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-
- <manualpage metafile="glossary.xml.meta">
-
- <title>Glossary</title>
-
- <summary>
- <p>This glossary defines some of the common terminology related to
- Apache in particular, and web serving in general. More information
- on each concept is provided in the links.</p>
- </summary>
-
- <section id="definitions"><title>Definitions</title>
-
- <dl>
- <dt><a name="authentication">Authentication</a></dt> <dd>The positive
- identification of a network entity such as a server, a client, or a
- user.<br /> See: <a
- href="howto/auth.html">Authentication, Authorization, and Access
- Control</a></dd>
-
- <dt><a name="accesscontrol">Access Control</a></dt>
- <dd>The restriction of access to network realms. In an Apache context
- usually the restriction of access to certain <em>URLs</em>.<br />
- See: <a
- href="howto/auth.html">Authentication, Authorization, and Access
- Control</a></dd>
-
- <dt><a name="algorithm">Algorithm</a></dt>
- <dd>An unambiguous formula or set of rules for solving a problem in
- a finite number of steps. Algorithms for encryption are usually called
- <dfn>Ciphers</dfn>.</dd>
-
- <dt><a name="apacheextensiontool">APache eXtension Tool</a> <a
- name="apxs">(apxs)</a></dt> <dd>A perl script that aids in compiling <a
- href="#module">module</a> sources into Dynamic Shared Objects (<a
- href="#dso">DSO</a>s) and helps install them in the Apache Web
- server.<br /> See: <a
- href="programs/apxs.html">Manual Page: apxs</a></dd>
-
- <dt><a name="certificate">Certificate</a></dt>
- <dd>A data record used for authenticating network entities such
- as a server or a client. A certificate contains X.509 information pieces
- about its owner (called the subject) and the signing <a
- href="#certificationauthority">Certification Authority</a> (called the
- issuer), plus the owner's <a href="#publickey">public key</a> and the
- signature made by the CA. Network entities verify these signatures
- using CA certificates.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="certificationauthority">Certification Authority</a> <a
- name="ca">(CA)</a></dt> <dd>A trusted third party whose purpose is to
- sign certificates for network entities it has authenticated using
- secure means. Other network entities can check the signature to verify
- that a CA has authenticated the bearer of a certificate.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="certificatsigningrequest">Certificate Signing Request</a>
- <a name="csr">(CSR)</a></dt> <dd>An unsigned <a
- href="#certificate">certificate</a> for submission to a <a
- href="#certificationauthority">Certification Authority</a>, which signs it
- with the <a href="#privatekey">Private Key</a> of their CA
- <em>Certificate</em>. Once the CSR is signed, it becomes a real
- certificate.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
-
- <dt><a name="cipher">Cipher</a></dt> <dd>An algorithm or system for
- data encryption. Examples are DES, IDEA, RC4, etc.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="ciphertext">Ciphertext</a></dt> <dd>The result after <a
- href="#plaintext">Plaintext</a> is passed through a <a
- href="#cipher">Cipher</a>.<br /> See: <a href="ssl/">SSL/TLS
- Encryption</a></dd>
-
- <dt><a name="commongatewayinterface">Common Gateway Interface</a> <a
- name="cgi">(CGI)</a></dt> <dd>A standard definition for an interface
- between a web server and an external program that allows the external
- program to service requests. The interface was originally defined by
- <a href="http://hoohoo.ncsa.uiuc.edu/cgi/overview.html">NCSA</a> but
- there is also an <a href="http://cgi-spec.golux.com/">RFC
- project</a>.<br />
- See: <a href="howto/cgi.html">Dynamic Content with CGI</a></dd>
-
-
- <dt><a name="configurationdirective">Configuration Directive</a></dt>
- <dd>See: <a href="#directive">Directive</a></dd>
-
- <dt><a name="configurationfile">Configuration File</a></dt>
- <dd>A text file containing <a href="#directive">Directives</a>
- that control the configuration of Apache.<br />
- See: <a href="configuring.html">Configuration Files</a></dd>
-
- <dt><a name="connect">CONNECT</a></dt> <dd>An HTTP <a
- href="#method">method</a> for proxying raw data channels over HTTP. It
- can be used to encapsulate other protocols, such as the SSL
- protocol.</dd>
-
- <dt><a name="context">Context</a></dt> <dd>An area in the <a
