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May 2009

Looking Ahead to Faceted Searching - Part 2

May 20, 2009 | Alan H. | Comments (9)

In the last post we discussed the history of library search technology as a lead-up to our forthcoming addition of faceted search to the library catalogue. 

But we didn't say all that much about what faceted search is.  So what is faceted searching and why is it exciting for improving the library catalogue?

Faceted Search Defined

A search of the web will turn up quite a few results for the question "what is faceted search?"; I like the definition offered by the Association for Computing Machinery's Special Interest Group on Information Retrieval (SIGIR does a lot of work in areas of computer technology of specific interest to libraries):

The web search world, since its very beginning, has offered two paradigms:
  • Navigational search uses a hierarchy structure (taxonomy) to enable users to browse the information space by iteratively narrowing the scope of their quest in a predetermined order, as exemplified by Yahoo! Directory, DMOZ, etc.
  • Direct search allows users to simply write their queries as a bag of words in a text box. This approach has been made enormously popular by Web search engines, such as Google and Yahoo! Search.
Over the last few years, the direct search paradigm has gained dominance and the navigational approach became less and less popular. Recently a new approach has emerged, combining both paradigms, namely the faceted search approach. Faceted search enables users to navigate a multi-dimensional information space by combining text search with a progressive narrowing of choices in each dimension.

From a 2006 SIGIR conference on faceted search

An Old Idea in the Library World

Faceted search as an idea is related to (though not identical with) the concept of faceted classification, a fairly old idea in the library world.  See the Bliss Classification System or the Colon Classification System, both developed by librarians who considered the Dewey Decimal Classification System insufficient for describing and categorizing the richly varied world of information.

"Navigate a multi-dimensional information space"

A piece of information (let's say a book from here on out for the sake of convenience) has many different possible points of access that might be of interest to someone looking for it.  This is where the "facets" terminology comes from--each possible access point is one "facet" of the whole piece of information.

Some of these are "flat", such as the name of an author or the title of a book, but for others it may be possible to identify a hierarchy from general to specific, such as for geographic area of coverage:

  • Earth > North America > Canada > Ontario > Toronto

A huge range of possible books exist within the geographic coverage of "Earth".  A narrower subset of that range geographically covers "North America", and a narrower subset within that covers "Canada".   And so on... You could also consider more granular hierarchies such as having "Western Hemisphere" between "Earth" and "North American Continent".

But hierarchical subject browsing based on a subject heading system such as the Library of Congress' has been a feature of some online library catalogues in the past.  The real power of faceted searching comes with...

"Combining text search with a progressive narrowing of choices in each dimension"

You may already use faceted search and not realize it.  The ability to start with a free-text search and then narrow down your results within various dimensions is a common one on e-commerce sites:

Canadiantire Ebay

The screenshot to the right show the websites of Canadian Tire and eBay using faceted search to narrow within a free-text search.

You get a lot of power from this ability to search freely and then progressively narrow your search by the available facets of the retrieved results.  Ideally you get the best of both worlds in a user-friendly manner--you can look for whatever you want, but the system will then progressively guide you through its particular information structure to improve precision, eliminate false hits, and help you find information that's on target.

If you've asked a librarian to look up a book (we have 99 branches to do this at if you feel the need) you've probably seen them pull relevant results very quickly, because librarians have extensive training in (among other things) the particular way in which catalogue records are organized.

A big part of what the web team hopes to do with faceted search is leverage our existing structured records (subject headings and other access points in the catalogue record) to make searching easier without having pre-existing knowledge of how the information is organized##.

Faceted Search Technology and the Library

For an example of faceted search working in a library catalogue, you can visit the North Carolina State University Library.

The specific faceted search technology we'll be using is made by Endeca.  An interview with one of the founders in 2008 gives some insights into the origins of the technology (and it warms my librarian heart to see the acknowledgement of S.R. Ranganathan as one of the original thinkers of faceted search).

