference between an extensible versus an evolvable
 If you
define evolution as the accretion of new features, sure. If you mean
adding new
instances of those features, no. In any layered system, one must be
careful to specify
which
layer is evolving vs one that is merely accreting.
If you
define evolution as 'change' one *might* say this is evolution. Amazon
added categories
so the
addition of the categorical function is evolution (a new feature) but adding
categories
is
extensibility.
In a
biological system, evolution is a feature that is inheritable. Comparing
that to Amazon,
those
are not evolution unless adding categories or search to Amazon adds it to any
descendant of Amazon or any system derived from Amazon. If
Amazon cannot have
decendants, it cannot evolve. In this sense, evolution is an
observable process of
populations as they adapt to their environment, shape their environment,
and then
adapt
to those changes (mediated feedback). So my question to you
is, what
is the
equivalent of Amazon.com genes? Adding categories could mean the
information is evolving, but Amazon evolved only when the categorical
function
was
added, and then it accretes categories.
My position would be that XML evolution is in the addition or
deletion of features
of a
schema (at any metalevel one cares to work) because it defines the system.
So one
might look at how instances acquire new elements and attributes that are
then
added to their schemas as definitions. For example,
aggregation: why would
one
relax constraints such that composite documents become
homogenous?
One
might do that if working on one product in isolation and fits HTML elements into
say
SVG applications.
Is XML
an evolution of SGML or simply an adaptation (it lost features, so
maybe
it is devolution)?
len
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