Here is a demo that I did with my library team this week. Here is a set of objects:
The challenge was to sort them into groups and explain why you have chosen to arrange them in this way.
We came up with a variety of ways in which they could be arranged – here are some examples.
Grouped by colour:
Grouped by width: one stud, two studs, more:
Grouped by depth: are they flat or built-up?
All of these answers are valid, as they are supported by rational criteria for grouping the objects.
However, notice that as you group items by one characteristic, you separate them by another, e.g. the brown group has some pieces that are flat, but not all the flat pieces are brown.
In a library example, you could put all fiction books together, but an author may have also written drama or poetry, and so not all of their works will be together. Similarly, grouping books by year of publication separates them by subject.
Ranganathan’s Fourth Law of Library Science is “save the time of the reader”. In order to meet the needs of library users effectively, each library must decide how it will arrange its stock: which classification system to use. The best way to arrange your stock is the way in which your users can most easily find what they are looking for.
For example, my library uses the Dewey Decimal Classification system to arrange books by subject. This is the most helpful for our readers, who are usually studying one subject and expect all of their resources to be located in one place.
In a closed stack library, users request books from the catalogue which are fetched for them by library staff. A closed stack library may arrange their stock in order of accession number, meaning that items are arranged from oldest to newest, and this makes efficient use of space. It doesn’t matter that the books aren’t in order by subject; as the library staff member can locate the book accurately by its accession number.
A fiction library may arrange works by author, and a picture book library by colour. At home, my non-fiction books are arranged in height order, as this is aesthetically pleasing and encourages serendipitous rediscovery of other things when I am looking for something else.
As in the examples above, when you group items by one characteristic, it is inevitable that you will separate them by another. However, the most important thing is to choose a system that will help your users, and apply it consistently.