What are the centers in software?  Are there any?

What Alexander calls a "center" is something that is defined in
terms of other centers.  A center is something that holds your
attention, something that you notice and might name.

A method and a class are probably centers.  A class is made up
of methods, so that fits.  But classes are pretty small.  A pattern
like Composite or Strategy is made up of several classes, and they
are probably centers, too.  A subsystem would be a center, as would
a complete application.  So, there will be centers at many levels,
and larger centers are made up of smaller centers.
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CategoryPattern
CategoryOrganization