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8 <title>Glossary - Apache HTTP Server</title>
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14 <p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p>
15 <p class="apache">Apache HTTP Server Version 2.1</p>
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17 <div class="up"><a href="./"><img title="<-" alt="<-" src="./images/left.gif" /></a></div>
19 <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="./">Version 2.1</a></div><div id="page-content"><div id="preamble"><h1>Glossary</h1>
21 <p><span>Available Languages: </span><a href="./de/glossary.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
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27 <p>This glossary defines some of the common terminology related to Apache in
28 particular, and web serving in general. More information on each concept
29 is provided in the links.</p>
31 <div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
33 <h2><a name="definitions" id="definitions">Definitions</a></h2>
36 <dt><a name="accesscontrol" id="accesscontrol">Access Control</a></dt>
37 <dd>The restriction of access to network realms. In an Apache context
38 usually the restriction of access to certain <em>URLs</em>.<br /> See: <a href="howto/auth.html">Authentication, Authorization, and Access
42 <dt><a name="algorithm" id="algorithm">Algorithm</a></dt>
44 <dd>An unambiguous formula or set of rules for solving a problem in a finite
45 number of steps. Algorithms for encryption are usually called
49 <dt><a name="apacheextensiontool" id="apacheextensiontool">APache
50 eXtension Tool</a> <a name="apxs" id="apxs">(apxs)</a></dt>
51 <dd>A perl script that aids in compiling <span title="see glossary">→</span> <a href="./glossary.html#module">module</a> sources into Dynamic Shared Objects
52 (<span title="see glossary">→</span> <a href="./glossary.html#dso">DSO</a>s) and helps install them in the
53 Apache Web server.<br />
54 See: Manual Page: <code class="program"><a href="./programs/apxs.html">apxs</a></code>
57 <dt><a name="authentication" id="authentication">Authentication</a></dt>
58 <dd>The positive identification of a network entity such as a server, a
59 client, or a user.<br />
60 See: <a href="howto/auth.html">Authentication, Authorization, and Access
64 <dt><a name="certificate" id="certificate">Certificate</a></dt>
65 <dd>A data record used for authenticating network entities such
66 as a server or a client. A certificate contains X.509 information pieces
67 about its owner (called the subject) and the signing <span title="see glossary">→</span> <a href="./glossary.html#certificationauthority">Certification Authority</a> (called
68 the issuer), plus the owner's <span title="see glossary">→</span> <a href="./glossary.html#publickey">public
70 signature made by the CA. Network entities verify these signatures
71 using CA certificates.<br />
72 See: <a href="ssl/">SSL/TLS Encryption</a>
75 <dt><a name="certificatsigningrequest" id="certificatsigningrequest">Certificate Signing Request</a>
76 <a name="csr" id="csr">(CSR)</a></dt>
77 <dd>An unsigned <span title="see glossary">→</span> <a href="./glossary.html#certificate">certificate</a> for
78 submission to a <span title="see glossary">→</span> <a href="./glossary.html#certificationauthority">Certification
79 Authority</a>, which signs it with the <span title="see glossary">→</span> <a href="./glossary.html#privatekey">Private Key</a> of their CA
80 <em>Certificate</em>. Once the CSR is signed, it becomes a real
82 See: <a href="ssl/">SSL/TLS Encryption</a>
85 <dt><a name="certificationauthority" id="certificationauthority">Certification Authority</a>
86 <a name="ca" id="ca">(CA)</a></dt>
87 <dd>A trusted third party whose purpose is to sign certificates for network
88 entities it has authenticated using secure means. Other network entities
89 can check the signature to verify that a CA has authenticated the bearer
90 of a certificate.<br />
91 See: <a href="ssl/">SSL/TLS Encryption</a>
94 <dt><a name="cipher" id="cipher">Cipher</a></dt>
95 <dd>An algorithm or system for data encryption. Examples are DES, IDEA, RC4,
97 See: <a href="ssl/">SSL/TLS Encryption</a>
100 <dt><a name="ciphertext" id="ciphertext">Ciphertext</a></dt>
101 <dd>The result after <span title="see glossary">→</span> <a href="./glossary.html#plaintext">Plaintext</a> is
102 passed through a <span title="see glossary">→</span> <a href="./glossary.html#cipher">Cipher</a>.<br /> See: <a href="ssl/">SSL/TLS Encryption</a>
105 <dt><a name="commongatewayinterface" id="commongatewayinterface">Common
106 Gateway Interface</a> <a name="cgi" id="cgi">(CGI)</a></dt>
107 <dd>A standard definition for an interface between a web server and an
108 external program that allows the external program to service requests.
