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1.6 +<head>
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1.8 + <title>Sessions and Persistent Information</title>
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1.12 +</head>
1.13 +<body>
1.14 +<h1>Sessions and Persistent Information</h1>
1.15 +<p>The term "session" is a technical term describing information which
1.16 +is remembered by an application for a particular user. Sessions work in
1.17 +conjunction which other mechanisms - typically <a href="cookies.html">cookies</a>
1.18 +and <a href="users.html">user identifiers</a> - like this:</p>
1.19 +<ol>
1.20 + <li> The application finds out who the user is - this information may
1.21 +be recorded in a <a href="cookies.html">cookie</a> or be associated
1.22 +with a request in <a href="users.html">some other way</a>.</li>
1.23 + <li>It then accesses a data store containing information associated
1.24 +different users.</li>
1.25 + <li>Finally, it accesses information specific to the stated user -
1.26 +this is that particular user's session.</li>
1.27 +</ol>
1.28 +<h2>Sessions vs. Persistent Information</h2>
1.29 +<p>Information can be said to be "persistent" when it is
1.30 +remembered beyond the lifetime of a particular request to an
1.31 +application. Sessions, meanwhile, are effectively a special case of
1.32 +persistent information - data is addressed or accessed using each
1.33 +user's identity, and the information is partitioned in such a way that
1.34 +sessions cannot be shared between users.</p>
1.35 +<table style="text-align: left; width: 80%;" align="center" border="1"
1.36 + cellpadding="5" cellspacing="0" width="80%">
1.37 + <tbody>
1.38 + <tr>
1.39 + <td></td>
1.40 + <th style="text-align: center;">Sessions</th>
1.41 + <th style="text-align: center;">Persistent Information</th>
1.42 + </tr>
1.43 + <tr>
1.44 + <th>Access</th>
1.45 + <td align="undefined" valign="undefined">Through user identity.</td>
1.46 + <td align="undefined" valign="undefined">Through any relevant
1.47 +concept: users, documents, orders, products, locations - anything an
1.48 +application might want to remember.</td>
1.49 + </tr>
1.50 + <tr>
1.51 + <th>Partitioning</th>
1.52 + <td align="undefined" valign="undefined">By user identity. Each
1.53 +user has its own private data store.</td>
1.54 + <td align="undefined" valign="undefined">Arbitrary. Many data
1.55 +stores or data sources may be set up. The data may be shared across the
1.56 +entire application or there may be access controls in place.</td>
1.57 + </tr>
1.58 + </tbody>
1.59 +</table>
1.60 +<p>Access to persistent information in general can be done by using
1.61 +database access libraries, for example - see <a href="integrating.html">"Integrating
1.62 +with Other Systems"</a> for more details. </p>
1.63 +<h2>More About Sessions</h2>
1.64 +<ul>
1.65 + <li><a href="sessions-usage.html">Using Sessions</a></li>
1.66 + <li><a href="sessions-servers.html">Server Environment Support for
1.67 +Sessions</a></li>
1.68 +</ul>
1.69 +</body>
1.70 +</html>