The web team aims to have faceted search technology in place for Toronto Public Library by late summer.  Watch this space for further announcements.

Looking Ahead to Faceted Searching - Part 1

May 7, 2009 | Alan H. | Comments (17)

The web team's work at Toronto Public Library is a combination of day-to-day maintenance (keeping our existing web and interactive services working and their content updated) and longer-range projects to improve, revise or replace existing services and resources, or introduce completely new ones. 

A major current project is the introduction of faceted search capabilities for the website and the library catalogue as part of the larger redesign of our website.  To understand what this is and why it's a major thing for us we have to talk a little about the history of search, especially as it relates to libraries.

Pre-Electronic Search In Libraries

Before computerized catalogues the primary means of access to books was the card catalogue:

Sample card catalogue image

{made with the Catalog Card Generator}

Some of you may remember using card catalogues (perhaps even fondly).  I can't claim total accuracy in the one above because I barely remember using them.  They took up a tremendous amount of space to hold all those cards and were difficult to keep in good order!  Many of the cards were cross-references to other cards to let you know things like:

  • The correct spelling in the catalogue of an author's name, if there were variants
  • The correct title of a book with variant titles
  • The correct subject heading in the controlled vocabulary used to make sure synonyms and related terms (dog, canine, hound, puppy) were grouped together, usually the Library of Congress Subject Headings

Card catalogues relied on highly structured systems for organizing information that required a certain degree of expertise and experience to use.  A major role of the librarian was to assist in the use of the catalogue to help you locate the book you wanted, as well as maintain it. 

Because card catalogues took up so much space, they had very few access points by which you could search for information.  Typically you had:

  • AUTHOR cards, to let you find out which books the library had by a particular author
  • SUBJECT cards, to locate books on a particular subject--as mentioned above, the synonym problem required the use of controlled vocabulary
  • TITLE cards, to locate books by title

The Card Catalogue Goes Online

This glosses over an enormous amount of library history, but take a look at this screenshot from our current library catalogue:
Notice anything familiar?  Those same card catalogue access points are still there! 

Partly this is because they're good access points.  Most people looking for a book (or a film, or a CD, or another kind of recorded information) are looking for it by one of three broadly defined things:

  • Who made it? (author)
  • What's it called? (title)
  • What's it about? (subject)

Past and Future of Library Searching

Libraries have been doing search technology for a very long time (long before computerized search systems even became possible), and to really understand why the modern-day library catalogue is the way it is, you have to understand some of that history.  The pre-amalgamation North York Public Library began doing computerized cataloguing in 1982, quite a few years before the World Wide Web even came into existence, and the earliest forms of computerized information storage for libraries basically just replicated the card catalogue in computer form (and in many cases were used only by the staff to maintain the catalogue and print new cards as needed, not by the public).

Our existing catalogue records still have a lot of value--it's hard to beat a library catalogue for precision searching, but they're not always very easy to use.  How do we make use of that precision in our records while increasing usability for our public?

As you've probably guessed one answer is faceted searching:


{Screen of the North Carolina State University Library catalogue, using faceted search}

In the next post we'll talk about what faceted searching is and how we envision it working at Toronto Public Library to improve the catalogue experience.

Ask A Librarian Beta Links on the Catalogue

May 5, 2009 | TPL Staff | Comments (11)

Toronto Public Library is always looking for ways to make it easier for you to get the help you need.

Starting May 5th, for two weeks, you will see a new set of links on the catalogue aimed at providing you quick access to help where you need it.

Why don't you see the links every time you visit the catalogue?

To help us make sure we can meet demand we elected to test this with a small set of customers.  As a result you will see the links on some visits to the catalogue and not on others during the two week period. We hope to make the links permanent very soon for all your catalogue visits.

Ask A Librarian Beta Links

Staff from the Toronto Public Library's eServices team talk about recent changes, future plans and ideas and issues you raise about the library's online and mobile services.

What the Web Team is reading on the web