# HG changeset patch
# User paulb@localhost.localdomain
# Date 1185666704 -7200
# Node ID 41d635a383c7129b2a878e85f501ebbaea76db7c
# Parent  589fc634882e354da12861af36d3d2abe6fc8bec
Added notes about classes and instances.


diff -r 589fc634882e -r 41d635a383c7 docs/architecture.txt
--- a/docs/architecture.txt	Sat Jul 28 21:08:44 2007 +0200
+++ b/docs/architecture.txt	Sun Jul 29 01:51:44 2007 +0200
@@ -76,6 +76,28 @@
 
 [1] http://java.sun.com/docs/white/delegates.html
 
+Classes, Attributes and Instantiation Behaviours
+------------------------------------------------
+
+A superficial view of the relationship between classes and instances in Python
+is that instances of a particular class can mostly be treated as equivalent -
+the class defines the behaviour of them all, and the kind of data stored (or
+rather referenced by each of them) is likely to be mostly identical. However,
+we know that some classes encourage a more heterogeneous usage of their
+instances: lists, for example, often contain a variety of different kinds of
+data, and it is often accurate to note that within a given program the
+contents of list objects may vary substantially. Consequently, whilst a simple
+view of instances and their equivalence may hold for some classes, others
+require a more sophisticated view of instances created from them.
+
+The simplest class behaviour states that only one kind of instance exists for
+each class; a more sophisticated behaviour states that potentially many kinds
+of instances exist for a class. In a running program, all instances are
+distinct and there may be no limit (other than that of physical resources and
+of time) to how many there may be in the lifetime of a program. However, when
+modelling the behaviour of a program, it is necessary to be more conservative
+when attempting to identify such instance types.
+
 Instance Filtering
 ==================