109 The interface was originally defined by <a href="http://hoohoo.ncsa.uiuc.edu/cgi/overview.html">NCSA</a> but there
110 is also an <a href="http://cgi-spec.golux.com/">RFC project</a>.<br />
111 See: <a href="howto/cgi.html">Dynamic Content with CGI</a>
114 <dt><a name="configurationdirective" id="configurationdirective">Configuration Directive</a></dt>
115 <dd>See: <span title="see glossary">→</span> <a href="./glossary.html#directive">Directive</a></dd>
117 <dt><a name="configurationfile" id="configurationfile">Configuration
119 <dd>A text file containing <span title="see glossary">→</span> <a href="./glossary.html#directive">Directives</a>
120 that control the configuration of Apache.<br />
121 See: <a href="configuring.html">Configuration Files</a>
124 <dt><a name="connect" id="connect">CONNECT</a></dt>
125 <dd>An HTTP <span title="see glossary">→</span> <a href="./glossary.html#method">method</a> for proxying raw data
126 channels over HTTP. It can be used to encapsulate other protocols, such as
130 <dt><a name="context" id="context">Context</a></dt>
131 <dd>An area in the <span title="see glossary">→</span> <a href="./glossary.html#configurationfile">configuration
132 files</a> where certain types of <span title="see glossary">→</span> <a href="./glossary.html#directive">directives</a> are allowed.<br />
133 See: <a href="mod/directive-dict.html#Context">Terms Used to Describe
134 Apache Directives</a>
137 <dt><a name="digitalsignature" id="digitalsignature">Digital
139 <dd>An encrypted text block that validates a certificate or other file. A
140 <span title="see glossary">→</span> <a href="./glossary.html#certificationauthority">Certification Authority</a>
141 creates a signature by generating a hash of the <em>Public Key</em>
142 embedded in a <em>Certificate</em>, then encrypting the hash with its own
143 <em>Private Key</em>. Only the CA's public key can decrypt the signature,
144 verifying that the CA has authenticated the network entity that owns the
145 <em>Certificate</em>.<br />
146 See: <a href="ssl/">SSL/TLS Encryption</a>
149 <dt><a name="directive" id="directive">Directive</a></dt>
150 <dd>A configuration command that controls one or more aspects of Apache's
151 behavior. Directives are placed in the <span title="see glossary">→</span> <a href="./glossary.html#configurationfile">Configuration File</a><br />
152 See: <a href="mod/directives.html">Directive Index</a>
155 <dt><a name="dynamicsharedobject" id="dynamicsharedobject">Dynamic
156 Shared Object</a> <a name="dso" id="dso">(DSO)</a></dt>
157 <dd><span title="see glossary">→</span> <a href="./glossary.html#module">Modules</a> compiled separately from the
158 Apache <code class="program"><a href="./programs/httpd.html">httpd</a></code> binary that can be loaded on-demand.<br />
159 See: <a href="dso.html">Dynamic Shared Object Support</a>
162 <dt><a name="environmentvariable" id="environmentvariable">Environment
163 Variable</a> <a name="env-variable" id="env-variable">(env-variable)</a></dt>
164 <dd>Named variables managed by the operating system shell and used to store
165 information and communicate between programs. Apache also contains
166 internal variables that are referred to as environment variables, but are
167 stored in internal Apache structures, rather than in the shell
169 See: <a href="env.html">Environment Variables in Apache</a>
172 <dt><a name="export-crippled" id="export-crippled">Export-Crippled</a></dt>
173 <dd>Diminished in cryptographic strength (and security) in order to comply
174 with the United States' Export Administration Regulations (EAR).
175 Export-crippled cryptographic software is limited to a small key size,
176 resulting in <em>Ciphertext</em> which usually can be decrypted by brute
178 See: <a href="ssl/">SSL/TLS Encryption</a>
181 <dt><a name="filter" id="filter">Filter</a></dt>
182 <dd>A process that is applied to data that is sent or received by the
183 server. Input filters process data sent by the client to the server,
184 while output filters process documents on the server before they are sent
185 to the client. For example, the <code>INCLUDES</code> output filter
186 processes documents for <span title="see glossary">→</span> <a href="./glossary.html#ssi">Server Side
188 See: <a href="filter.html">Filters</a>
191 <dt><a name="fully-qualifieddomain-name" id="fully-qualifieddomain-name">Fully-Qualified Domain-Name</a>
192 <a name="fqdn" id="fqdn">(FQDN)</a></dt>
193 <dd>The unique name of a network entity, consisting of a hostname and a
194 domain name that can resolve to an IP address. For example,
195 <code>www</code> is a hostname, <code>example.com</code> is a domain name,
196 and <code>www.example.com</code> is a fully-qualified domain name.