- href="#configurationfile">configuration files</a> where certain types
- of <a href="#directive">directives</a> are allowed.<br /> See: <a
- href="mod/directive-dict.html#Context">Terms
- Used to Describe Apache Directives</a></dd>
-
- <dt><a name="digitalsignature">Digital Signature</a></dt>
- <dd>An encrypted text block that validates a certificate or other file. A
- <a href="#certificationauthority">Certification Authority</a> creates a
- signature by generating a hash of the <em>Public Key</em> embedded in a
- <em>Certificate</em>, then encrypting the hash with its own <em>Private
- Key</em>. Only the CA's public key can decrypt the signature, verifying
- that the CA has authenticated the network entity that owns the
- <em>Certificate</em>.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="directive">Directive</a></dt> <dd>A configuration command
- that controls one or more aspects of Apache's behavior. Directives
- are placed in the <a href="#configurationfile">Configuration
- File</a><br /> See: <a href="mod/directives.html">Directive
- Index</a></dd>
-
- <dt><a name="dynamicsharedobject">Dynamic Shared Object</a> <a
- name="dso">(DSO)</a></dt> <dd><a href="#module">Modules</a> compiled
- separately from the Apache httpd binary that can be loaded on-demand.<br />
- See: <a href="dso.html">Dynamic Shared Object Support</a></dd>
-
- <dt><a name="environmentvariable">Environment Variable</a> <a
- name="env-variable">(env-variable)</a></dt>
- <dd>Named variables managed by the operating system shell
- and used to store information and communicate between programs. Apache also
- contains internal variables that are referred to as environment variables,
- but are stored in internal Apache structures, rather than in the
- shell environment.<br />
- See: <a href="env.html">Environment Variables in Apache</a></dd>
-
- <dt><a name="export-crippled">Export-Crippled</a></dt>
- <dd>Diminished in cryptographic strength (and security) in order to comply
- with the United States' Export Administration Regulations (EAR).
- Export-crippled cryptographic software is limited to a small key size,
- resulting in <em>Ciphertext</em> which usually can be decrypted by brute
- force.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="filter">Filter</a></dt> <dd>A process that is applied to
- data that is sent or received by the server. Input filters process
- data sent by the client to the server, while output filters process
- documents on the server before they are sent to the client. For
- example, the <code>INCLUDES</code> output filter processes documents
- for <a href="#ssi">Server Side Includes</a>.<br /> See: <a
- href="filter.html">Filters</a></dd>
-
- <dt><a name="fully-qualifieddomain-name">Fully-Qualified
- Domain-Name</a> <a name="fqdn">(FQDN)</a></dt> <dd>The unique name of
- a network entity, consisting of a hostname and a domain name that can
- resolve to an IP address. For example, <code>www</code> is a hostname,
- <code>example.com</code> is a domain name, and
- <code>www.example.com</code> is a fully-qualified domain name.</dd>
-
- <dt><a name="handler">Handler</a></dt> <dd>An internal Apache
- representation of the action to be performed when a file is
- called. Generally, files have implicit handlers, based on the file
- type. Normally, all files are simply served by the server, but certain
- file types are "handled" separately. For example, the
- <code>cgi-script</code> handler designates files to be processed as <a
- href="#cgi">CGIs</a>.<br />
- See: <a href="handler.html">Apache's Handler Use</a></dd>
-
- <dt><a name="header">Header</a></dt>
- <dd>The part of the <a href="#http">HTTP</a> request and response that
- is sent before the actual content, and that contains meta-information
- describing the content.</dd>
-
- <dt><a name=".htaccess">.htaccess</a></dt> <dd>A <a
- href="#configurationfile">configuration file</a> that is placed inside
- the web tree and applies configuration <a
- href="#directive">directives</a> to the directory where it is placed
- and all sub-directories. Despite its name, this file can hold almost
- any type of directive, not just access-control directives.<br />
- See: <a href="configuring.html">Configuration Files</a></dd>
-
- <dt><a name="httpd.conf">httpd.conf</a></dt>
- <dd>The main Apache <a href="#configurationfile">configuration file</a>.
