Taxonomies for Information & Knowledge

Management Architectures

Denise A. D. Bedford, Ph.D.Senior Information Officer - Information Solutions Group Corporate Information Systems

The World Bank Group

Special Libraries Association – DC Chapter – February 4, 2003

Who Needs to Understand Taxonomies?

Anyone who has been charged with the task of organizing information, regardless of the context – Brick & Mortar, KM system, ILS, Portal, Records Management System, …….

You may have been trained to work with a variety of Information Organization tools or trained in bibliographic control principles

It is probably the case that these tools were not presented as taxonomies – perhaps as rules, as record formats…

Professional literature also presents a confusing, often, simplistic view of taxonomies Assumes that a taxonomy is only hierarchical Fails to provide a clear distinction between the structures & uses of

classification schemes, subject headings, thesauri & metadata

Information Management System Architectures

The underlying architecture of a full bibliographic control system, records management system, a metadata repository or corporate information architecture is complex

Taxonomies are essential structures in all information management systems

Information managers, librarians, information architects, knowledge architects, records managers need to be able to:

Understand the different kinds of taxonomies Have sufficient familiarity with their purpose to select the right kind

of taxonomy for an application

Taxonomy Basics

There are four types of taxonomies Flat Hierarchical Faceted Network

Some are explicit/visible, others are implicit/invisible

There are significant design consideration when implementing each different type

Let’s review each quickly

Definition of a Taxonomy

“System for naming and organizing things into groups that share similar characteristics” Jean Graef, Montague Institute

Taxonomy

Architectures Applications

Taxonomy Basics

Four types of taxonomies

Flat

Hierarchical

Faceted

Network

Flat Taxonomy Structure

Energy Environment Education Economics Transport Trade Labor Agriculture

Type 1: Flat Taxonomies

Flat taxonomies group content into a controlled set of categories

no inherent relationship among the categories in a flat taxonomy -- they are co-equal members of a single structure

can move from one category to another without having to think about the relationship between them

concept of a flat taxonomy may be counter intuitive to some

Consider how often you use flat taxonomies everyday

alphabetical listings of people in a directory of expertise a pull-down menu of country names or geographical regions simple alphabetical listings of product groupings

Designing Flat Taxonomies

Flat taxonomies are easy to create

Flat taxonomies do not require complex interface design and extensive usability testing

We have learned from usability engineers how to implement flat taxonomies

Flat taxonomies used for explicit information structures generally should consist of 30 or fewer categories;

More than 30 categories may be presented in a flat taxonomy, if the categories are intuitive to users (i.e. lists of countries, states, languages, etc.);

Explicit Flat Taxonomies

Amazon.com’s pull down list of product categories & horizontal list of stores- http://www.Amazon.com

Nordstom.com’s alphabetical list of brand names - http://www.nordstrom.com

Microsoft PowerPoint’s global functional menu & pull down menu

Water Resources Directory of Expertise list of keywords - http://www.nceas.ucsb.edu/exp/

Bartleby.com’s extensive picklists of reference, verse, fiction & non-fiction listings -- http://www.bartleby.com/

CyberDewey’s alphabetical index to sections - http://www.anthus.com/CyberDewey/Dewey_index.html

Implicit Flat Taxonomies

Alphabetical list of water resource experts

Content inventories listed alphabetically by author

Rights management values (simple picklist)

Information disclosure status values (simple picklist)

Security classification scheme values (simple picklist)

Hierarchical Taxonomy

A hierarchical taxonomy is represented as a tree data structure in a database application. The tree data structure consists of nodes and links. In an RDBMSenvironment, the relationships become associations. In a hierarchical taxonomy, a nodecan have only one parent.

Type 2: Hierarchical Taxonomies Group content into two or more levels

Resemble tree structures when they are fully elaborated

Hierarchical categories typically have only one broader or parent category.

Relationships among categories in hierarchical taxonomies have particular meaning Relationship between a top level category & subcategory may mean

group membership or refinement of the top category by a particular characteristic or feature

Moving up the hierarchy means expanding or broadening the category Moving down the hierarchy means refining or qualifying the category

Explicit Hierarchical Taxonomies

Yahoo’s Web Site Directory - organized as a subject hierarchy - http://www.yahoo.com

Internet Public Library’s two-tier collection structure - http://www.ipl.org

Librarian’s Index to the Internet mixed hierarchy of topics and resource types - http://www.lii.org/

Ebay’s auction categories – http://www.ebay.com

CyberDewey’s progressive disclosure of Dewey Decimal classes - http://www.anthus.com/CyberDewey/CyberDewey.html

Albertson’s Shop By Aisle grocery categories or Shop A to Z grocery product - http://www.albertsons.com/store/categores

Implicit Hierarchical Taxonomies

Electronic news story published in XML NITF format International Press Telecommunications Council. News

Industry Text Format. Version 3.1 September, 2002. http://www.nitf.org/

Classification schemes for topic areas

Authority control lists for abbreviations & full names (aliases)

Records management hierarchical fileroom structures

Cross source topic reference structures

Designing Hierarchical Taxonomies

There is more than one way to implement a hierarchy:

Progressive disclosure of layers across sites or pages -- Ebay model

Cascading or expanding menus -- United Nations web site Pop-up menus linked to stationary menus -- United Nations web

site Category and subcategory labels in a multi-column display --

Nordstrom’s second level pages

Designing Hierarchical Taxonomies

Hierarchical taxonomies should:

have content at every level -- empty categories present empty value to users

be less than four levels deep in most cases

be at least two categories for each branch in the taxonomy -- do not branch for a single category

be sufficient content in each category to warrant existence

balance breadth & depth -- users must work harder to use a taxonomy three categories broad & nine deep than to use one that is seven wide and two deep

Hierarchical Taxonomy Design Issues

Hierarchical taxonomies should:

be balanced across each level of the taxonomy to provide users with a predictable experience

be offset with search functions

should never be displayed into flat structures

be reviewed periodically

Facet Taxonomies

Faceted taxonomy representedas a star data structure. Eachnode in the start structure isliked to the center focus. Any node can be linked to other nodes in other stars. Appears simple, but becomes complex quickly.