199 <dt><a name="handler" id="handler">Handler</a></dt>
200 <dd>An internal Apache representation of the action to be performed when a
201 file is called. Generally, files have implicit handlers, based on the file
202 type. Normally, all files are simply served by the server, but certain
203 file types are "handled" separately. For example, the
204 <code>cgi-script</code> handler designates files to be processed as
205 <span title="see glossary">→</span> <a href="./glossary.html#cgi">CGIs</a>.<br />
206 See: <a href="handler.html">Apache's Handler Use</a>
209 <dt><a name="hash" id="hash">Hash</a></dt>
210 <dd>A mathematical one-way, irreversable algorithm generating a string with
211 fixed-length from another string of any length. Different input strings
212 will usually produce different hashes (depending on the hash function).
215 <dt><a name="header" id="header">Header</a></dt>
216 <dd>The part of the <span title="see glossary">→</span> <a href="./glossary.html#http">HTTP</a> request and
217 response that is sent before the actual content, and that contains
218 meta-information describing the content.
221 <dt><a name="htaccess" id="htaccess">.htaccess</a></dt>
222 <dd>A <span title="see glossary">→</span> <a href="./glossary.html#configurationfile">configuration file</a> that
223 is placed inside the web tree and applies configuration <span title="see glossary">→</span> <a href="./glossary.html#directive">directives</a> to the directory where it is
224 placed and all sub-directories. Despite its name, this file can hold
225 almost any type of directive, not just access-control directives.<br />
226 See: <a href="configuring.html">Configuration Files</a>
229 <dt><a name="httpd.conf" id="httpd.conf">httpd.conf</a></dt>
230 <dd>The main Apache <span title="see glossary">→</span> <a href="./glossary.html#configurationfile">configuration
231 file</a>. The default location is
232 <code>/usr/local/apache2/conf/httpd.conf</code>, but it may be moved using
233 run-time or compile-time configuration.<br />
234 See: <a href="configuring.html">Configuration Files</a>
237 <dt><a name="hypertexttransferprotocol" id="hypertexttransferprotocol">HyperText Transfer Protocol</a>
238 <a name="http" id="hhtp">(HTTP)</a></dt>
239 <dd>The standard transmission protocol used on the World Wide Web. Apache
240 implements version 1.1 of the protocol, referred to as HTTP/1.1 and
241 defined by <a href="http://ietf.org/rfc/rfc2616.txt">RFC 2616</a>.
244 <dt><a name="https" id="https">HTTPS</a></dt>
245 <dd>The HyperText Transfer Protocol (Secure), the standard encrypted
246 communication mechanism on the World Wide Web. This is actually just HTTP
247 over <span title="see glossary">→</span> <a href="./glossary.html#ssl">SSL</a>.<br />
248 See: <a href="ssl/">SSL/TLS Encryption</a>
251 <dt><a name="method" id="method">Method</a></dt>
252 <dd>In the context of <span title="see glossary">→</span> <a href="./glossary.html#http">HTTP</a>, an action to
253 perform on a resource, specified on the request line by the client. Some
254 of the methods available in HTTP are <code>GET</code>, <code>POST</code>,
255 and <code>PUT</code>.
258 <dt><a name="messagedigest" id="messagedigest">Message Digest</a></dt>
259 <dd>A hash of a message, which can be used to verify that the contents of
260 the message have not been altered in transit.<br />
261 See: <a href="ssl/">SSL/TLS Encryption</a>
264 <dt><a name="mime-type" id="mime-type">MIME-type</a></dt>
265 <dd>A way to describe the kind of document being transmitted. Its name
266 comes from that fact that its format is borrowed from the Multipurpose
267 Internet Mail Extensions. It consists of a major type and a minor type,
268 separated by a slash. Some examples are <code>text/html</code>,
269 <code>image/gif</code>, and <code>application/octet-stream</code>. In
270 HTTP, the MIME-type is transmitted in the <code>Content-Type</code>
271 <span title="see glossary">→</span> <a href="./glossary.html#header">header</a>.<br />
272 See: <a href="mod/mod_mime.html">mod_mime</a>
275 <dt><a name="module" id="module">Module</a></dt>
276 <dd>An independent part of a program. Much of Apache's functionality is
277 contained in modules that you can choose to include or exclude. Modules
278 that are compiled into the Apache <code class="program"><a href="./programs/httpd.html">httpd</a></code> binary are
279 called <dfn>static modules</dfn>, while modules that are stored
280 separately and can be optionally loaded at run-time are called
281 <dfn>dynamic modules</dfn> or <span title="see glossary">→</span> <a href="./glossary.html#dso">DSOs</a>.
