A Modern Librarian's Guide to Hierarchical Taxonomies

Hierarchical taxonomies are an essential tool for modern librarians. This taxonomy structure arranges information into hierarchies, with broader terms at the top and more specific terms at the bottom. By mastering the use of hierarchical taxonomies, librarians can easily organise, index and aid retrieval, helping users to retrieve information resources faster and more efficiently. In this blog post, we will explore the fundamentals of hierarchical taxonomies and the best practices for modern librarians to use in their daily work.

What is a hierarchical taxonomy?

A hierarchical taxonomy is an organised system of categories, labels, and descriptors that allow for the efficient indexing of content in a library collection. They are also known as hierarchical indexing, preferred vocabularies, or controlled vocabularies. Hierarchical taxonomies are used to create a structure for storing and retrieving data by assigning meta-data descriptors to items. This helps users navigate and find information in your collection more quickly. The terms in the hierarchical taxonomy are arranged hierarchically, meaning they form a multi-layered structure with a top-level parent term and child terms beneath them. The hierarchy allows each term to be classified further, making it easier to search and retrieve specific content.

When you are indexing your collection, each time you add index terms to a catalogue record, you must follow some ground rules about which terms to use and how those terms relate to other terms. Taxonomies are called controlled vocabularies because the library indexer must choose terms to describe the item from the hierarchy and there is only one preferred term to describe each concept.

A legal taxonomy may start with legal jurisdictions, which contain broad areas of law, which then have child terms for specific legal concepts, e.g., English Law>Company Law>Shareholders>Minority Shareholders. A school library will need a taxonomy with the broad curriculum topics at the top of the list: Science, History, Mathematics, Fiction, etc. and then the different subjects within each topic, e.g., Science>Physics>Gravity.

Indexing is aligned with but not to be confused with the act of classification because classification is about the organisation of information in a collection usually in a subject area, while indexing is about providing multiple ways of finding the item no matter which classification number it has. Classification aids browsing on the shelves, while indexing is an aid to searching the catalogue. For example, a book about growing and using herbs could be classified as Horticulture, Beauty or Cooking. The librarian can only choose one classification number for its place on the shelf depending on the emphasis of the collection, and then add multiple terms from the hierarchical taxonomy for searching including herbs, perennials, gardening, aromatherapy, and cooking so users can easily find it.

How do hierarchical taxonomies help library users?

As we established above, hierarchical taxonomies provide a means of consistently describing library resources which helps both librarians and users. By creating a hierarchical indexing system, it is possible to quickly find and access the information needed at any level. Librarians can use controlled vocabularies, preferred vocabularies, and external ontologies to improve the precision of the discovery process. Imagine the length of time it would take if, without a controlled vocabulary, users would have to think of all the possible synonyms for describing items to feel confident that they had found all items!

Essentially, it provides library users with a well-structured method for browsing and retrieving items efficiently. Overall, hierarchical taxonomies are essential for modern librarians and help to ensure that library users have an effective and positive experience when using the library’s resources.

Advantages and disadvantages of hierarchical taxonomies

By having a highly organised and structured taxonomy, librarians can confidently add meta-data descriptors to each item in the collection knowing that this will also help library users in their discovery. Sometimes users don’t know what they want and so might start with a broad search on “Company Law”. From these results, a good library system should have features to help the user discover what’s available by offering filters of the more specific terms and the additional terms assigned by the librarian. When a user is looking for specific information like a book on “minority shareholders”, they can easily find this term in the taxonomy and straight away review all items indexed with that term.

Moreover, a library management system that provides hierarchical taxonomy functionality can save the time of librarians by automatically adding the higher terms when the librarian selects terms at the most specific level. For example, if you add the term “Gravity”, then the higher terms “Physics” and “Science” would also be added. This would not be possible with a flat or non-hierarchical taxonomy because there would be no layers or relationships between terms.

However, there are some disadvantages to using hierarchical taxonomies as well. The main downside is that it can be difficult to create a hierarchy that properly reflects all the information within a collection. Additionally, maintaining and updating a hierarchical taxonomy can be time-consuming, requiring extra attention to ensure that everything is correctly structured. Rather than creating your own, you can consider using a published taxonomy suitable for your subject discipline. You can either use one unaltered or, if required, you can revise it to reflect your specialist collection by expanding some sections.

Overall, hierarchical taxonomies are a great way to index library collections, but they should be carefully designed and implemented to ensure accuracy and efficiency.

Why you might need multiple hierarchical taxonomies

The most widespread use of hierarchical taxonomies in libraries is for subject terms, but they can be useful where you need a controlled and structured set of meta-data descriptors for other purposes. For example, you may wish to create a separate taxonomy for Academic Departments, Work Teams, or Practice Groups in your organisation so you can index items that are useful or relevant to people in those groups. In a professional library, you may wish to create other taxonomies for Types of Work, Legal Entities, Industries, Regions, Places, etc.

The advantage of doing this is to provide the user with multiple ways of accessing the information resources and filtering very quickly to get to the precise resource needed for their task. So if a student needs titles for their course they can find them very quickly. If a lawyer needs a Conveyancing Contract for the Aircraft industry acting for the Seller they can find that quickly without having to browse through hundreds of items under Contract Law.

Summary

At the end of the day, hierarchical taxonomies ensure consistent retrieval of items indexed by a single descriptor, while multiple hierarchical taxonomies take searching and discovery to a more advanced level. Multiple hierarchical taxonomies make space for unforeseen and multi-dimensional searches to meet specific information requirements of the user, saving them time and giving them confidence that they can find the things they need. Before you choose a library system stop and think if you need functionality for single or multi-hierarchical taxonomies, but at the very least make sure the taxonomy is hierarchical and not simply flat for all but the smallest of library collections.

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