- The default location is <code>/usr/local/apache2/conf/httpd.conf</code>,
- but it may be moved using run-time or compile-time configuration.<br />
- See: <a href="configuring.html">Configuration Files</a></dd>
-
- <dt><a name="hypertexttransferprotocol">HyperText Transfer
- Protocol</a> <a name="http">(HTTP)</a></dt> <dd>The standard
- transmission protocol used on the World Wide Web. Apache implements
- version 1.1 of the protocol, referred to as HTTP/1.1 and defined by <a
- href="http://ietf.org/rfc/rfc2616.txt">RFC 2616</a>.</dd>
-
- <dt><a name="https">HTTPS</a></dt>
- <dd>The HyperText Transfer Protocol (Secure), the standard encrypted
- communication mechanism on the World Wide Web. This is actually just HTTP
- over <a href="#ssl">SSL</a>.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="method">Method</a></dt> <dd>In the context of <a
- href="#http">HTTP</a>, an action to perform on a resource, specified
- on the request line by the client. Some of the methods available in
- HTTP are <code>GET</code>, <code>POST</code>, and <code>PUT</code>.</dd>
-
- <dt><a name="messagedigest">Message Digest</a></dt>
- <dd>A hash of a message, which can be used to verify that the contents of
- the message have not been altered in transit.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="mime-type">MIME-type</a></dt> <dd>A way to describe the
- kind of document being transmitted. Its name comes from that fact
- that its format is borrowed from the Multipurpose Internet Mail
- Extensions. It consists of a major type and a minor type, separated
- by a slash. Some examples are <code>text/html</code>,
- <code>image/gif</code>, and <code>application/octet-stream</code>. In
- HTTP, the MIME-type is transmitted in the <code>Content-Type</code> <a
- href="#header">header</a>.<br /> See: <a
- href="mod/mod_mime.html">mod_mime</a></dd>
-
- <dt><a name="module">Module</a></dt> <dd>An independent part of a
- program. Much of Apache's functionality is contained in modules that
- you can choose to include or exclude. Modules that are compiled into
- the Apache httpd binary are called <em>static modules</em>, while
- modules that are stored separately and can be optionally loaded at
- run-time are called <em>dynamic modules</em> or <a
- href="#dso">DSOs</a>. Modules that are included by default are called
- <em>base modules</em>. Many modules are available for Apache that are
- not distributed as part of the Apache HTTP Server <a
- href="#tarball">tarball</a>. These are referred to as <em>third-party
- modules</em>.<br />
- See: <a href="mod/">Module Index</a></dd>
-
- <dt><a name="modulemagicnumber">Module Magic Number</a> (<a
- name="mmn">MMN</a>)</dt>
- <dd>
- Module Magic Number is a constant defined in the Apache source code
- that is associated with binary compatibility of modules. It is changed
- when internal Apache structures, function calls and other significant
- parts of API change in such a way that binary compatibility cannot be
- guaranteed any more. On MMN change, all third party modules have to be
- at least recompiled, sometimes even slightly changed in order to work
- with the new version of Apache.
- </dd>
-
- <dt><a name="openssl">OpenSSL</a></dt>
- <dd>The Open Source toolkit for SSL/TLS<br />
- see <a href="http://www.openssl.org/">http://www.openssl.org/</a></dd>
-
- <dt><a name="passphrase">Pass Phrase</a></dt> <dd>The word or phrase
- that protects private key files. It prevents unauthorized users from
- encrypting them. Usually it's just the secret encryption/decryption
- key used for <a name="cipher">Ciphers</a>.<br /> See: <a
- href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="plaintext">Plaintext</a></dt>
- <dd>The unencrypted text.</dd>
-
- <dt><a name="privatekey">Private Key</a></dt> <dd>The secret key in a
- <a name="publickeycryptography">Public Key Cryptography</a> system,
- used to decrypt incoming messages and sign outgoing ones.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="proxy">Proxy</a></dt> <dd>An intermediate server that
- sits between the client and the <em>origin server</em>. It accepts
- requests from clients, transmits those requests on to the origin
- server, and then returns the response from the origin server to the
- client. If several clients request the same content, the proxy
- can deliver that content from its cache, rather than requesting it
- from the origin server each time, thereby reducing response time.<br />
- See: <a href="mod/mod_proxy.html">mod_proxy</a></dd>
-
- <dt><a name="publickey">Public Key</a></dt> <dd>The publicly
- available key in a <a name="publickeycryptography">Public Key
- Cryptography</a> system, used to encrypt messages bound for its owner
- and to decrypt signatures made by its owner.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="publickeycryptography">Public Key Cryptography</a></dt>
- <dd>The study and application of asymmetric encryption systems, which
- use one key for encryption and another for decryption. A corresponding
- pair of such keys constitutes a key pair. Also called Asymmetric
- Cryptography.<br /> See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="regularexpresion">Regular Expression</a> <a
- name="regex">(Regex)</a></dt> <dd>A way of
- describing a pattern in text - for example, "all the words that begin with the
- letter A" or "every 10-digit phone number" or even "Every sentence
- with two commas in it, and no capital letter Q". Regular expressions
- are useful in Apache because they let you apply certain
- attributes against collections of files or resources in very flexible
- ways - for example, all .gif and .jpg files under any "images"
- directory could be written as "<code>/images/.*(jpg|gif)$</code>".