282 Modules that are included by default
283 are called <dfn>base modules</dfn>. Many modules are available for Apache
284 that are not distributed as part of the Apache HTTP Server <span title="see glossary">→</span> <a href="./glossary.html#tarball">tarball</a>. These are referred to as
285 <dfn>third-party modules</dfn>.<br />
286 See: <a href="mod/">Module Index</a>
289 <dt><a name="modulemagicnumber" id="modulemagicnumber">Module Magic
290 Number</a> (<a name="mmn" id="mmn">MMN</a>)</dt>
291 <dd>Module Magic Number is a constant defined in the Apache source code that
292 is associated with binary compatibility of modules. It is changed when
293 internal Apache structures, function calls and other significant parts of
294 API change in such a way that binary compatibility cannot be guaranteed
295 any more. On MMN change, all third party modules have to be at least
296 recompiled, sometimes even slightly changed in order to work with the new
300 <dt><a name="openssl" id="openssl">OpenSSL</a></dt>
301 <dd>The Open Source toolkit for SSL/TLS<br />
302 See <a href="http://www.openssl.org/">http://www.openssl.org/</a>#
305 <dt><a name="passphrase" id="passphrase">Pass Phrase</a></dt>
306 <dd>The word or phrase that protects private key files. It prevents
307 unauthorized users from encrypting them. Usually it's just the secret
308 encryption/decryption key used for <span title="see glossary">→</span> <a href="./glossary.html#cipher">Ciphers</a>.<br />
309 See: <a href="ssl/">SSL/TLS Encryption</a>
312 <dt><a name="plaintext" id="plaintext">Plaintext</a></dt>
313 <dd>The unencrypted text.</dd>
315 <dt><a name="privatekey" id="privatekey">Private Key</a></dt>
316 <dd>The secret key in a <span title="see glossary">→</span> <a href="./glossary.html#publickeycryptography">Public Key
317 Cryptography</a> system, used to decrypt incoming messages and
318 sign outgoing ones.<br />
319 See: <a href="ssl/">SSL/TLS Encryption</a>
322 <dt><a name="proxy" id="proxy">Proxy</a></dt>
323 <dd>An intermediate server that sits between the client and the <em>origin
324 server</em>. It accepts requests from clients, transmits those requests
325 on to the origin server, and then returns the response from the origin
326 server to the client. If several clients request the same content, the
327 proxy can deliver that content from its cache, rather than requesting it
328 from the origin server each time, thereby reducing response time.<br />
329 See: <a href="mod/mod_proxy.html">mod_proxy</a>
332 <dt><a name="publickey" id="publickey">Public Key</a></dt>
333 <dd>The publicly available key in a <span title="see glossary">→</span> <a href="./glossary.html#publickeycryptography">Public Key Cryptography</a> system,
334 used to encrypt messages bound for its owner and to decrypt signatures
335 made by its owner.<br />
336 See: <a href="ssl/">SSL/TLS Encryption</a>
339 <dt><a name="publickeycryptography" id="publickeycryptography">Public Key Cryptography</a></dt>
340 <dd>The study and application of asymmetric encryption systems, which use
341 one key for encryption and another for decryption. A corresponding pair of
342 such keys constitutes a key pair. Also called Asymmetric Cryptography.
344 See: <a href="ssl/">SSL/TLS Encryption</a>
347 <dt><a name="regularexpresion" id="regularexpresion">Regular Expression</a>
348 <a name="regex" id="regex">(Regex)</a></dt>
349 <dd>A way of describing a pattern in text - for example, "all the words that
350 begin with the letter A" or "every 10-digit phone number" or even "Every
351 sentence with two commas in it, and no capital letter Q". Regular
352 expressions are useful in Apache because they let you apply certain
353 attributes against collections of files or resources in very flexible ways
354 - for example, all .gif and .jpg files under any "images" directory could
355 be written as "<code>/images/.*(jpg|gif)$</code>". Apache uses Perl
356 Compatible Regular Expressions provided by the <a href="http://www.pcre.org/">PCRE</a> library.
359 <dt><a name="reverseproxy" id="reverseproxy">Reverse Proxy</a></dt>
360 <dd>A <span title="see glossary">→</span> <a href="./glossary.html#proxy">proxy</a> server that appears to the client
361 as if it is an <em>origin server</em>. This is useful to hide the real
362 origin server from the client for security reasons, or to load balance.
