As the size of organizations has increased and electronic communications have become more widely used, maintaining printed versions of information has become impossible. The sheer volume of change between when something is printed and when it is actually used renders the printed form of a phone book, for example, frus- trating to use and even harder to maintain.
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Phone books represent another important type of directory: a directory that is used as a lookup service. Phone books contain information that is used to contact someone or something else. The form of phone book that we work with every day is still a printed version—the phone book that lists people and businesses in our local areas. Typically maintained by the local phone company, this phone book is produced from the phone company’s customer records. If you don’t have a phone, you don’t show up in the book. But the book is incomplete and frequently out-of-date—we’ve all come to live with the possibility that the person or business’s phone number or address might be unlisted or have changed since the book was published.
Recently, a number of companies, affiliated with some of the larger communications companies, have begun publishing the information found in the phone book on the Internet. (See Figure 3.2.) These lookup services are typically not much better than the printed phone book, since the information is not always updated as changes occur. Still, an on-line phone book lets us locate a hardware store in Atlanta from the comfort of our own home in Chicago.
Phone book information is generally organized into white pages and yellow pages. (Refer to Chapter 1 for a description of white pages and yellow pages types of infor- mation.) Whether we use the white pages or yellow pages depends on the type of search that we would like to perform against the information. Unlike the printed form of a phone book, a white pages lookup in an electronic directory is merely a dif- ferent type of search than a yellow pages lookup. In a hard-copy phone book, infor- mation is repeated on different pages of the book.
A variation of the phone book style directory is the library card catalog. A library card catalog provides information on how to locate books, periodicals, and reference infor- mation in a particular library. The Library of Congress Classification system is used to uniquely identify books in the library, and library shelves are ordered by the Library of Congress Classification system. The Library of Congress Classification system identi-
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fiers are hard for humans to remember, however, so a card catalog was created. The card catalog (and the electronic form of the card catalog) offer white pages and yellow pages forms of lookup for books in the library. The white pages lookup of a book is the portion of the card catalog that provides a search by title. The yellow pages lookup of a book offers two types of searches: by subject and by author. So while the yellow pages lookup in the phone book is by service offered, yellow pages lookups in the library can be performed by subject or by author. Like the phone book, hard-copy forms of the library card catalog are nightmares to maintain, since adding a book requires adding multiple cards to the card catalog. Removal of a book from circulation involves finding all the subject-based cards.
As companies have moved their corporate phone books into electronic form, mainte- nance of them has become much easier. Changes to an employee’s information can be controlled by the employee, the human resources department, the mail system adminis- trator, and the physical services administrator. But the corporate phone book is only one of the places where information about people and services is located. And even though the information might all be stored in electronic format, synchronization of this information with the multitude of other directories in the organization is a problem. Another form of the phone book style of a directory is the directory that is used to locate and contact other computers in a network of connected computers. Directo- ries of this form are typically tied to the particular network implementation, because naming and addressing computers over networks is highly dependent on the network implementation chosen. These directories handle name-based or white pages style lookups for computers in the network. Some of these directories also offer service- based lookups, which is more like a yellow pages style lookup.