Advanced Search - Page 24
June 8, 2001
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Global Search
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The default for a search engine should be to search the
entire site. Users don't necessarily realize what part of the
site they are currently on, so if the search defaults to only
searching the current subsite, they may think that they have
searched the entire site or even that they have searched a
different subsite.
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Boolean search should be avoided because all experience shows
that users cannot use it correctly. We have studied many groups
of users who have been given tasks like this:
You have the following pets:
Find information about your pets.
Almost all users will enter the following query:
cats AND dogs
In our studies, users typically do not find anything with this
query, because our test site does not include any pages that
mention both animals. Upon encountering a "no hits found"
message, the vast majority of users conclude that there is no
information available about these pets. Even experienced
programmers will normally use the erroneous query. The main
difference is that when the geeks get the null result, they
typically say, "Oh, yes, I should have used an OR instead of the
AND."
Unfortunately, most users have not been taught debugging, so they
are very poor at query reformulation. This is why I recommend
minimal use of scoped search and no use of Boolean search in the
primary search interface. Advanced search is fine if offered on a
page different from the simple search. The advanced search page
can provide a variety of fancy options, including Boolean,
scopes, and various parametric searches (e.g., only find pages
added or changed after a certain date). It is important to use an
intimidating name like "advanced search" to scare off novice
users from getting into the page and hurting themselves. Search
is one of the few cases where I do recommend shaping the user's
behavior by intimidation.
In general, computers are good at looking at long lists of stuff
and remembering whether any alternative words exist that should
be searched for. Users are notoriously bad at this exact same
task, so it is pretty clear what a well-designed search system
should do. The system should perform spelling checks (both for
user queries and for document terms), and it should offer synonym
expansion.
AnswerBook2 web-based documentation interface uses scoped search:
Each user can set up a so-called personal library with a list of
those parts of the large information space that normally is of
interest to them. By default, the search uses this personal
library as the search scope. In this example, only one, and not
very promising, hit was found for the user's search.
Below the list of search hits are suggestions for how to improve
the search. We tried many different placements for these
instructions, and the one just below the search hits proved to be
the best. When users get to this part of the page, they're
motivated to read about ways to improve their search. Without the
instructions, many users overlooked the option to search the
complete library and so never found any information that was not
within their initial search scope.
To get this page, the AnswerBook2 user has repeated the search,
but this time with the search scope set to the complete library.
Many more hits were found, including many good ones in the System
Administrator collection. Apparently, the problem the user wanted
to read about (installing printers) was considered a system
administration task by the designers of the documentation.
Because the set of online documentation is a structured
information space, the search results list can present the search
hits in context, which makes it obvious to the user that most of
the promising hits are in the System Administrator collection.
The use of book icons (and indeed the very name of the online
documentation) indicates a book metaphor that is emphasized by
terms such as "personal library." In general, book metaphors are
probably not the best for hypertext, but it is a good match for
this particular information space, which is highly structured
with all information about a certain domain made into a "book."
Barnes & Noble's search engine conducts a spelling check on the
user's query terms when it doesn't find any matches. In this
case, the user could misspell my name (which is done very
frequently) and still find my books. As an interesting aside,
note that this spelling correction also handles cases where the
user spelled the name correctly but the site had a spelling error
in its database.
Search Capabilities - Page 23
Designing Web Usability
The Search Results Page - Page 25
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