- Apache uses Perl Compatible Regular Expressions provided by the
- <a href="http://www.pcre.org/">PCRE</a> library.</dd>
-
- <dt><a name="reverseproxy">Reverse Proxy</a></dt> <dd>A <a
- href="#proxy">proxy</a> server that appears to the client as if it is
- an <em>origin server</em>. This is useful to hide the real origin
- server from the client for security reasons, or to load balance.</dd>
-
- <dt><a name="securesocketslayer">Secure Sockets Layer</a> <a
- name="ssl">(SSL)</a></dt> <dd>A protocol created by Netscape
- Communications Corporation for general communication authentication
- and encryption over TCP/IP networks. The most popular usage is
- <em>HTTPS</em>, i.e. the HyperText Transfer Protocol (HTTP) over SSL.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="serversideincludes">Server Side Includes</a> <a
- name="ssi">(SSI)</a></dt> <dd>A technique for embedding processing
- directives inside HTML files.<br /> See: <a
- href="howto/ssi.html">Introduction to Server Side Includes</a></dd>
-
- <dt><a name="session">Session</a></dt>
- <dd>The context information of a communication in general.</dd>
-
- <dt><a name="ssleay">SSLeay</a></dt>
- <dd>The original SSL/TLS implementation library developed by
- Eric A. Young</dd>
-
- <dt><a name="symmetriccryptophraphy">Symmetric Cryptography</a></dt>
- <dd>The study and application of <em>Ciphers</em> that use a single secret key
- for both encryption and decryption operations.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="tarball">Tarball</a></dt>
- <dd>A package of files gathered together using the <code>tar</code>
- utility. Apache distributions are stored in compressed tar archives
- or using pkzip.</dd>
-
- <dt><a name="transportlayersecurity">Transport Layer Security</a> <a
- name="tls">(TLS)</a></dt> <dd>The successor protocol to SSL, created
- by the Internet Engineering Task Force (IETF) for general
- communication authentication and encryption over TCP/IP networks. TLS
- version 1 and is nearly identical with SSL version 3.<br />
- See: <a href="ssl/">SSL/TLS Encryption</a></dd>
-
- <dt><a name="uniformresourcelocator">Uniform Resource Locator</a> <a
- name="url">(URL)</a></dt> <dd>The name/address of a resource on the
- Internet. This is the common informal term for what is formally
- called a <a href="#uniformresourceidentifier">Uniform Resource
- Identifier</a>. URLs are usually made up of a scheme, like
- <code>http</code> or <code>https</code>, a hostname, and a path. A
- URL for this page is
- <code>http://httpd.apache.org/docs-2.0/glossary.html</code>.</dd>
-
- <dt><a name="uniformresourceidentifier">Uniform Resource Identifier</a> <a
- name="URI">(URI)</a></dt> <dd>A compact string of characters for
- identifying an abstract or physical resource. It is formally defined
- by <a href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>.
- URIs used on the world-wide web are commonly referred to
- as <a href="#url">URLs</a>.</dd>
-
- <dt><a name="virtualhosting">Virtual Hosting</a></dt> <dd>Serving
- multiple websites using a single instance of Apache. <em>IP virtual
- hosting</em> differentiates between websites based on their IP
- address, while <em>name-based virtual hosting</em> uses only the name
- of the host and can therefore host many sites on the same IP
- address.<br /> See: <a href="vhosts/">Apache Virtual Host
- documentation</a></dd>
-
- <dt><a name="x.509">X.509</a></dt> <dd>An authentication certificate
- scheme recommended by the International Telecommunication Union
- (ITU-T) which is used for SSL/TLS authentication.<br /> See: <a
- href="ssl/">SSL/TLS Encryption</a></dd>
-
- </dl>
- </section>
- </manualpage>
-