Boxes And Arrows : The Design Behind the Design

All About Facets & Controlled Vocabularies

by Fred Leise and  Karl Fast and  Mike Steckel on 2002/12/09 | [17 Comments]

This is the first in a series of articles that aims to correct this situation. We intend to explain both facets and the more general concept of controlled vocabularies. We want to make the subject accessible to those who don’t have advanced degrees in library and information science. Furthermore, we want to show how these concepts can be applied to solve information architecture problems for the Web and other digital information environments.

The concept of faceted classification is decades old, and controlled vocabularies go back even further. Consequently a great deal has already been written about the subject. But these writings are not always helpful to the practicing IA. Some are too simple, others too academic. Most are hard to find, and many were written decades before this Web thing happened.

• Practical. We will give you a practical guide to controlled vocabularies and faceted classification. We will not only explain the concepts, we will show you how to apply them in solving real information architecture problems.
• Readable. Too much of the existing literature is hard to understand. It may be comprehensible to someone with a master’s in library and information science, but this excludes a large number of practicing IAs (and we know some librarians who don’t understand this stuff). We will use plain talk to explain this stuff, without dumbing it down.
• Relevant. We will make this relevant to the Web and other digital information environments. A great deal was written about this topic in the 1950s and 60s. It’s excellent material, but back then transistors were still a pretty neat idea. We believe that faceted classification has even more applications today than it did back then.
• Accessible. Everything will be published here on Boxes & Arrows: on the web, easy to access, and free. While a lot has been written on this topic, it’s often hard to obtain. For example, B.C. Vickery’s excellent book, “Faceted Classification: A Guide to the Construction and use of Special Schemes” was written in 1960 and is rather difficult to obtain today (at least one of the authors has resorted to finding a copy in a library and, in desperation, photocopying the whole thing).

The plan
Our main goal is to explain faceted classification. However, a faceted classification scheme is actually a special case of what are called controlled vocabularies. To properly explain facets we will begin with this more general topic and work our way up to facets.

• Controlled Vocabularies. In the first full article in the series we’ll describe controlled vocabularies in general. We’ll talk about what they are and how they work.
• Synonym Rings & Authority Files. Before moving on to facets, we’ll describe these simpler types forms of controlled vocabularies. There are many situations where they are more useful solutions because they’re easier to create, implement, and maintain. Sometimes they’re not enough and it’s time to step up to facets.
• Facets & Facet Analysis. With the fundamentals in place we will move on to the heart of our subject. This will take a while, but it’ll be worth it. We’ll also take time to describe facet analysis, the process used to develop facets.
• Interface Issues. A long-standing weak point of controlled vocabularies is how to use them effectively in an interface. This is particularly true of facets. We’ll explore these issues and give you the best advice we can.
• Decision Factors. Not every project calls for a full blown faceted solution. Sometimes a synonym ring is better. How do you know? We’ll cover some guidelines for making those decisions.
• Future Directions. There are some interesting new applications related to facets and controlled vocabularies such as XFML (http://www.xfml.org/) and Topic Maps (http://www.topicmaps.org/). We hope to cover these as well.

We view this as a collaborative effort. We anticipate many questions. We’ll answer these through the discussion features of Boxes & Arrows. We also plan to address the bigger questions you have in subsequent columns. Let us know what you want to know, and we’ll do our best to provide you with answers.