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A-Z Web Site Indexes Explained
Last updated Oct 17, 2003.
(Originally Published December 6, 2004 on Sitepoint.com)
By Heather Hedden
A-Z Indexes are a far more accurate than search engines for searching the content of a web site or intranet. For the value they can bring to a site, A-Z indexes are worth the additional cost, but, if you decide to add an index to your site, it's important to find the right person to do the job.
How Alphabetical Indexes Work
An A-Z Index offers an alphabetical list of "entry point" topics through which the user may browse and select. In an index at the back of a book or manual, the entries are followed by page numbers. On a web site, the entry points are hyperlinked to the appropriate pages, and often to named anchors within Web pages for an even greater level of detail in indexing.
As with book indexes, a site index may contain multiple entries, each worded differently, that point to the same page, or page and anchor. This approach is used to cover all the different ways a user may think a topic is named, and is referred to as "double posting." It covers synonyms, such as "cars" and "automobiles," and the different word order of a phrase, such as "automobile engines" and "engines, automobile." The browsable nature of the index solves the problems that might arise from incorrect or variant spellings, and singular vs. plural usages that the site user might choose.
In addition, there is often a second level of terms, called "sub-entries," that are listed and indented under some of the main entries.
A Web A-Z index is typically a single, long HTML page, although it could be broken into separate pages for each letter of the alphabet if it were extremely long. At the top of the page, a horizontal list of the letters of the alphabet usually appears. (See Figure 1) The user makes a selection from this list, and jumps to the appropriate section of the alphabetical index.
Figure 1 A sample index from a library website
A-Z indexes are created not by machines, but by humans who take care to add index entries only to pages on which good information about the topic appears. In this way, the indexing of topic words mentioned in passing or out of context is avoided, boosting the overall relevance and quality of the index itself.
A list of some examples of A-Z indexes can be found at the web site of the Web Indexing Special Interest Group. The page Web Index Examples has indexes done by SIG members and more examples can be found on the page Other Examples of Indexes on the Web.
Figure 2 Another sample of an alphabetical web site index
Better Than Search Engines
Every now and then, we find an article or other document that says site indexes are a good thing. And every now and then we may come across an A-Z index on a web site, and think, "Hey, that's cool." So, why don't we see more of them? The simplest answer is that the big competitor to A-Z indexes — site search engines — are usually cheaper (or may even be free) to implement. But, in the end, you get what you pay for.
Site search engines may not retrieve enough or any pages.
Whole-Web search engines usually produce "satisfactory" results in the quantity of pages, as users generally want "some information about" a subject, and this can typically be found on some of the numerous pages retrieved. If many good pages are missed by the search engine, the user usually does not notice or care, since enough other good pages are found.
Within a web site, however, the number of pages is relatively small, so a simple search engine search might not yield enough or any results, even if there are good pages on the subject. This is most likely to occur because the search subject the user enters is worded differently than references to that topic within page text.
Site Search Engines May Retrieve Too Many Irrelevant Pages
Whole-Web search engines usually produce "satisfactory" results in the quality of articles, since the major search engine companies have developed complicated criteria and algorithms for the retrieval and ranking of pages. Off-the-shelf search engines to be used within a site are not so sophisticated. They often retrieve pages that include a mere passing mention of the search term, but do not really focus on the subject at all.
Search engines often cannot meet the higher demands that searchers have for searches within a site.
Searchers of a site may want all the information a site has on a given topic, whereas searches of the entire Web only want — and expect — some information on a topic. Searches of a site may also want to find the information more quickly, since they might be looking at a number of sites simultaneously.
In the end, the quality of the search engine results reflects the sophistication of the search string entered by the user, which cannot be controlled. In the A-Z index, on the other hand, the quality of the results reflects the sophistication of the indexer, which can be controlled.
Additional Advantages to A-Z Indexes
In addition to the superior search accuracy, A-Z indexes offer other benefits.