365 <dt><a name="securesocketslayer" id="securesocketslayer">Secure Sockets
366 Layer</a> <a name="ssl" id="ssl">(SSL)</a></dt>
367 <dd>A protocol created by Netscape Communications Corporation for general
368 communication authentication and encryption over TCP/IP networks. The most
369 popular usage is <em>HTTPS</em>, i.e. the HyperText Transfer Protocol (HTTP)
371 See: <a href="ssl/">SSL/TLS Encryption</a>
374 <dt><a name="serversideincludes" id="serversideincludes">Server Side
375 Includes</a> <a name="ssi" id="ssi">(SSI)</a></dt>
376 <dd>A technique for embedding processing directives inside HTML files.<br />
377 See: <a href="howto/ssi.html">Introduction to Server Side Includes</a>
380 <dt><a name="session" id="session">Session</a></dt>
381 <dd>The context information of a communication in general.</dd>
383 <dt><a name="ssleay" id="ssleay">SSLeay</a></dt>
384 <dd>The original SSL/TLS implementation library developed by Eric A.
388 <dt><a name="symmetriccryptophraphy" id="symmetriccryptophraphy">Symmetric
389 Cryptography</a></dt>
390 <dd>The study and application of <em>Ciphers</em> that use a single secret key
391 for both encryption and decryption operations.<br />
392 See: <a href="ssl/">SSL/TLS Encryption</a>
395 <dt><a name="tarball" id="tarball">Tarball</a></dt>
396 <dd>A package of files gathered together using the <code>tar</code> utility.
397 Apache distributions are stored in compressed tar archives or using
401 <dt><a name="transportlayersecurity" id="transportlayersecurity">Transport
402 Layer Security</a> <a name="tls" id="tls">(TLS)</a></dt>
403 <dd>The successor protocol to SSL, created by the Internet Engineering Task
404 Force (IETF) for general communication authentication and encryption over
405 TCP/IP networks. TLS version 1 and is nearly identical with SSL version
407 See: <a href="ssl/">SSL/TLS Encryption</a>
410 <dt><a name="uniformresourcelocator" id="uniformresourcelocator">Uniform
411 Resource Locator</a> <a name="url" id="url">(URL)</a></dt>
412 <dd>The name/address of a resource on the Internet. This is the common
413 informal term for what is formally called a <span title="see glossary">→</span> <a href="./glossary.html#uniformresourceidentifier">Uniform Resource Identifier</a>.
414 URLs are usually made up of a scheme, like <code>http</code> or
415 <code>https</code>, a hostname, and a path. A URL for this page is
416 <code>http://httpd.apache.org/docs-2.1/glossary.html</code>.
419 <dt><a name="uniformresourceidentifier" id="uniformresourceidentifier">Uniform Resource Identifier</a>
420 <a name="URI" id="URI">(URI)</a></dt>
421 <dd>A compact string of characters for identifying an abstract or physical
422 resource. It is formally defined by <a href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>. URIs used on the
423 world-wide web are commonly referred to as <span title="see glossary">→</span> <a href="./glossary.html#url">URLs</a>.
426 <dt><a name="virtualhosting" id="virtualhosting">Virtual Hosting</a></dt>
427 <dd>Serving multiple websites using a single instance of Apache. <em>IP
428 virtual hosting</em> differentiates between websites based on their IP
429 address, while <em>name-based virtual hosting</em> uses only the name of the
430 host and can therefore host many sites on the same IP address.<br />
431 See: <a href="vhosts/">Apache Virtual Host documentation</a>
434 <dt><a name="x.509" id="x.509">X.509</a></dt>
435 <dd>An authentication certificate scheme recommended by the International
436 Telecommunication Union (ITU-T) which is used for SSL/TLS authentication.<br /> See: <a href="ssl/">SSL/TLS Encryption</a>
440 <div class="bottomlang">
441 <p><span>Available Languages: </span><a href="./de/glossary.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
442 <a href="./en/glossary.html" title="English"> en </a> |
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445 </div><div id="footer">
446 <p class="apache">Copyright 1995-2005 The Apache Software Foundation or its licensors, as applicable.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
447 <p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p></div>
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