Log message for revision 40061:
Expanded motivation.
Changed:
U Sandbox/zc/extrinsicreference/extrinsicreference.txt
-=-
Modified: Sandbox/zc/extrinsicreference/extrinsicreference.txt
===================================================================
--- Sandbox/zc/extrinsicreference/extrinsicreference.txt 2005-11-12 16:30:47 UTC (rev 40060)
+++ Sandbox/zc/extrinsicreference/extrinsicreference.txt 2005-11-12 16:32:40 UTC (rev 40061)
@@ -8,10 +8,27 @@
reference to it's first chapter would be intrinsic. Intrinsic
references are used to satisfy an objects "concerns", the things that
motivated it's design. Extrinsic references exist to meet system
-concerns. We prefer using simple Python references to implement
+concerns. For examples, a system might use extrinsic references to
+keep track of link dependencies (e.g. backlinks).
+We prefer using simple Python references to implement
intrinsic references. This package provides a tool that can be used
to provide extrinsic references.
+We originally developed this package to manage "shortcuts". Shortcuts
+are a bit like windows shortcuts or unix symbolic links. Shortcuts
+hold direct references to their targets. These were intrinsis to
+shortcuts. It wouldn't make sense to have shortcuts without targets.
+We also wanted to keep track of shortcuts to to objects. That is,
+given an object, we wanted to find all of the shortcuts to it. This
+was a system/application choice. We used extrinsic references for
+this.
+
+The above example illustrates that it is often useful to use different
+kinds of references for different directions of an association. We
+often use intrinsic references for one direction and use extrinsic
+references to go the other way. Of course two-way
+associations/relationships could be build on a mechanism like this.
+
Extrinsic registries record a key and one or more values to which they
refer. The key and all values must be adaptable to
zope.app.keyreference.interfaces.IKeyReference.
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Expanded motivation.
Changed:
U Sandbox/zc/extrinsicreference/extrinsicreference.txt
-=-
Modified: Sandbox/zc/extrinsicreference/extrinsicreference.txt
===================================================================
--- Sandbox/zc/extrinsicreference/extrinsicreference.txt 2005-11-12 16:30:47 UTC (rev 40060)
+++ Sandbox/zc/extrinsicreference/extrinsicreference.txt 2005-11-12 16:32:40 UTC (rev 40061)
@@ -8,10 +8,27 @@
reference to it's first chapter would be intrinsic. Intrinsic
references are used to satisfy an objects "concerns", the things that
motivated it's design. Extrinsic references exist to meet system
-concerns. We prefer using simple Python references to implement
+concerns. For examples, a system might use extrinsic references to
+keep track of link dependencies (e.g. backlinks).
+We prefer using simple Python references to implement
intrinsic references. This package provides a tool that can be used
to provide extrinsic references.
+We originally developed this package to manage "shortcuts". Shortcuts
+are a bit like windows shortcuts or unix symbolic links. Shortcuts
+hold direct references to their targets. These were intrinsis to
+shortcuts. It wouldn't make sense to have shortcuts without targets.
+We also wanted to keep track of shortcuts to to objects. That is,
+given an object, we wanted to find all of the shortcuts to it. This
+was a system/application choice. We used extrinsic references for
+this.
+
+The above example illustrates that it is often useful to use different
+kinds of references for different directions of an association. We
+often use intrinsic references for one direction and use extrinsic
+references to go the other way. Of course two-way
+associations/relationships could be build on a mechanism like this.
+
Extrinsic registries record a key and one or more values to which they
refer. The key and all values must be adaptable to
zope.app.keyreference.interfaces.IKeyReference.
_______________________________________________
Zope-CVS maillist - Zope-CVS@zope.org
http://mail.zope.org/mailman/listinfo/zope-cvs
Zope CVS instructions: http://dev.zope.org/CVS