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A directory service is similar to a database, organizing data into nodes and values. It catalogs different information depending on its focus, and can be read and written to but is usually read-only. Redundant information is allowed, and a project is necessary to avoid overload.
From the outside, a directory service looks like a large database. The directory supports a large amount of data and the data is organized by node and value. The directory service catalogs different information, depending on its focus. For example, a network directory service catalogs all resources on a computer, while a Domain Name System (DNS) directory catalogs Web sites. The differences between a directory and a database are that a directory can include redundant information, and directories are read rather than written, so many write commands are omitted.
A directory service looks just like a database. It holds similar data and organizes each data into a node and value format, just like some hierarchical and relational database models. The node in a directory is the primary information, while the value is a string of data attached to the node. If the directory were for an address book, the node would be a name, while the value would be a phone number corresponding to the name.
Directories can be built for many purposes. A network directory details all the software and hardware in a computer, but it rarely requires the user to know the directory or how to access the hardware or software. A DNS directory takes the website’s domain names and creates a number-based domain for the website, which is rarely seen by the user. Directory technology is versatile, but the directory should only be created for one purpose or information could conflict.
While similar to database models, a directory service has some major differences. In a database, if redundant or repeating information is stored in tables, it is possible for the database to accidentally link data that is truly unrelated or create programming problems. In a directory, information can be redundant. For example, a phone book may include multiple identical names, but the phone book will be able to differentiate between them based on different phone numbers.
A directory service can be read and written to, but more often than not it is read only. This causes many of the write commands present in database technology to not be included in directories. The rollback and transaction capabilities are limited, because the directory simply doesn’t need them.
Each directory service must include a project. This blueprint is a set of rules programmed into the directory that tell the directory what information is important, what it should collect, and what information to ignore. Without a project, a directory would try to absorb all the information, causing it to become overloaded.
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