php文件中用于creat Mysql的chema是什么意思?

hguoh163

define('SCHEMA', 'mysql');

$phrasegroups = array();
$specialtemplates = array();

// Check userfield table is still used and how long the default length should be

$schema['CREATE']['query']['access'] = "
CREATE TABLE " . TABLE_PREFIX . "access (
        userid int unsigned NOT NULL DEFAULT '0',
        forumid smallint unsigned NOT NULL DEFAULT '0',
        accessmask smallint unsigned NOT NULL DEFAULT '0',
        PRIMARY KEY userid (userid, forumid)
)
";
这里的chema是什么?