RE: [xml-dev] [OT] Difference between an extensible versus an evolvable information system?

["Bullard, Claude L (Len)" <len.bullard@intergraph.com>]

Title: Message

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

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