Question: Individual annotations vs One large annotation (conceptual riddle for the interested)

[Georg C. F. Greve]

Hi Bernhard,

There are use cases where XML objects are clearly the better approach, there 
are also cases where they are vastly inferior. Typical examples are:

 * Anything for email folders:

	This will result in a mix of object types within email folders that will
 	raise the complexity for clients displaying the folders as they can no
 	longer rely upon the folder type, and non-Kolab clients will more easily
 	break the configuration.

	The alternative results in the next point, and a good chance for data
	rot as now the meta data for one particular folder is no longer stored
	in that folder.

 * More complexity

	Where a per folder setting can easily be stored in a shared/private 
	namespace, and conflict resolution between different settings is easy,
	doing the same through XML is more complex.

 * Vastly inferior performance

	Clients always need to parse everything to retrieve a single setting,
	likely across all folders, parsing each object, including filtering
 	through hundreds of thousands of email messages to make sure
	no configuration object is stored among them.

	This is in the area of infinitely worse performance in comparison to
	annotations, which are a well understood and established mechanism
	by now and supported by virtually all the IMAP servers we care about.

That said: There are clearly cases where XML objects are preferable.

In my view, the dividing line runs between transient and permanent 
information. Permanent information is everything that is potentially stored 
forever, so email, groupware objects, and user specific data, such as a 
personal dictionary, even colour sets for commonly used categories across all 
object types and the entire data tree.

Transient information is pure configuration data that loses its value with 
folders or objects disappearing, so often folder or object specific settings 
and meta data, e.g. folder colours, object specific caching or searching 
information, even the folder type.

Another deciding bit can be the need to search for information quickly on the 
IMAP server without a full cache of everything, but this would have to be a 
very strong case to break the logic above, IMHO.

That said: It would have been helpful to get your input on the actual question 
discussed in this thread.

Best regards,
Georg


-- 
Georg C. F. Greve
Chief Executive Officer

Kolab Systems AG
Zürich, Switzerland

e: greve at kolabsys.com
t: +41 78 904 43 33
w: http://kolabsys.com

pgp: 86574ACA Georg C. F. Greve
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