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Clarify that directories are searchable and browsable databases,

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not just directories optimized for read access.  Categorize DNS as
a "lookup" service.  Give dmoz.org as an example of directory service.
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Kurt Zeilenga 2006-11-15 19:20:18 +00:00
parent ee0026ec1e
commit 2b269055c4
1 changed files with 30 additions and 16 deletions
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doc/guide/admin/intro.sdf
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@ -15,19 +15,25 @@ provided by {{slapd}}(8).
H2: What is a directory service? H2: What is a directory service?
A directory is a specialized database optimized for reading, browsing A directory is a specialized database specifically designed for
and searching. Directories tend to contain descriptive, attribute-based searching and browsing, in additional to supporting basic lookup
information and support sophisticated filtering capabilities. and update functions.
Directories generally do not support complicated transaction or
roll-back schemes found in database management systems designed Note: A directory is defined by some as merely a database optimized
for handling high-volume complex updates. Directory updates are for read access. This definition, at best, is overly simplistic.
typically simple all-or-nothing changes, if they are allowed at
all. Directories are tuned to give quick response to high-volume Directories tend to contain descriptive, attribute-based information
lookup or search operations. They may have the ability to replicate and support sophisticated filtering capabilities. Directories
information widely in order to increase availability and reliability, generally do not support complicated transaction or roll-back schemes
while reducing response time. When directory information is found in database management systems designed for handling high-volume
replicated, temporary inconsistencies between the replicas may be complex updates. Directory updates are typically simple all-or-nothing
okay, as long as they get in sync eventually. changes, if they are allowed at all. Directories are generally
tuned to give quick response to high-volume lookup or search
operations. They may have the ability to replicate information
widely in order to increase availability and reliability, while
reducing response time. When directory information is replicated,
temporary inconsistencies between the replicas may be okay, as long
as inconsistencies are resolved in a timely manner.
There are many different ways to provide a directory service. There are many different ways to provide a directory service.
Different methods allow different kinds of information to be stored Different methods allow different kinds of information to be stored
@ -41,9 +47,17 @@ services are usually {{distributed}}, meaning that the data they
contain is spread across many machines, all of which cooperate to contain is spread across many machines, all of which cooperate to
provide the directory service. Typically a global service defines provide the directory service. Typically a global service defines
a uniform {{namespace}} which gives the same view of the data no a uniform {{namespace}} which gives the same view of the data no
matter where you are in relation to the data itself. The Internet matter where you are in relation to the data itself.
{{TERM[expand]DNS}} (DNS) is an example of a globally distributed
directory service. A web directory, such as provided by the Open Directory Project
<{{URL:http://dmoz.org}}>, is a good example of a directory service.
These services catalog web pages and are specifically designed to
support browsing and searching.
While some consider the Internet {{TERM[expand]DNS}} (DNS) is an
example of a globally distributed directory service, DNS is not
browsable nor searchable. It is more properly described as a
globaly distributed {{lookup}} service.
H2: What is LDAP? H2: What is LDAP?