The large number of well-labeled internal links that make up an A-Z index increases the search engine optimization rating of the linked pages and, consequently, that of the entire site.
The absence of irrelevant pages retrieved make the index searching more efficient, enhancing the usability of the web site
The ability to browse the index enables users to digress and explore other topics that catch their attention, keeping them on the site longer. In other words, indexes can enhance the "stickiness" of the site. Finally, A-Z indexes can be effectively implemented on web sites that are too small to work with site search engines, such as sites in the range of 20-50 pages.
No More Costly Than Customized Search Engines
Of course, basic site search engines can be made more effective with tinkering. They can be customized to search only meta tags, and meta tags can then be carefully written for each page. Searches can be restricted to certain pages and/or zones within pages. Results can be tailored to display "key-words-in-context." All this customization requires the expertise of Web developers, whose time is not cheap. And the improvement in the search engine's capabilities can still never match those of a carefully crafted A-Z index.
Creating an A-Z index, on the other hand, is a straightforward editorial task that can be completed by a freelance indexer. Indexers can provide an accurate quote of the job before it begins, based on the average number of words per indexable page or the number of entries in the index. Depending on the size of the web site or intranet, you can expect an A-Z index to cost between $200 and a $1000.
Getting The Right Person For The Job
It's very important that an A-Z index be done well. Although any alphabetical list might look good at first, if users cannot quickly find what they're looking for, they will become frustrated with the index and the site itself. It would probably be better to have no index at all than a poorly created one.
Should you create the index yourself? Creating an index is more complicated than creating a hierarchy of categories or a taxonomy. To become competent at indexing really requires appropriate education. Information architects with backgrounds in library science and a good sense of labeling, however, could probably pick up indexing from reading a good book on the subject. In addition, a tool for automatically embedding the index URLs, such as HTML Indexer, which is my preference, is recommended.
So, where do you find a web site indexer? If you don't want to invest the time and energy in learning indexing yourself, it's probably best to contract a freelance indexer. Most of the professional associations of indexers listed below maintain searchable databases of freelance indexers. Limit your search to HTML or Web indexers. The nice thing about web site indexes is that samples of an indexer's work are usually accessible online, so you can easily evaluate a potential indexer's work.
It's true that manually created A-Z indexes need to be updated when pages are added to or removed from the site, but so do site maps. If a web site is so large and dynamic that it is impractical to maintain a site map, then it would also be impractical to create and maintain an index. For pages that have frequently changing content, such as an announcements page, an index should be written not to the specifics of the content, but merely to the general concept of announcements, so that frequent updates in the index are not needed.
If the index is created by a contracted indexer, an agreement needs to be reached about how the index will be maintained. Either the indexer can be retained for future updates, or the indexer can provide written guidelines to the webmaster on how to maintain the index. For example, after writing an index to a school's web site, I identified the likely additional future pages and wrote up guidelines for the webmaster to indicate the entries/subentries under which the new pages should likely be indexed. In this case, the new pages tended to be individual class pages, each of which would have been best indexed in three places: under the teacher's last name, by grade level, and under the topic "classroom pages."
A-Z indexes will enhance the searchability, usability, and overall quality of a web site with results that are superior to most site search engines. Just because a search engine is free, don't be tempted to keep it on the site once you've added an index. Since they serve the same purpose, the presence of both a search engine and an A-Z index, yielding differing results, would only confuse users and waste their time.
Resources on web site indexing:
Web Indexing Special Interest Group of the American Society of Indexers. Has a searchable database of freelance web site indexers, links to examples of web site indexes, and articles on web site indexing.
Indexing Resources on the Web: WWW Indexing compilation of links by the University of British Columbia School of Library, Archival, and Information Studies
Special Topic Session: Indexing A to Z of the Web Developers Group at Arizona State University
Website Indexing: Enhancing Access to Information within Websites. 2nd edition by Glenda Browne and Jonathan Jermey, Auslib Press, 2004.