TITLE: DejaNews

ACCESS: http://www.dejanews.com
Its URL is:http://www.dejanews.com
It is also listed on the Netscape "Net Search" page.

DejaNews Research Service is a general-purpose Usenet search tool. Because DejaNews indexes most Usenet news groups, it can be used for searching on a variety of topics. Its intended audience is the general user seeking current information.

According to documentation screens, the alt, talk, and soc hierarchies, as well as all .binaries groups, are specifically excluded. Ostensibly this is done to focus the search on those groups likely to contain actual information, but it can have the effect of removing from the search those groups in the alt hierarchy where the newest technologies are discussed (before there was a comp.infosystems.wais, there was an alt.wais). In fact, searches do retrieve results from talk.politics, soc.culture, and other "excluded" sub-hierarchies, so the limits of the coverage are actually rather vague.

Currently the site indexes several months' postings, evidently since its start date in early 1995. The plan is to keep a rolling year of postings in each newsgroup once a year's news has accumulated.

DejaNews requires a forms-capable World Wide Web browser. It supports searching by subject and by author, but defaults to free text keyword searching of the body of each message.

Several screens of documentation are available. Reading them is recommended, since a simple default search is likely to retrieve a large number of very miscellaneous postings. Unfortunately, a more complex search using wildcards, parentheses, and Boolean or proximity operators can result in an error message for no apparent reason. These messages are generally cryptic, although the screen announcing zero retrievals is undeniably unique.

The option of narrowing a search by Usenet group or hierarchy is a useful feature, although it does not work exactly as expected: limiting to the newsgroup rec.pets.cats actually retrieved postings from rec.pets as well. There is no list of available newsgroups to select; the user must enter the group or hierarchy name.

Because the relevance ranking scheme in DejaNews does not give extra weight to words appearing in specific contexts, such as in message subjects or in keywords assigned by the person posting the message, irrelevant postings are readily retrieved based on words that happen to appear in a signature at the end of a message. The only way to "weight" message subjects is to specify a subject-field search explicitly. In effect, the user must choose either precision or recall. A fairly complex search statement can approximate a combination of the two, but an adjustment to the weighting scheme would accomplish this much more effectively.

Some fields in retrieved messages can be clicked on for more information about the author or related messages in the same "thread." The latter did not seem to be working properly: instead of following the thread in a newsgroup, it retrieved messages from a variety of newsgroups.

With some practice, I was able to use the DejaNews service to retrieve a specific newsgroup's FAQ and to retrieve postings similar to the results described in the DejaNews tutorial. However, as a general-purpose information lookup tool, DejaNews is of only incidental value. It is only a search mechanism; the content it searches is provided by those who post messages to Usenet, who are under no obligation to provide accurate information over personal opinion, or even to cover a particular topic at all.

Some newsgroups do contain a great deal of accurate information content, and where this is the case, the most concise source of information is the FAQ (frequently asked questions) file. These can be located via DejaNews, but they are also available in the Usenet FAQ repository at ftp://rtfm.mit.edu.

Where Usenet news shines is in its coverage of actual "news," that is, job listings, apartment sublets, and other announcements; reports, including

opinions, from regions where news is occurring, or from which little published news or information is available; and so on. DejaNews could be used to search for these, although it should be weighed against other resources such as collections of Usenet postings at subject-specific sites. For example, students seeking career leads are likely to find more relevant material at a site such as CareerMosaic (http://www.careermosaic.com), which carries both Usenet and other information related to job seeking, than with a DejaNews search alone.

Where DejaNews shines is in its ability to retrieve results from a variety of newsgroups and in its author search. When Usenet is an appropriate resource for answering a question, but the specific newsgroup containing the answer is uncertain, DejaNews makes it possible to find out whether the answer is there. This can be particularly useful where accurate information is not at issue, e.g., when what is sought is an opinion. Searching for the opinions of, or quotes from, a known individual is facilitated by the DejaNews author search.

An interesting side effect of the author search is that, at least across the universe of those who post messages to most of the Usenet hierarchies, DejaNews can be used as a tool for looking up e-mail addresses. Although false drops are to be expected, and although those who post no Usenet news are automatically excluded, e-mail addresses can be so tricky to locate that this is a handy feature.

Genevieve Engel
University of California

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