RE: Broad and flat vs hierarchical facets - beginning with introducing myself

Bill,
 
I am a strange kid here on the block since I know little about library
science nor am I strong in IT. My trade is human factors, cognitive
psychology, usability. So my answers are somewhat different.
 
You wrote:
1. What is the practical maximum number of items that can be included in
a flat (alpha or logically sorted) picklist before users won't use it or
can't find the item they are looking for?

Marcel:
There is the 7 plus or minus 2 rule. This rule means that if the items
have nothing to do with each other, you should never have more than 9
items and optimally only 7. In reality, don't go over 20. This number
can increase if there are logical relations between the items.
 
You wrote:
2. In a hierarchical picklist, how many layers are considered to be
practical and what is the practical maximum number of items that should
be presented in a layer (assuming that the hierarchical logic allows
much freedom to go flat vs deep)? 

Marcel:
Hierarchies are fine when people perceive the data as a hierarchy.
Geography is a good example. I consider Amsterdam to be part of the
Netherlands and I think the Netherlands is part of Europe. In principle
there is no limit to the layers whenever the hierarchy is clearly there
(according to your users)
 
You wrote:
Other experience-based comments based on working with systems like I
have described would be welcome.

Marcel:
Assumption: Adding metadata to information must improve information
retrieval. Because of this asssumption, metadata need to meet certain
quality. 
 
A lot of metadata, like most of the Dublin Core data, do not improve
information retrieval. They simply add associations to information that
help people who know about this information, to find it back. This is a
good technique to create some structure in your own information so you
will not always look at more than a 1000 items. But it does not support
information retrieval. The date, the author, the ISBN-number, all these
things do not reveal anything about the information. They only support
people who have associations with the information.
 
The user I am trying to support has no clue whether the information
exists. I communicate through metadata when my information is relevant.
This type of metadata need to meet the following criterea:
 
1. The metadata describe both the subject (topic) and the user scenario
(user, goal and condition) in which the information is relevant. Experts
will mostly need the subject, novices will depend more on the user
scenario for retrieving information. Metadata reveal what the
information is about and what the information enables me to do.
2. The metadata really show the message (the intention) of the
information. When I find information under "legal department" the
information must explain something about the "legal department". "Legal
department" should not be just another place for hiding your
information.
3. The metadata must be clear. The book "Women, fire and dangerous
things" explains this very well. It says that there is an optimal
abstraction level. "car" is clear, "vehicle" is less clear. Use
extremely clear metadata because you will communicate in just a couple
of words
4. The metadata will only point to useful information. Sometimes I see
people who have the goal to classify all information. This will decrease
their metadata to the level of search engines. Metadata must only point
to useful information. Leave the information out of your classification
if it is hard to describe the purpose of the information. The only
reason why we have the Open Directory Project is because there people
out there that can tell us where the useful information is, not all the
information.
 
These criterea should be tested in a usability test, giving the user a
real life task to find certain information and see whether the metadata
will help and do not prevent this person from finding the necessary
information.
 
Marcel
 


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