Type 3: Faceted Taxonomies

Resemble flat taxonomies when implemented, but have a different structure & purpose than flat taxonomies

There are no inherent relationships among categories in a faceted taxonomy – like a flat taxonomy

Resemble a star structure -- all facets pertain to the center object

All categories in a faceted taxonomy relate to a single object -- may describe a property or a value, different views or aspects of a single topic

Type 3: Faceted Taxonomies

An object may be:

electronic book -- each facet describes some aspect of the book - the author, the title, date of publication

facets describe the country’s population, geography, economic system, political system, history, …

Each facet may relate to facets in other taxonomies -- a faceted taxonomy describing a book may also have a link to a faceted taxonomy that describes a country

Metadata as Faceted TaxonomyThe primary implicit application of faceted taxonomies today & historically is as implicit metadata records

Traditionally, libraries have been the prime users or metadata

Today, portals and e-business systems are primary metadata users

Types of taxonomies that rely on metadata today:

IBM’s product & service catalog on the web

User interest profiles

Knowledge ‘push’ or syndication profiles

Selective dissemination of information or “push” profiles

Standards Based Metadata Schemes

Dublin Core Metadata Element - http://dublincore.org/dcregistry/index.html

GILS - Government Information Locator System - http://www.gils.net

VERS - Victorian Electronic Records Strategy -- http://www.prov.vic.gov.au/vers/welcome.htm

MARC - Machine Readable Cataloging - http://www.loc.gov/marc/marcdocz.html

UDDI - Universal Description, Discovery & Integration of Business – http://www.uddi.org

TEI -- Text Encoding Initiative - http://www.tei-c.org

ISAD(G) - International Standard Archival Description - www.ica.org/biblio/com/cds/isad_g_2e.pdf

Commercial Metadata Schemes

Ebay’s auction item descriptions - http://www.ebay.com

Amazon.com’s product descriptions - http://www.Amazon.com

Albertson’s product descriptions - http://www.albertsons.com/store/

Nordstrom’s product descriptions - http://www.nordstrom.com

Designing Faceted Taxonomies

Most important design issue for faceted taxonomy is that it be suited to its purpose -- that it contain the facets that are needed, & that their behavior is clear

Characteristics of each facet should be defined fully and distinctly -- while all facets pertain to a common object, each has a distinct behavior

Users should be able to manipulate facets distinctly -- it is important to define each facet exclusively, without overlap with other facets

Most faceted taxonomies are implicit structures - when they are made explicit, they are generally presented as record or table formats

Network Taxonomies

A network taxonomy is a plex data structure. Each node can have more than one parent. Any item in a plex structure can be linked to any other item. In plex structures, links can be meaningful & different.

Type 4: Network Taxonomies

Organizes content into both hierarchical and associative categories

May look like a computer network topology

Many relationships among categories or “nodes”

Relationships may have many different meanings

Category may have more than one higher level category

Any category in the taxonomy may be linked to any other category

Type 4: Network Taxonomies

Examples of network taxonomies:

Topic maps or ontologies

Thesauri -- !! A Thesaurus is NOT just a Hierarchy!!

Semantic networks

Implicit cross-walks for thesauri & controlled vocabularies from different knowledge domains

Implicit Network Taxonomies

Thesauri, concept maps & semantic networks can be explicit or implicit

Can be designed transparently into the knowledge management system as:

thesaurus facilitated search systems

recommender engines (...if you liked this, you might also like this)

vocabulary cross-walks from one source system to another

topic map cross-walks from one knowledge domain to another

Explicit Network Taxonomies

At one end of the scale we find simple, explicit network taxonomies such as topical taxonomies with See also references, or fully exposed thesauri

At the other enc of the scale, we find more complex, explicit network taxonomies such as visual concept maps or visual semantic networks. Consider the following example of network taxonomies accessible on the web:

World Bank Group’s Thesaurus – http://www2.multites.com/wb/

UMLS Semantic Network - http://www.nlm.nih.gov/research/umls/META3.HTML

Inxight’s Star Tree concept maps - http://eic.vestforsk.no/sitelense/eic.html

Designing Network Taxonomies

Structure you use to maintain the network taxonomy may not work well for display -- may have to break it into one or more types of taxonomies to implement it

Different kinds of relationships may be implemented in different ways - a single approach to display all types of relationships may not be effective

Three-dimensional presentations are well suited to network taxonomy implemented, but should be usability tested with users

Consider how the user will navigate a three-dimensional presentation

Try to maintain a consistent level of granularity of categories - avoid mixing pre-coordinated subject headings or broad classes with concepts

Conclusions

Every Information Professional’s ‘knowledge toolkit’ should contain a basic understanding of taxonomies & their suitability to different applications

Taxonomies are important building blocks in a full function information architecture

Knowledge of taxonomies will be a skill in increasing demand as the need to organize information grows

Need the organize information is growing exponentially, consistent with the amount of information produced, stored & disseminated