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Ok, but Roger is seeking to distinguish these terms and scientists
are seeking to formulate or preserve a more precise meaning for
evolution. Again, if all evolution means is change, then these
are indistinguishable. If it means the accretion of features
that are inheritable in a population, then it is a different
meaning.
In the case of XML, the evolution is in the application languages.
We can split hairs on XML 1.0 or 1.1, but the evolution there is
in the systems. The language devolved into a simpler state. That's
fine because that enabled it to propagate when the environment
changed. To really understand evolution, one must consider
population and environment. Otherwise, the terms are indistinguishable
from complexity as a measure of fitness.
len
From: Rick Marshall [mailto:rjm@zenucom.com]
> Is XML an evolution of SGML or simply an adaptation (it lost features, so
> maybe it is devolution)?
depends doesn't it - was losing most of our furry/hairy covering
evolution or devolution? sometimes evolution means losing things in a
tradeoff for an overall better position. one of the great lessons of
chess and warfare (although today warfare must progress without loss,
but the debate continues). there is any number of birds that have lost
the ability to fly in exchange for an advantage on the ground or in the
water.
as a counter to the "more categories isn't evolution" you could also
consider the giraffe - is the long neck evolutionary or not.
topographically it's the same as other mammal necks, 7 bones, etc - it's
just very long. evolution or extension ;) ?
i think they're both the same. one way or another the system is changing
to be better in a given situation. it may lose features, gain features,
or change them. it's different because for some reason it needs to be.
rick
>
> len
>
>
> *From:* Roger L. Costello [mailto:costello@mitre.org]
>
> Hi Folks,
>
> I am interested in hearing your thoughts on the differences
> between an information system that is extensible versus an
> information system that is evolvable.
>
> For example, suppose that Amazon.com gives users the ability to do
> a keyword search. Further, suppose that Amazon empowers its users
> to create new keywords (and map the new keywords to information at
> the Web site). Is this support for new keywords an example of
> extensibility or evolution? By adding new keywords has
> Amazon merely been extended, or has it evolved?
>
> Let's take another example. Suppose that Amazon gives users the
> ability to search by book category (e.g., Fiction, Non-Fiction,
> etc.) Further, suppose that Amazon empowers its users to create
> new categories (and map the categories to information at the Web
> site). Is this support for new categories an example of
> extensibility or evolution? By adding new categories has Amazon
> merely been extended, or has it evolved?
>
> If adding new keywords and adding new categories are merely
> examples of extension, then can you give an example
> of evolution? /Roger
>
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